The skeptical cardiologist has been pointing out for some time that dietary advice to universally restrict consumption of saturated fats is not scientifically based.
Different foods present different types of saturated fats in different matrices and it is not reasonable to assume the overall effect of these foods can be predicted by measuring only saturated fat content.
In particular, there is not a scintilla of evidence that proves dairy fat which contains significant amounts of saturated fat has any harmful cardiovascular consequences. Thus, attempts to advise Americans to consume low fat or non-fat dairy are horribly misguided.
As I wrote in my letter to the FDA and in a recent critique of the AHA “the suggestion to restrict or eliminate full-fat dairy from the diet is not a proven strategy for reducing the risk of cardiovascular disease, obesity or diabetes and should be eliminated from current dietary guidelines.”
I encourage a full reading of the article but here is the abstract:
“across the board recommendation to limit dietary saturated fatty acid (SFA) intake has persisted despite mounting evidence to the contrary. Most recent meta-analyses of randomized trials and observational studies found no beneficial effects of reducing SFA intake on cardiovascular disease (CVD) and total mortality, and instead found protective effects against stroke. Although SFAs increase low-density lipoprotein (LDL)-cholesterol, in most individuals, this is not due to increasing levels of small, dense LDL particles, but rather larger LDL which are much less strongly related to CVD risk. It is also apparent that the health effects of foods cannot be predicted by their content in any nutrient group, without considering the overall macronutrient distribution. Whole-fat dairy, unprocessed meat, eggs and dark chocolate are SFA-rich foods with a complex matrix that are not associated with increased risk of CVD. The totality of available evidence does not support further limiting the intake of such foods.“
Hopefully, the Committee discussing the next version of the Dietary Guidelines for Americans are objectively examining the extensive scientific literature that led to these conclusions.
It is important to look at industry influence on research and publications (along with other biases) but it is hard to find an expert in these areas who hasn’t had some industry ties. Part of these ties develop because researchers who have concluded a particular food is healthy based on their independent review of the literature will be sought after as a speaker at conferences organized by the support groups for that food.
Fortunately, my evaluations remain unsullied by any food industry ties and, like Dr. Astrup,(lead author on the JACC review) I am not an advocate or activist for specific diets and I am not not strongly committed to any specific diet.
Three years ago I carefully researched the details of the death of Robert Atkins and wrote about it on this blog. I was motivated by the grossly inaccurate portrayal of him promulgated on vegan and plant-based websites. Elsewhere on this website I have described in detail the death of Nathan Pritikin whose ultra-low fat diet stands in stark contrast to Atkins’ ultra-low carb diet.
The most important point I hoped to make was that we should not judge the benefits of any diet based on how the founder of that diet dies. There is far too much randomness in death and far too much genetic influence over our health to base dietary decisions on one man ( or woman’s) mode of departing existence.
Atkins suffered a completely random event slipping and falling on ice and suffering an epidural hematoma. Pritikin developed leukemia and died after committing suicide.
Unfortunately my article did not end the misinformation rampant on the internet about Atkins so I’m reposting it today for all of you who may be feeling guilty about eating too much on Thanksgiving yesterday.
One of the characters in my story, Michael Bloomberg, has recently announced that he is running for President.
In the spring of 2003 at the age of 72 years, Robert Atkins, the cardiologist and controversial promoter of high fat diets for weight loss, fell on the sidewalk in front of his Atkins Center for Complementary Medicine in Manhattan. He lost his footing on a patch of ice, slipped and banged his head on the pavement. At the time of his fall his book ”Dr. Atkins’ New Diet Revolution” lead the NY times paper-back best seller list.
He was taken to nearby Cornell Medical Center where a clot was evacuated from his brain. Thereafter he lapsed into a coma and he spent 9 days in the ICU, expiring on April 17, 2003.
The cause of death was determined by the New York Medical Examiner to be “blunt injury of head with epidural hematoma.”
An epidural hematoma is a collection of blood between the skull and the tough outer lining of the brain (the dura) which can occur with blunt trauma to the head which results in laceration of the arteries in this area. It is a not uncommon cause of death in trauma . Actress Natasha Richardson (skiing, see below) died from this. Nothing about the manner in which Robert Atkins died would suggest that he was a victim of his own diet any more than Natasha Richardson was.
However, within the year a campaign of misinformation and deception spear-headed by evangelistic vegans would try to paint the picture that Atkins died as a direct result of what they perceived as a horribly dangerous diet.
Michael Bloomberg, then New York major, was quoted as saying
“I don’t believe that bullshit that [Atkins] dropped dead slipping on the sidewalk.”
“The 61-year-old billionaire added that Atkins was “fat” and served “inedible” food at his Hamptons home when Bloomberg visited. The mayor’s inference, of course, was that Atkins was actually felled by his meat-heavy diet, that his arteries were clogged with beef drippings. “
Enter The Vegans
Richard Fleming, a physician promoting prevention of cardiovascular disease through vegetarianism and with close ties to an organization called Physicians Committe for Responsible Medicine (PCRM) sent a letter to the NY Medical Examiner requesting a copy of the full medical examination of Atkins. The NYME office should have only issued copies of this report to physicians involved in the care of Atkins or next of kin but mistakenly complied with this request. Fleming, who would subsequently publish his own low fat diet book, conveniently gave the report to PCRM which is directed by animal rights and vegan physicians.
Neal Barnard, the President of PCRM, in an incredibly unethical move sent the letter to the Wall Street Journal with the hope that the information would destroy the popularity of the Atkins diet, a diet he clearly despises.. Barnard said the group decided to publicize the report because Atkins’ “health history was used to promote his terribly unhealthy eating plan..” The WSJ subsequently published an article summarizing the findings.
To this day, advocates of vegetarianism and low fat diets, distort the findings of Atkins’ Medical Examination in order to depict high fat diets like his as dangerous and portray Atkins as a victim of his own diet.
To scientists and thoughtful, unbiased physicians it is manifestly apparent that you cannot base decisions on what diet plan is healthy or effective for weight loss on the outcome of one patient. It doesn’t matter how famous that one person is or whether he/she originated and meticulously followed the diet. It is a ludicrous concept.
Would you base your decision to engage in running based on the death of Jim Fixx? Fixx did much to popularize the sport of running and the concept of jogging as a source of health benefit and weight loss. He died while jogging, in fact. An autopsy concluded that he died of a massive heart attack and found advanced atherosclerosis (blockage) of the arteries to his heart.
Would you based your decision to engage in a very low fat diet based on how Nathan Pritikin died? Pritikin authored an extremely popular book emphasizing eliminating fat from the diet but developed leukemia and slashed his wrists, committing suicide at the age of 69 years. Would vegetarians accept the premise that their preferred diet results in leukemia or suicidal depression based on Pritikin’s death?
The Distortion of Atkins Death
The NYME report lists Atkins weight at autopsy as 258 pounds. Low-fat zealots seized on this fact as indicating that Atkins was morbidly obese throughout his life. For example, a you-tube video of an audio interview of Atkinas online posted by “plant-based coach” has this obviously photoshopped head of Atkins put on the body of a morbidly obese man. Atkins actually weight around 200 pounds through most of his life and a hospital note on admission showed him weighing 195 pounds. A substantial weight gain of 63 pounds occurred in the 9 days after his admission due to the accumulation of fluid volume and swelling which is not uncommon in the critically ill.
No autopsy was performed on Atkins but the NYME wrote on the document that he had “h/o of MI, CHF, HTN.”
MI is the acronym for a myocardial infarction or heart attack. As far as we can tell without access to full medical records, Atkins never had an MI. He did have a cardiac arrest in 2002. While most cardiac arrests are due to a cardiac arrhythmia secondary to an MI they can also occur in patients who have a cardiomyopathy or weakness in the heart muscle from causes other than MI.
In fact, USA Today reported that Stuart Trager, MD, chairman of the Atkins Physicians Council in New York, indicated that Atkins was diagnosed with a cardiomyopathy at the time of his cardiac arrest and that it was not felt to be due to blocked coronary arteries/MI. Cardiomyopathy can be caused by viral infections or nonspecific inflammation of the heart muscle and would have nothing to do with diet.
Trager also stated that Atkins, as a result of the cardiomyopathy, had developed heart failure (CHF) and the pumping ability of his heart (ejection fraction) had dropped to 15% to 20%. While CHF can be due to heart attacks causing heart weakness in Atkins case it appears it was unrelated to fatty blockage of the coronary arteries causing MI and therefore likely not related to his diet.
What Does Atkins Death Tell Us About His Diet
The information about Atkins death tells us nothing about the effectiveness or dangers of his diet. In one individual it is entirely likely that a genetic predisposition to cancer or heart disease overwhelms whatever beneficial effects the individual’s lifestyle may have had. Thus, we should never rely on the appearance or the longevity of the primary promoter of a diet for the diet’s effectiveness.
The evangelists of low-fat, vegan or vegetarian diets like PCRM have shamelessly promoted misinformation about Atkins death to dismiss high fat diets and promote their own agenda. If their diets are truly superior it should be possible to utilize facts and science to promote them rather than a sensationalistic, distorted focus on the body of one man who slipped on the ice and fell to his death.
She notes that publication of these yogurt papers was paid for by a big player in the yogurt industry:
These three papers were part of a supplement to Advances in Nutrition published in September 2019: Supplement—6th Yogurt in Nutrition Initiative (YINI) Summit / More than the Sum of Its Parts, sponsored by Danone Institutes International. Publication costs for this supplement were defrayed in part by the payment of page charges.
Yes, these three papers were published in a supplement sponsored by the yogurt industry and therefore must be taken with a grain of salt.
However, a totally unbiased look at the data on yogurt and cardiovascular disease which I have provided here and here comes to the same conclusion. Misguided attempts to make full fat yogurt healthier by eliminating dairy fat have created artificial sugar-laden monstrosities which are actually stealth desserts.
It’s interesting that the dairy industry has been complicit in promoting the idea that low fat dairy is healthier because (as I pointed out here) it allows them to double dip the milk cash cow-skimming off the healthy fat and selling the separated fat and the residual skim milk separately.
The second paper ( Dairy Foods, Obesity, and Metabolic Health: The Role of the Food Matrix Compared with Single Nutrients) was based on a talk that Dariush Mozaffarian gave at the American Society of Nutrition 2018 Congress. I’ve been following Mozaffarian’s work since 2012 and I consider him to be an excellent researcher, writer and thinker who can be trusted to present unbiased information. The content of that talk presented by him at a national scientific congress in front of his academic colleagues is unlikely to be biased.
Here is what he concludes:
“The present evidence suggests that whole-fat dairy foods do not cause weight gain, that overall dairy consumption increases lean body mass and reduces body fat, that yogurt consumption and probiotics reduce weight gain, that fermented dairy consumption including cheese is linked to lower CVD risk, and that yogurt, cheese, and even dairy fat may protect against type 2 diabetes. Based on the current science, dairy consumption is part of a healthy diet, without strong evidence to favor reduced-fat products; while intakes of probiotic-containing unsweetened and fermented dairy products such as yogurt and cheese appear especially beneficial.”
It’s important to look at the disclosures for any scientific paper and Mozzafarian has a lot of industry ties to disclose:
“DM received an honorarium from the American Society of Nutrition for the preparation of this manuscript. A freelance science writer, Denise Webb, was supported by Danone Institute International to prepare an initial draft of this manuscript for DM based on a recording of his talk and slides at the American Society of Nutrition 2018 Congress. The final manuscript was edited in detail and approved by DM. The funders had no role in the design, analysis, interpretation, review, or final approval of the manuscript for publication…DM reports research funding from the NIH and the Gates Foundation; personal fees from GOED, Nutrition Impact, Pollock Communications, Bunge, Indigo Agriculture, Amarin, Acasti Pharma, Cleveland Clinic Foundation, and America’s Test Kitchen; scientific advisory board, Elysium Health (with stock options), Omada Health, and DayTwo; and chapter royalties from UpToDate; all outside the submitted work.”
“Although more research is warranted to adjust for possible confounding factors and to better understand the mechanisms of action of dairy products on health outcomes, it becomes increasingly clear that the recommendation to restrict dietary saturated fat to reduce risk of cardiometabolic disease is getting outdated. Therefore, the suggestion to restrict or eliminate full-fat dairy from the diet may not be the optimal strategy for reducing cardiometabolic disease risk and should be re-evaluated in light of recent evidence.”
His disclosures are extensive but they reveal how wide-ranging his interests are and how dedicated he is to optimizing diet.
AA is a member of advisory boards/consultant for BioCare Copenhagen, Denmark; Dutch Beer Institute, Netherlands; Gelesis, United States; Groupe Éthique et Santé, France; McCain Foods Limited, United States; Novo Nordisk, Denmark; Pfizer, United States; Saniona, Denmark; and Weight Watchers, United States. AA has received travel grants and honoraria as a speaker for a wide range of Danish and international consortia. AA is co-owner and member of the board of the consultancy company Dentacom Aps, Denmark; cofounder and co-owner of UCPH spin-outs Mobile Fitness A/S, Flaxslim ApS, and Personalized Weight Management Research Consortium ApS (Gluco-diet.dk). He is coinventor of a number of patents owned by the University of Copenhagen, in accordance with Danish law. He is coauthor of a number of diet and cookery books, including books on personalized diet approaches. AA is not an advocate or activist for specific diets and is not strongly committed to any specific diet.”
I love what he says at the end of his disclosure statement
“AA is not an advocate or activist for specific diets and is not strongly committed to any specific diet.”
Hooray! That is exactly what we need in the world of dietary recommendations.
I am particularly heartened by the conclusions of these two illustrious international nutritional authorities who have managed to cut through the long-standing nutritional dogma that all saturated fat is bad. As one who has no ties to any food or medical industry group and who is not an advocate or activitist for specific diets I concluded as they have that
Based on the current science, dairy consumption is part of a healthy diet, without strong evidence to favor reduced-fat products; while intakes of probiotic-containing unsweetened and fermented dairy products such as yogurt and cheese appear especially beneficial.”
It becomes increasingly clear that the recommendation to restrict dietary saturated fat to reduce risk of cardiometabolic disease is getting outdated. Therefore, the suggestion to restrict or eliminate full-fat dairy from the diet may not be the optimal strategy for reducing cardiometabolic disease risk and should be re-evaluated in light of recent evidence.”
As I wrote in my letter to the FDA and in a recent critique of the AHA I would change the verbiage to “the suggestion to restrict or eliminate full-fat dairy from the diet is not a proven strategy for reducing the risk of cardiovascular disease, obesity or diabetes and should be eliminated from current dietary guidelines.”
Two key points that these papers help emphasize:
Eating fat doesn’t make you fat
All saturated fat is not bad for your heart
It is important to look at industry influence on research and publications (along with other biases) but it is hard to find an expert in these areas who hasn’t had some industry ties. Part of these ties develop because researchers who have concluded a particular food is healthy based on their independent review of the literature will be sought after as a speaker at conferences organized by the support groups for that food.
Fortunately, my evaluations remain unsullied by any food industry ties and, like Dr. Astrup, I am not an advocate or activist for specific diets and I am not not strongly committed to any specific diet.
N.B. Trader’s Point Creamery Yogurt no longer distributes their wonderful products. I’ve started consuming Maple Hill 100% grass fed full fat yogurt and it is quite good.
N.B. #2.Arne Astrup’s bio.
Prof. Arne Astrup is Head of the Department of Nutrition, Exercise and Sports at the University of Copenhagen, and Senior Consultant at Clinical Research Unit, Herlev-Gentofte University Hospital. Astrup attained his medical degree from UCPH in 1982 and a Doctorate in Medical Science in 1986. He was Appointed Professor of Nutrition and Head of the Research Department of Human Nutrition at The Royal Veterinary and Agricultural University, Denmark, in 1990, he led the department throughout its development ever since.
His researches focus on the physiology and pathophysiology of energy and substrate metabolism and appetite regulation, with special emphasis on the etiology and treatment of obesity, including the role of diet composition and of specific nutrients, lifestyle modification, very-low-calorie diets, exercise, and medication. Major research collaborations include participation in the EU multicenter studies.
He led research that showed that GLP-1 is a satiety hormone in humans, and was instrumental in Denmark being the first country to ban industrial trans-fat in 2014. He is author/co-author of over 600 original, review and editorial scientific papers and more than 1000 other academic publications such as abstracts, textbook chapters and scientific correspondence. He has supervised 32 PhD students to date.
The skeptical cardiologist this morning was greeted by headlines announcing that an international panel of 14 unbiased researchers had concluded that it was OK for humans to continue eating red meat and processed meat at current levels.
The startling news was a reversal of what the Dietary Guidelines for Americans, the AHA and the American Cancer Society have been telling us for years and threw the nutritional world into a tizzy. The bottom line recommendation, written in language suggesting a lack of certainty in the evidence and lack of confidence in the advice reads as follows:
The panel suggests that adults continue current unprocessed red meat consumption (weak recommendation, low-certainty evidence). Similarly, the panel suggests adults continue current processed meat consumption (weak recommendation, low-certainty evidence).
Volluz does her typically excellent job of explaining the science in a balanced way and includes some of the prominent voices who are outraged by the publication.
As I’ve pointed out (here and here and here) the science behind most nutritional recommendations is weak and often public health authorities make sweeping dietary recommendations that aren’t justified.
We are making gradual progress in rolling back bans on some healthy food, like eggs but unjustified bans on other healthy foods like full-fat yogurt and coconut oil persist.
When it comes to red meat consumption the systematic analyses reveal mild associations with poor health outcomes but these associations don’t prove causality and could easily be due to confounding factors or poor input data.
Thus, if you want to cut back your red meat consumption on the chance that these associations are truly reflective of causation go ahead. Especially if you have ethical or environmental concerns about production of red meat.
Just keep in mind that the calories you cut from less meat consumption should be replaced by more healthy nutrient-dense foods like non-starchy vegetables, nuts, dairy fat, avocado and olive oil and not by low quality carbs and ultra-processed food or you may be doing more harm than good.
The skeptical cardiologist admits to being a coffee snob and addict. For the last 10 years I’ve been using the Chemex system to brew my morning cup of Java. Once I consistently partook of Chemex pour-over coffee made from freshly ground, recently roasted quality coffee beans it was hard for me to enjoy any other kind. I find Starbucks coffee particularly loathsome.
Although numerous studies have established that coffee consumption is safe (assuming you are not adding titanium dioxide to your cup), the belief that it is bad for you persists in the majority of patients that I see.
Since today is National Coffee Day let me take this opportunity to reassure my patients and readers who consume the good brew that they are not harming their hearts.
The intro to this paper summarizes information known about coffee and cardiovascular disease (CVD). Although early observational studies suggested coffee could increase risks:
More recent meta‐analysis of prospective studies showed that moderate coffee consumption was associated with decreased CVD risk, all‐cause mortality, and mortality attributed to CVD and neurologic disease in the overall population. High coffee consumption (>5 cups/d) was neither related to CVD risk nor to risk of mortality.12, To corroborate this evidence, the 2015–2020 Dietary Guidelines for Americans show that consumption of 3 to 5 cups/d of coffee is associated with reduced risk of type 2 diabetes mellitus and CVD in adults. Consequently, moderate coffee consumption can be incorporated into a healthy dietary pattern, along with other healthful behaviors. Although coffee consumption has been studied in relation to various risk factors of CVD, only 4 studies have investigated the association between coffee intake and subclinical atherosclerosis, and the data available were limited and inconsistent.
Coffee is rich in phenolic compounds which have demonstrated anti-inflammatory, antioxidant and antithrombotic properties which could lower cardiovascular risks. However, unfiltered coffee is rich in cholesterol‐raising compounds (diterpenes, kahweol, and cafestol) that can increase total cholesterol, low‐density lipoprotein cholesterol, and triglycerides.which could worsen cardiovascular risk.
Consumption of filtered coffee however does not effect lipid levels adversely- presumably those nasty diterpenes are retained by my Chemex filter.
The Brazilian Longitudinal study looked at 4426 residents of Sao Paulo, Brazil who underwent a CAC measurement. Information on coffee consumption was obtained from a food frequency questionnairre.
Those who reported high coffee consumption (>3 cups per day) had one-third the chance of a CAC>100 than nondrinkers. More coffee=less plaque build up in the coronary arteries. Less atherosclerotic plaque should = less heart attacks and strokes.
Scientific Consensus On The Healthiness of Coffee Consumption
In contrast to what the public believes, the scientific evidence very consistently suggests that drinking coffee is associated with living longer and having less heart attacks and strokes. Multiple publications in major cardiology journals in the last few years have confirmed this.
You can read the details here and here. The bottom line is that higher levels of coffee consumption (>1 cup per day in the US and >2 cups per day in Europe) are NOTassociated with:
Hypertension (if you are a habitual consumer)
Higher total or bad cholesterol (unless you consume unfiltered coffee like Turkish, Greek or French Press types, which allow a fair amount of the cholesterol-raising diterpenesinto the brew)
Increase in dangerous (atrial fibrillation/ventricular tachycardia) or benign (premature ventricular or supra-ventricular contractions) irregularities in heart rhythm
Higher levels of coffee consumption compared to no or lower levels IS associated with:
lower risk of Type 2 Diabetes
lower risk of dying, more specifically lower mortality from cardiovascular disease
So, if you like coffee and it makes you feel good, drink it without guilt, there is nothing to suggest it is hurting your cardiovascular health. It’s a real food. These tend to be good for you.
N.B. The Chemex Coffeemaker was invented in 1941 by Dr. Peter Schlumbohm PhD. Made simply from non-porous, borosilicate glass and fastened with a wood collar and tie, it brews coffee without imparting any flavors of its own. On permanent display at MOMA NY and other fine museums, it is truly a work of art.
The caffeine in coffee can bring on palpitations. If you feel palpitations or other symptoms after consuming coffee you should lower the caffeine content or amount until you no longer experience troubling symptoms. Be guided by how you feel.
In the ongoing nutritional war between adherents of low-fat and low-carb diets, the skeptical cardiologist has generally weighed in on the side of lower carbs for weight loss and cardiovascular health.
Recently I stumbled across a good review on the scientific evidence of various popular diets for weight loss. Obesity and its health consequences are clearly increasing and impacting the cardiovascular health of millions. As such, as a cardiologist it would be great to have a one true diet that is best for weight loss for my patients.
Unfortunately, as I discussed in my analysis of the DIETFITS study there isn’t a one size fits all dietary silver bullet. This recent review does a good job of analyzing the data and has some nice graphics.
Here’s the first graphic which summarizes the food groups allowed for 7 of the most popular diets
Is there any food group we can all agree on?
Yes, the non-starchy vegetables!
Dr. P’s Heart Nuts come in a close second (outlier Ornish recommends “moderation”. Extreme outlier Esselsytn who eschews all oils forbids nuts.)
Interestingly, the only one of these diets that bans red meat, chicken, seafood and eggs is the Ornish diet which is basically a vegetarian diet (see here for the lack of science behind this diet.)
Is there any food group that we all agree should be avoided? If we exclude the outlier Ornish then there is unanimity that we should be avoiding added sugar and refined grains.
The second graphic nicely summarizes the macronutrient composition of these diets. The Atkins diet and ketogenic diets recommend less than 10% carbs whereas Ornish the outlier recommends less than 10% fat.
My recommended variation on the Mediterranean diet would lower the carb % to around 20% by avoiding starchy vegetables, most added sugar and most refined grains. I try to avoid ultra-processed foods completely. With this diet I am in some degree of ketosis (as measured by the fantastic Keyto device) most of the time although I’m not strictly following keto guidelines.
For example last night I had this delicious steak and smoked portabello quesadilla from Three Kings Pub. The tortilla alone contains about 40 grams of carbs, double the recommended amount for keto diets. I add elements of Three Kings Middle Eastern Sampler (Red pepper hummus, grilled eggplant relish, tzatziki, roasted head of garlic and dolmas. Served with grilled flatbread and an assortment of veggies) to get some of those universally acclaimed nonstarchy vegetables . I don’t utilize the balsamic reduction that is typically drizzled on the quesadilla because it tastes like pure sugar to me (sure enough it contains 11 grams of carbs)and I mostly avoid the grilled flatbread.
Variations on this type of intermittent fasting (periodic fasting or 5:2 diet, alternate-day fasting, time-restricted feeding, and religious fasting) have become popular. The review summarizes the science in this area as follows:
“There is growing evidence demonstrating the metabolic health benefits of IF. In rodents, these appear quite profound, whereas in humans they are sparse and need further investigation, especially in long-term studies. It has been suggested that IF does not produce superior weight loss in comparison with continuous calorie restriction plans , and there are limited data regarding other clinical outcomes such as diabetes, CVD, and cancer. IF diets seem safe and tolerable for adults…”
In other words, rats live longer with IF but we don’t know if humans do. If you find intermittent fasting helps you consume less calories through out the day and lose weight, go for it. For me fasting from 9 PM to late morning (typically 14-16 hours) give me greater energy and focus throughout the day and makes weight management simpler.
Conclusions: What Is The Best Diet For Weight Loss?
Both low carb and low fat fanatics will be disappointed in the conclusions of the review but I think it is reasonable:
There is no one most effective diet to promote weight loss. In the short term, high-protein, low-carbohydrate diets and intermittent fasting are suggested to promote greater weight loss and could be adopted as a jumpstart. However, owing to adverse effects, caution is required. In the long term, current evidence indicates that different diets promoted similar weight loss and adherence to diets will predict their success. Finally, it is fundamental to adopt a diet that creates a negative energy balance and focuses on good food quality to promote health.
The skeptical cardiologist has become more selective with regard to who he will accept as a new patient. In practical terms this means I now call patients who want to see me and discuss with them why they want to see me, how they were referred or heard about me, and what their expectations are.
This might seem a little odd but turns out to be an excellent way for me to meet and smooth entrance for these newbies into my practice and gather important records and recordings prior to the first visit.
Recently, when I asked one of these potential patients why they had sought me as their cardiologist, the wife told me that through her internet research she had gleaned that I was a “Keto-friendly Cardiologist.”
Given that I have challenged conventional dogma on the dangers of dietary saturated fat and cholesterol and have written about ketosis (see here and here) a few times on this blog and defended Dr. Atkins I do actually consider myself “keto-friendly”. However my prospective patient’s wife was not aware of the skeptical cardiologist as a blog writer.
How or why I was identified as Keto-friendly cardiologist was not clear.
I realized I needed to make it perfectly clear. It is now time to come out of the keto closet.
I am a “Keto-friendly cardiologist”!
I have dozens of patients who have been very successful using very low carb/high fat diets to help them lose weight and gain control of their diabetes and hypertension.
I don’t poo poo low carb high fat diets and I think they are vey compatible with a heart-healthy existence.
In fact, lately I’ve gone back to dabbling with a Keto Diet myself.
To aid me in the dabbling I have found a device called Keyto to be the key to success and understanding of my ketosis.
Keyto: Breath Sensor for Ketosis and Weight Loss
When I went back to dabbling with ketosis in early 2019 I was using the Keto-Mojo finger prick device to measure my blood levels of beta hydroxybutyrate. I liked the precision this offered compared to urine dip sticks but grew to dislike the need to prick my finger and create blood loss.
About a month ago I ordered I discovered the keto breath sensor KEYTO and have found since then that it wonderfully simplifies the process of being on a keto diet.
Keyto costs $99 and comes in a box the size of a video cassette case.
In the box is the sensor device, four blowing mouthpieces, a very simple user manual, a AAA battery and a cute little bag for carrying the device
Ethan Weiss, MD, a highly respected preventative cardiologist and founder of Keyto includes a welcoming message for users which summarizes the mission of Keyto:
We designed the Keyto program to help you over-achieve your weight loss and health goals. With the Keyto Breath Sensor in this box, and the Keyto App on your phone, you have the key to unlocking success. You’ll be eating delicious foods, losing weight, and many users even report an increase in energy and focus
Using Keyto Is Simple and Convenient
Getting started with Keyto is very easy: download the Keyto smartphone app, log in and follow the straightforward directions for pairing the breath sensor with the app.
Once paired via Bluetooth making measurements is easy. It’s important to understand the breathing technique needed and to facilitate this I strongly recommend watching the brief explanatory video Weiss has provided. Basically, you want to use a normal breath and blow for 10 seconds so that you are near the end of expiration when the device makes its recording.
To initiate a measurement you push the plus sign on the main “Journey” screen in the app then push the on button on the sensor.
Usually, if the sensor has been turned on and the app is activated the app immediately connects to the sensor, occasionally I have had to turn the sensor off and on again to initiated the connection.
At this point the sensor begins warming up, reaching a temperature of 400 degrees Fahrenheit over a period of about 80 seconds.
The app displays the progress and offers you the option of answering some questions about how you are feeling and doing on the keto diet.
I often take my BP while this is going on. Sometimes I read the New Yorker. Frequently I listen to Radiohead (Climbing Up The Walls). It takes a while. Pay attention, though. You don’t want to miss your blowing window and have to repeat the process.
The app will give you a warning about 10 seconds prior to the time you need to blow. The graph to the right appears when it is time to blow and you can view the sensors output as it tracks the acetone it is seeing over the 10 seconds that you blow.
At the end of the blow you wait a few seconds, eagerly awaiting your score. Will you be in Ketosis?
Finally, your score is revealed. In this case I was congratulated for being in light ketosis with a fat burn of “medium high.” The highest score is an 8.
You can add notes to the record of your score
If you blow a 6 the app tells you that your fat burn is high and that you are in ketosis: “metabolizing fat like a champion.”
Accuracy of Keyto
When I first began using Keyto I checked the Keyto numbers versus the beta hydroxybutyrate (BOHB) numbers I was simultaneously getting from my Keto-Mojo meter.
I found a Keyto 3 corresponded to 0.8 BOHB, a Keyto 4 to 0.9 BOHB, and a 5 to 1.0 BOHB. That was enough to convince me that the device was accurate and useful in measuring my level of ketosis.
Given that it is so convenient compared to a finger stick I have stopped using the Keto-Mojo completely.
My observations confirm what Weiss and Ray Wu, MD, the cofounders of Keyto describe in very lucid prose here.
In extensive user testing, Keyto is directionally consistent with the more accurate commercially available blood meter. Keyto and blood β-hydroxybutyrate trend directionally the same in the majority of cases. Both go up and down in similar magnitude at different ranges of ketosis. There are some differences which are likely due to biology – the kinetics of clearance of acetone and β-hydroxybutyrate are not identical.
Some of the differences are also likely due to how we designed the Keyto program. Our primary goal was to develop a system that would give users the information they need to know i.e. if they are in ketosis, which would ultimately help promote healthy behavior change. Therefore, we chose not to report acetone concentrations in PPM or to attempt to convert PPM to blood β-hydroxybutyrate (mmol/L). The Keyto Level system was simply more effective, motivating, and fun without adding complexity and false precision.
I can make multiple measurements throughout the day without worrying about the cost or the discomfort of a finger stick. The ability to make multiple measurements means that I am getting very rapid and frequent feed back on how my dietary and lifestyle choices are effecting my level of ketosis.
Warning! Because the device is so convenient-literally you can have it with you at all times-you may find yourself blowing into it excessively. This may irritate your friends and loved ones, especially those that aren’t on a keto diet.
Keyto is Legitimate
The Keyto website has an excellent introduction to the keto diet (keto 101) and has numerous other very helpful resources for those who seek to lose weight using the diet.
In general I get a good feeling of integrity and legitimacy from every aspect of the Keyto operation.
I have a tremendous professional respect for Ethan Weiss, the cardiologist behind Keyto. He’s very active on Twitter and is typically spot on with his comments. He’s done a podcast with Peter Attia which serves as an excellent summary of atherosclerosis and coronary artery disease. He does really good basic science research involving growth hormone.
Weiss is now doing his own podcast called Best Known Method by Keyto which I highly recommend. It is not, surprisingly, focused on the keto diet or the keyto brand but interviews thought leaders in cardiology like Ron Krauss and Lisa Rosenbaum.
If you want to read more about how the Keyto breath sensor works see here. This is a very clear and concise description of the science behind the device and it is complete with references.
Ultimately, although I consider myself a keto-friendly cardiologist, I’m most interested in the diet that helps my patients achieve and sustain their goals of weight loss and better health. For many this is the keto diet.
And for those who find the keto diet is optimal for their health I will be advising them to acquire a Keyto breath sensor and check out the programs Keyto offers to support their health goals.
Supporters of vegetarian/ultra low fat diets like to claim that there is solid scientific evidence of the cardiovascular benefits of their chosen diets.
To buttress these claims they will cite the studies of Esseslystn, Pritikin and Ornish.
I’ve previously discussed the bad science underlying the programs of Esselsystn and Pritikin but have only briefly touched on the inadequacy of Dean Ornish’s studies.
The Ornish website proclaims that their program is the first program “scientifically proven to undo (reverse) heart disease.” That’s a huge claim. If it were true, wouldn’t the Dietary Guidelines for Americans, the American Heart Association, and most cardiologists and nutrition experts be recommending it?
Who Is Dean Ornish?
Dean Ornish has an MD degree from Baylor University and trained in internal medicine but has no formal cardiology or nutrition training (although many internet sites including Wikipedia describe him as a cardiologist.)
Ornish, according to the Encyclopedia of World Biographies became depressed and suicidal in college and underwent psychotherapy “but it was only when he met the man who had helped his older sister overcome her debilitating migraine headaches that his own outlook vastly improved. Under the watch of his new mentor, Swami Satchidananda, Ornish began yoga, meditation, and a vegetarian diet, and even spent time at the Swami’s Virginia center.”
Dr. Ornish’s Program for Reversing Heart Disease® is the first program scientifically proven to “undo” (reverse) heart disease by making comprehensive lifestyle changes.
The Ornish claims are based on a study he performed between 1986 and 1992 which originally had 28 patients with coronary artery disease in an experimental arm and 20 in a control group. You can read the details of the one year results here.and the five year results here.
There are so many limitations to this study that the mind boggles that it was published in a reputable journal.
-Recruitment of patients.
193 patients with significant coronary lesions from coronary angiography were “identified” but only 93 “remained eligible.” These were “randomly” assigned to the experimental or control groups. Somehow , this randomization process assigned 53 to the experimental group and 40 to the usual-care control group.
If this were truly a 1:1 randomization the numbers would be equal and the baseline characteristics equal.
Only 23 of the 53 assigned to the experimental group agreed to participate and only 20 of the control group.
The control group was older, less likely to be employed and less educated.
“The primary reason for refusal in the experimental group was not wanting to undergo intensive lifestyle changes and/or not wanting a second coronary angiogram; control patients refused primarily because they did not want to undergo a second angiogram.”
In other words, all of the slackers were weeded out of the experimental group and all of the patients who were intensely motivated to change their lifestyle were weeded out of the control group. Gee, I wonder which group will do better?
The experimental patients received “intensive lifestyle changes (<10% fat whole foods vegetarian diet, aerobic exercise, stress management training, smoking cessation, group psychosocial support). The control group had none of the above.
Needless to say this was not blinded and the researchers definitely knew which patients were in which group.
Control-group patients were “not asked to make lifestyle changes, although they were free to do so.”
There is very little known about the 20 slackers in the control group. I can’t find basic information about them-crucial things like how many smoked or quit smoking or how many were on statin drugs.
Progression or regression of coronary artery lesions was assessed in both groups by quantitative coronary angiography (QCA) at baseline and after about a year.
QCA as a test for assessing coronary artery disease has a number of limitations and as a result is no longer utilized for this purpose in clinical trials. When investigators want to know if an intervention is improving CAD they use techniques such as intravascular ultraound or coronary CT angiography (see here) which allow measurement of total atherosclerotic plaque burden.
Rather than burden the reader with the details at this point I’ve included a discussion of this as an addendum.
Ornish has widely promoted this heavily flawed study as showing “reversal of heart disease” because at one year the average percent coronary artery stenosis by angiogram had dropped from 40% to 37.8% in the intensive lifestyle group and increased from 42.7% to 46.1% in the control patients.
The minimal diameter (meaning the tightest stenosis) changed from 1.64 mm at baseline in the experimental to 1.65 at one year. At 5 years the minimal diameter had increased another whopping .001 mm to 1.651.
In other words even if we overlook the huge methodologic flaws in the study the so-called “reversal” was minuscule.
Utlimately, dropping coronary artery blockages by <5 % doesn’t really matter unless that is also helping to prevent heart attacks or death or strokes or some outcome that really matters.
There were no significant differences between the groups at 5 years in hard events such as heart attack or death. In fact 2 of the experimental group died versus 1 of the control group by 5 years.
There were less stents and bypasses performed in the Ornish group but the decision to proceed to stent or bypass is notoriously capricious when performed outside the setting of acute MI. The patients in the experimental group under the guidance of Ornish and their Ornish counselors would be strongly motivated to do everything possible to avoid intervention.
I’ve gotten a lot of flack for humorously suggesting that Nathan Pritikin killed himself as a result of the austere no fat diet he consumed but the bottom line on any lifestyle change is both quality and quantity of life.
If you are miserable most days due to your rigid diet you might consider that life is no longer worth living
Ornish’s Lifestyle Intervention Is Not A Trial Of Diet …And Other Points
Although often cited as justification of ultralow fat diet, the Ornish Lifestyle trial doesn’t test diet alone.
It is a trial of multiple different interventions with frequent counseling and meetings to reinforce and guide patients.
The interventions included things that we know are really important for long term health-regular exercise, smoking cessation, and weight management. These factors alone could account for any differences in the outcome but they are easily adopted without becoming a vegetarian.
The patients who agreed to the experimental arm were a clearly highly motivated bunch who agreed to this really strict regimen. Even in this population there was a 25% drop out rate.
Since investigators clearly knew who the “experimental patients” were and they were clearly interested in good outcomes in these patients there is a high possibility of bias in reporting outcomes and referring for interventions.
Despite all the limitations the study does raise an interesting hypothesis. Should we all be eating vegan diets?
if Ornish really wanted to scientifically prove his approach he should have repeated it with much better methodology and much larger numbers.
Finally, this tiny study has never been reproduced at any other center.
Because of the small numbers, lack of true blinding, lack of hard outcomes and use of multiple modalities for lifestyle intervention, this study cannot be used to support the Ornish/Esselstyn/Pritikin dietary approach.
It most certainly doesn’t show that the Ornish Lifestyle Program “reverses heart disease.” Consequently, you will not find any evidence-based source of nutritional information or guideline (unless it has a vegan/vegetarian philosophy or is being funded by the Ornish/Pritikin lifestyle money-making machines) recommending these diets.
N.B.1 A recent paper on noninvasive assessment of atherosclerotic plaque has a great infographic which shows how coronary artery disease progresses and how and when in the progression various imaging modalities are able to detect plaque:
I’ve inserted a vertical red arrow which shows how IVUS detects very early atheroma whereas angiography (ICA, green line) only detects later plaque when it has started protruding into the lumen of the artery.
The paper notes that “Intravascular ultrasound (IVUS) constitutes the current gold standard for plaque quantification. Multiple studies using IVUS and other techniques have revealed a robust relation between statin therapy and plaque regression. In the ASTEROID trial coronary atheroma volume regressed by 6.8% during 24 months of high-intensity lipid therapy. A meta-analysis of IVUS trials including 7864 patients showed an association between plaque regression and decreased cardiovascular events.”
While I believe Ornish started off as a legitimate scientist several authors have pointed out that he has joined the ranks of pseudoscientific practiioners.
In the end, the problem is that Dr. Ornish has yoked his science to advocates of pseudoscience, such as Deepak Chopra and Rustum Roy. Why he’s done this, I don’t know. The reason could be common philosophy. It could be expedience. It could be any number of things. By doing so, however, Dr. Ornish has made a Faustian deal with the devil that may give him short-term notoriety now but virtually guarantees serious problems with his ultimately being taken seriously scientifically, as he is tainted by this association. Let me yet again reemphasize that this relabeling of diet, exercise, and lifestyle as somehow being “alternative” is nothing more than a Trojan Horse. Inside the horse is a whole lot of woo, pseudoscience and quackery such as homepathy, reiki, Hoxsey therapy, acid-base pseudoscience, Hulda Clark’s “zapper,” and many others,
Why would I eat breakfast if I am not hungry in order to lose weight? What constitutes breakfast? Is it the first meal you eat after sleeping? If so, wouldn’t any meal eaten after sleeping qualify even it is eaten in the afternoon? Is eating a donut first thing in the morning really healthier than eating nothing? Why would your first meal be more important than the last? isn’t it the content of what we eat that is important more than the timing?
Most of the studies on the proposed effect of breakfast on obesity (PEBO), I pointed out, are observational studies which cannot prove causality and the few, small prospective randomized studies don’t clearly support the hypothesis.
I suggested that PEBO comes from the breakfast food and cereal industry and should be ignored.
Writing an update on my post in 2015 I referenced Melanie Warner’s excellent book on the methods of the food industry entitled “Pandora’s Lunchbox”
“Walk down a cereal aisle today or go onto a brand’s Web site, and you will quickly learn that breakfast cereal is one of the healthiest ways to start the day, chock full of nutrients and containing minimal fat. “Made with wholesome grains,” says Kellogg’s on its Web site. “Kellogg’s cereals help your family start the morning with energy by delivering a number of vital, take-on-the-day nutrients—nutrients that many of us, especially children, otherwise might miss.” It sounds fantastic. But what you don’t often hear is that most of these “take-on-the-day” nutrients are synthetic versions added to the product, often sprayed on after processing. It’s nearly impossible to find a box of cereal in the supermarket that doesn’t have an alphabet soup of manufactured vitamins and minerals, unless you’re in the natural section, where about half the boxes are fortified.”
The Kellogg’s and General Mills of the world strongly promoted the concept that you shouldn’t skip breakfast because they had developed products that stayed fresh on shelves for incredibly long periods of time. They could be mixed with easily accessible (low-fat, no doubt) milk to create inexpensive, very quickly and easily made, ostensibly healthy breakfasts.
Unfortunately, the processing required to make these cereals last forever involved removing the healthy components.
As Warner writes about W.K. Kellogg:
“In 1905, he changed the Corn Flakes recipe in a critical way, eliminating the problematic corn germ, as well as the bran. He used only the starchy center, what he referred to as “the sweetheart of the corn,” personified on boxes by a farm girl clutching a freshly picked sheaf. This served to lengthen significantly the amount of time Corn Flakes could sit in warehouses or on grocers’ shelves but compromised the vitamins housed in the germ and the fiber residing in the bran”
The writer, Roni Rabin (who has a degree in journalism from Columbia University) struggles to support her sense that there is a “growing body of research” suggesting we should all modify our current dietary habits in order to eat a breakfast and make breakfast the largest meal of the day
Below are some of his scathing comments, taken from one of his non-lame weekly emails:
You’ve probably heard that breakfast is the most important meal of the day. “What is less commonly mentioned,” writes Alex Mayyasi in The Atlantic, “is the origin of this ode to breakfast: a 1944 marketing campaign launched by General Foods, the manufacturer of Grape Nuts, to sell more cereal.”
Seventy-five years later, here’s the latest report from the April issue of the Journal of the American College of Cardiology: “Taken together, these studies [showing a positive association between skipping breakfast and CVD and CVD risk factors] as well as our findings underscore the importance of eating breakfast as a simple way to promote cardiovascular health and prevent cardiovascular morbidity and mortality.”
What were the findings? Let’s look at a few newspapers:
“Want to Lower Your Risk for Heart Disease? Eat Breakfast Every Morning” (Healthline)
“Eating breakfast? Skipping a morning meal has higher risk of heart-related death, study says” (USA TODAY)
“Study: Skipping breakfast increases risk of heart disease mortality by 87 percent (FOX)”
(You may notice that all three headlines imply causality.)
Looks like General Foods was right. Time to reach for the Lucky Charms? Perhaps it’s time to put on our critical thinking cap instead. The actual study, and the media coverage of it, is a part of the Groundhog Day that is observational epidemiology (for more on the limitations of this type of research, check out Studying Studies: Part II). This was a prospective cohort study pulling data from NHANES III, looking at people who reportedly eat breakfast every day to people who never eat breakfast, and then following up with them (about 19 years later on average), tallying up the deaths from CVD and deaths from all causes.
One question to ask about the population studied is: was eating breakfast or not eating breakfast the only difference between these two groups? In other words, were there any confounding factors (for more on confounding, see Studying Studies: Part IV)? The authors reported that, “participants who never consumed breakfast were more likely to be non-Hispanic black, former smokers, heavy drinkers, unmarried, physically inactive, and with less family income, lower total energy intake, and poorer dietary quality, when compared with those who regularly ate breakfast.” Not only that, “participants who never consumed breakfast were more likely to have obesity, and higher total blood cholesterol level than those who consumed breakfast regularly.” They also had a higher reported incidence of diabetes and dyslipidemia. Read that again, please.
While the study used statistical models to “adjust for” many of these potential confounders, it’s extremely difficult (actually, it’s impossible) to accurately and appropriately adjust for what amounts to fundamentally different people. The healthy user bias (or the inverse, an unhealthy user bias) is virtually impossible to tease out of these studies (the healthy user bias is covered in more depth in Studying Studies: Part I). Not only that, you never really know what you’re not looking for. This is typically referred to as residual confounding in the literature, where other factors may be playing a role that go unmeasured by the investigators.
I haven’t even yet mentioned the misleading nature of reporting relative risk — in this case, an associated 87% (reported in the study as a hazard ratio of 1.87) — without reporting absolute risk. The question you should always ask is, 87% greater than what? To get an idea of the associated absolute risk, the number of CVD deaths in the “every day” breakfast group were 415 out of a total of 3,862 people over 16.7 years (that’s an unadjusted rate of 10.7%) while the numbers for the “never” breakfast folks were 41 CVD deaths out of a total of 336 people over 16.7 years (unadjusted rate of 12.2%). That’s an absolute difference of 1.5% over almost 17 years (annually, this is an absolute difference of 0.09%). Granted, this is before adjustment of the myriad confounders (including the biggest “risk factor” for CVD death, age, in which the “never” breakfast group was younger on average at baseline), but it gives you an idea that we’re looking at small differences even over the course of a couple of decades. This looks a lot difference on paper than an associated 87% increased risk of CVD death. (For more on absolute risk and relative risk, see Studying Studies: Part I.)
What were the participants actually eating for breakfast? We don’t know. The investigators didn’t have information about what foods and beverages they consumed.
Did participants change their breakfast eating (or abstaining) habits over the course of almost 20 years? We don’t know. Information on breakfast eating was only collected at baseline.
Could there be errors in the classification of the causes of death in the participants? It’s possible.
What constitutes skipping breakfast? Was it the timing of the first meal of the day? We don’t know. Participants were asked, “How often do you eat breakfast?” but there was no definition of what that means, exactly.
What’s more likely: reported skipping breakfast was a marker for a lifestyle and environment that may have predisposed these people to a higher risk of CVD death or that skipping breakfast itself causes CVD death?
Go ahead and skip all the breakfasts you want. And please forward this to the next 10 people who tell you it’s unhealthy to do so.
I am happy to report that I survived the incident and am not concerned at all that my longevity has been compromised.
My 2013 summary of eggs, dietary cholesterol and heart disease (see here) is still valid and I highly recommend patients and readers read that post plus my updates on eggs with newer data (see here and here) rather than information related to the new egg study.
Although CNN and other news outlets lead with an inflammatory headline suggesting that eating those 3 eggs increased my risk of heart disease the new egg study could not possibly prove causation because it was an observational study.
Nutritional epidemiology has come under considerable criticism in the last few years for churning out these weak observational studies .John Ionaddis has been particularly vocal about these limitations, writing:
A large majority of human nutrition research uses nonrandomized observational designs, but this has led to little reliable progress. This is mostly due to many epistemologic problems, the most important of which are as follows: difficulty detecting small (or even tiny) effect sizes reliably for nutritional risk factors and nutrition-related interventions; difficulty properly accounting for massive confounding among many nutrients, clinical outcomes, and other variables; difficulty measuring diet accurately; and suboptimal research reporting. Tiny effect sizes and massive confounding are largely unfixable problems that narrowly confine the scenarios in which nonrandomized observational research is useful
This egg study contains the usual flaws that render it inconclusive:
First, the study relies on data collected from a food frequency questionnaire. Have you ever sat down and tried to recall exactly what you ate in the previous week? How accurate do you think your estimate of specific food items would be?
Ed Archer has written about the inaccuracy of the food frequency questionairres extensively. Here’s a sample from one of his devastating critiques;
In lieu of measuring actual dietary intake, epidemiologists collected millions of unverified verbal and textual reports of memories of perceptions of dietary intake. Given that actual dietary intake and reported memories of perceptions of intake are not in the same ontological category, epidemiologists committed the logical fallacy of “Misplaced Concreteness.” This error was exacerbated when the anecdotal (self-reported) data were impermissibly transformed (i.e., pseudo-quantified) into proxy-estimates of nutrient and caloric consumption via the assignment of “reference” values from databases of questionable validity and comprehensiveness. These errors were further compounded when statistical analyses of diet-disease relations were performed using the pseudo-quantified anecdotal data. These fatal measurement, analytic, and inferential flaws were obscured when epidemiologists failed to cite decades of research demonstrating that the proxy-estimates they created were often physiologically implausible (i.e., meaningless) and had no verifiable quantitative relation to the actual nutrient or caloric consumption of participants.
In addition to unreliable initial data the subjects were followed up to 30 years without any update on their food consumption. Has your food consumption remained constant over the last 30 years? Mine hasn’t. I went from avoiding eggs to eating them ad lib and without concern for my cardiovascular health about 5 years ago after looking at the science related to dietary cholesterol.
It’s Hard To Get Around Confounding Variables
Observational studies like this one try to take into account as many factors as they can which might influence outcomes. Invariably, however, there are factors which are unaccounted for, indeed unknowable, which could be influencing the results.
Individuals who were avidly trying to follow a healthy lifestyle in 1985 likely had drummed into their heads the message when these questionnaires were filled out that they needed to limit egg consumption. These individuals were also likely following other healthy habits, including exercising more, smoking less, and eating more fruits and vegetables and less junk food.
Observational studies cannot account for all these confounding variables.
At science-media centre.org they do a fantastic job of having independent experts in the field present their evaluation of scientific studies which have been popularized in the media. For the JAMA egg study their analyses can be found here.
Prof Kevin McConway, Emeritus Professor of Applied Statistics, The Open University emphasized the problem with residual confounding :
That’s because, for instance, there will be many other differences between people that eat many eggs and people that eat few other than their egg consumption. These other differences might be what’s causing higher death rates in people who eat a lot of eggs, rather than anything to do with the eggs themselves. The researchers point out that this has been a particular problem in some previous studies, and that this may have been a reason for inconsistency in the results of those studies. They have made considerable efforts to allow statistically for other differences in the new study. But they, correctly, point out that their own study is still not immune from this problem (known as residual confounding), and that therefore it’s impossible to conclude from this new study that eating eggs, or consuming more cholesterol in the diet, is the cause of the differences in cardiovascular disease rates and overall death rates that they observed.
For observational epidemiological studies like this egg study which show increased risks that are only “modest” it is highly likely that the next such study will find something different.
Eggs Are Not Eaten In Isolation
Finally, It’s important to remember that eggs, like most foods, are rarely consumed without accompanying food. This accompaniment is often bacon in the US. Eggs are often cooked in oil or butter and unless you cook them yourself you are unlikely to know the nature of the oil.
Eggs are frequently components of recipes.
We have no idea how these factors play into the results of the egg study.
So, rather than drastically cutting egg consumption I propose that there be a drastic cut in the production of weak observational nutrition studies and a moratorium on inflammatory media coverage of meaningless nutritional studies.