The skeptical cardiologist wrote a post extolling the virtues of egg nog back in 2013.
Today I’m reposting it and wishing all my readers and patients a great Christmas and a fantastic 2019.
It’s Christmas Eve and you are starting to make merry. Time to break out the egg nog? Or should you eschew this fascinating combination of eggs, dairy and (often) alcohol due to concerns about heart disease?
Could this be related to excessive consumption of egg nog?
Egg nog is composed of eggs, cream, milk and booze. All of these ingredients have become associated with increased risk of heart disease in the mind of the public.
Nutritional guidelines advise us to limit egg consumption, especially the yolk, and use low-fat dairy to reduce our risk of heart disease
A close look at the science, however, suggests that egg nog may actually lower your risk of heart disease.
Eggs are high in cholesterol but as I’ve discussed in a previous post, cholesterol in the diet is not a major determinant of cholesterol in the blood and eggs have not been shown to increase heart disease risk.
Full fat dairy contains saturated fat, the fat that nutritional guidelines tell us increases bad cholesterol in the blood and increases risk of heart attacks. But some saturated fats improve your cholesterol profile and organic (grass-fed, see my previous post) milk contains significant amounts of omega-3 fatty acids which are felt to be protective from heart disease.
Milk and dairy products are associated with a lower risk of vascular disease!
Whether you mix rum, brandy, or whisky into your egg nog or you drink a glass of wine on the side you are probably lowering your chances of a heart attack compared to your abstemious relatives. Moderate alcohol consumption of any kind is associated with a lower risk of dying from cardiovascular disease compared to no alcohol consumption.
So, drink your egg nog without guilt this Holiday Season!
You’re actually engaging in heart healthy behavior.
The skeptical cardiologist pointed out in 2013 that there was no good evidence supporting limiting dietary cholesterol to 300 mg per day. I exulted, therefore, in 2016 , when this long-standing dietary recommendation came out of the US dietary guidelines.
Investigators randomized 128 patients with prediabetes or type 2 diabetes (T2D) to a high egg or a low egg diet.
Throughout all study phases, including the 3-mo weight-loss phase, participants consuming the high-egg diet were instructed to eat 2 eggs/d at breakfast for 6 d/wk (12 eggs/wk). Those in the low-egg group were directed to consume <2 eggs/wk, and to match the protein intake that the high-egg group had consumed at breakfast with 10 g lean animal protein (meat, chicken, or sh) or other protein-rich alternatives, such as legumes and reduced-fat dairy products (also consumed at breakfast). Recommended egg-cooking methods were boiled or poached, but they could also be fried if a polyunsaturated cooking oil, such as olive oil, was used. The prescribed diets were energy and macronutrient matched, as reported previously
At the end of 12 months both groups had lost about 3 kg in weight.
The investigators measured everything they could to look at diabetic and cardiometabolic biomarkers which might suggest adverse effects of egg eating on the cardiovascular system but they could find no difference between the egg eaters and the non egg eaters.
High egg consumption had no adverse effects on the following factors that are felt to be important in the development of atherosclerosis:
-measures of systemic and vascular inflammation [high sensitivity C-reactive protein (hs-CRP), IL-6, soluble E-selectin (sE-selectin)],
-oxidative stress (F2-isoprostanes), the adipokine adiponectin (which also modulates insulin resistance), and
-glycemia [fasting plasma glucose, glycated hemoglobin (HbA1c), and a medium-term measure of glycemia, 1,5-anhydroglucitol (1,5AG)].
The authors suggested that nutritional guidelines stop worrying about limiting eggs.
Article Two: Half A Million Chinese Can’t Be Wrong
This observational study published in Heart found that egg consumption in a huge Chinese population was associated with less stroke, and major cardiac events (MCE):
Compared with non-consumers, daily egg consumption was associated with lower risk of CVD (HR 0.89, 95% CI 0.87 to 0.92). Corresponding multivariate-adjusted HRs (95% CI) for IHD, MCE, haemorrhagic stroke and ischaemic stroke were 0.88 (0.84 to 0.93), 0.86 (0.76 to 0.97), 0.74 (0.67 to 0.82) and 0.90 (0.85 to 0.95), respectively. There were significant dose-response relationships of egg consumption with morbidity of all CVD endpoints (P for linear trend <0.05). Daily consumers also had an 18% lower risk of CVD death and a 28% lower risk of haemorrhagic stroke death compared to non-consumers.
The lower risk for stroke and cardiovascular death in egg eaters persisted after accounting for known CVD risk factors.
(And yes, I agree this is an observational study which we should take with huge grains of salt and pepper).
Are EGG Whites The Skim Milk Scam of The Egg Industry?
I’ve written about the scam that is skim milk but it occurs to me that egg white consumption is equally nonsensical.
What happens to the wonderfully nutritious yolk of the egg when it is brutally separated from its white? It is put in a container and sold as liquid egg yolk. Makers of mayonnaise are big consumers of liquid egg yolk.
Thus, like dairy farmers who double their sales by selling skim milk and its dairy fat separately, egg producers are probably delighted that Americans are consuming egg whites , allowing them to get two products from a single egg.
As I wrote previously: not everyone is an egg lover and I’m fine with that. There is no evidence that you have to eat them. You could feel towards them as did Alfred Hitchcock :
“I’m frightened of eggs, worse than frightened, they revolt me. That white round thing without any holes … have you ever seen anything more revolting than an egg yolk breaking and spilling its yellow liquid? Blood is jolly, red. But egg yolk is yellow, revolting. I’ve never tasted it.”
For those that don’t find yellow revolting, however, avoiding egg yolk makes no nutritional sense.
The skeptical cardiologist and his Eternal Fiancee’ have escaped dreary and oceanopenic St. Louis and are spending a week in allegedly sunny and definitely beachy San Diego.
Upon arrival we took in a Farmer’s Market in Little Italy and stumbled into Ironside Fish and Oyster.
Always in search of heart-healthy, unique and local fish dishes, I spotted on the menu a luncheon special of sheepshead fish.
California sheepshead (Semicossyphuspulcher), the existence of which I was previously unaware, turned out to be a fascinating and most delicious fish.
Before I could order it, I had to verify that I wasn’t contributing to the extinction of a species. The IUCN Red List of Threatened species lists the CS as “vulnerable” because:
“The natural history of this species, including its limited geographic range along inshore habitat, the likely increasing interest in the fishery and the currently unsustainable fishing levels (according to the models of Alonzo et al. 2004), together with the difficulties in enforcing existing regulations strongly suggest that this species will continue to decline if stronger protective action is not put into place. “
After learning the CS was vulnerable, I had to make a critical decision: should I eat it before it disappeared, robbing me of a chance to ever taste it, or should I order something that wasn’t vulnerable, thus contributing to the preservation of the continuing biodiversity of the planet. I elected to taste it.
Gender Fluid Fish
Further research revealed that the CS transitions from a reproductively functional female at birth, to a functional male during the course of a lifespan in response to social factors (?reverse Bruce Jenner).
In some sequentially hermaphroditic fish species, animals develop first as male and then switch to female (a condition called protandry), and in others, the individuals develop first as female and then switch to male (protogyny).
Clownfish (as in Finding Nemo) do the opposite of the sheepshead and are protandrous:
This species lives within sea anemones in groups of two large fish and many small fish. The two large fish are the only sexually mature fish and are a male and female breeding pair. All of the smaller fish are male. If the large breeding female is removed, her male mate changes sex to female and the next largest fish in the group rapidly increases in size and takes over the role as the sexually mature male.
While waiting for the vulnerable and sequentially hermaphroditic sheepshead to arrive, I sampled an equally
stupendous and heart-healthy side of cannelloni bean cassoulet. Chock full of Mediterranean diet essentials including kale, beans and mustard seeds, it worked really well as an appetizer.
Do not make the mistake of looking at this youtube video while waiting for your sheepshead entree’ as I did. The disturbing human-like teeth will not be part of your meal.
Finally, the 4 ounces of CS arrived, perfectly prepared a la plancha,
with an accompanying lemon butter sauce that was divine. Although butter is not officially a big part of the Mediterranean diet, frequent readers of the skepcard know that dairy fat does not make you fat or promote heart disease, and is fine (in moderation of course) as part of a heart-healthy diet.
Speaking of lingering bad dietary advice, if you investigate the nutritional content of sheepshead at a site like SELF Nutrition, the old canard that we should be limiting our dietary cholesterol raises its ugly head. Because sheepshead contain significant amounts of cholesterol (presumably from carnivorously munching on shellfish with its scary human-like choppers), the misguided nutritionists at SELF Nutrition and other would-be nutritionistas pronounce it as not optimally healthy.
PS. If you’d really like to get your nerd on about sequential hermaphroditism check out this graphic showing the independent evolution of this feature across different phylogenetic lineages!
The 2015-2020 Dietary Guidelines for Americans (DGA) have finally been released and I’m sure that most of you could care less what they say. You may think that they can’t be trusted because you believe the original science-based recommendations have been altered by political, food and agribusiness forces. Perhaps you don’t trust science to guide us in food choices. Perhaps, like the skeptical cardiologist, you realize that the DGA has created, in the past, more problems than they have corrected.
This time, the skeptical cardiologist believes they have made a few strides forward, but suffer from an ongoing need to continue to vilify all saturated fats.
As such, the DGA no longer lists a recommended limit on daily cholesterol consumption (step forward) but persists in a recommendation to switch from full fat to non fat or low fat dairy products, which is totally unsubstantiated by science, (see my multiple posts on this topic here).
By now you should have gotten the message that a healthy diet consists of lots of fruits, vegetables, nuts, legumes, fish, olive oil and whole grains. The DGA emphasizes this.
There is general consensus that processed foods and added sugar should be limited.
Most of the controversy is about what to limit and how much to limit foods that are considered unhealthy.
Red meat and processed meat remain in the crosshairs of the DGA (although not stated explicitly), but eggs and cholesterol have gotten a pass, something which represents a significant change for the DGA and which I have strongly advocated (here and here).
But hold on, my professional organization, the American College of Cardiology says otherwise.
Misleading Information From the American College of Cardiology
The American College of Cardiology sent me an email and posted on their website the following horribly misleading title:
The first paragraph of the ACC post reads as follows:
“Physiological and structural functions of the body do not require additional intake of dietary cholesterol according to the 2015 Dietary Guidelines released on Jan. 7 by the U.S. Departments of Health and Human Services (HHS) and of Agriculture (USDA). As such, people should practice healthy eating patterns consuming as little dietary cholesterol as possible. – ”
While technically these statements can be found in the document (by digging way down) the executive summary (infographic below) says nothing about limiting cholesterol.
The “Key Recommendations” list eggs as included under a “healthy eating pattern” along with other protein foods.
In addition, there is no mention of cholesterol under what a healthy pattern limits.
In the same section on cholesterol that the ACC inexplicably has chosen to emphasize, is this sentence:
“More research is needed regarding the dose-response relationship between dietary cholesterol and blood cholesterol levels. Adequate evidence is not available for a quantitative limit for dietary cholesterol specific to the Dietary Guidelines.”
So the DGA recommends no specific limit on dietary cholesterol.
This is consistent with what the DG advisory committee recommended when they wrote “dietary cholesterol is no longer a nutrient of concern.”
The DGA goes on to state:
“A few foods, notably egg yolks and some shellfish, are higher in dietary cholesterol but not saturated fats. Eggs and shellfish can be consumed along with a variety of other choices within and across the subgroup recommendations of the protein foods group.”
The Vegan Agenda
I have a theory on why the ACC went so wildly astray in reporting this information: they are led by a vegan.
The current president of the ACC, Kim Williams, is an evangelical vegan, unrepentant, as this NY times article points out. Apparently, he tries to convert all his patients to the “plant-based diet.”
He is quoted extensively in the ACC blurb on the DGA and is clearly attempting to put a bizarre vegan spin on the new guidelines, ignoring the evidence and the progressive shift from the 2010 guidelines.
Can any information from the ACC be trusted if such basic and important science reporting was so heavily distorted by its President?
No wonder Americans tune out dietary advice: it can so easily be manipulated by those with an agenda.
Eggs (and dietary cholesterol) should no longer be restricted in a heart-healthy diet as the skeptical cardiologist has pointed out here.
But if we’re eating eggs should they come from “pasture-raised” (or grass-fed or pastured) hens?
The arguments for choosing hens that can roam freely and eat bugs, clover, and grass from the ground beneath them are of four types:
1. Ethical. The vast majority of eggs come from hens that are kept in a small cage most of their life and are never allowed to see the light of day or engage in their normal activities. This is inhumane.
2. Esthetic. Eggs from pasture-raised hens (PRH) taste better.
3. Health. PRH eggs are more nutritious because of the better food ingested by PRH and the manner in which they live and are treated.
4. Environmental. PRH operations are more sustainable and contribute less toxins and antibiotics to the environment.
PETA gives a horrific description of what factory farm hens endure here. Here’s an excerpt:
“hens are shoved into tiny wire “battery” cages, which measure roughly 18 by 20 inches and hold up to 10 hens, each of whom has a wingspan of 32 inches. Even in the best-case scenario, each hen will spend the rest of her life crowded in a space about the size of a file drawer with four other hens, unable to lift even a single wing.
The birds are crammed so closely together that these normally clean animals are forced to urinate and defecate on one another. The stench of ammonia and feces hangs heavy in the air, and disease runs rampant in the filthy, cramped sheds. Many birds die, and survivors are often forced to live with their dead and dying cagemates, who are sometimes left to rot.”
PETA and vegans advocate not eating any animals or animal products. They have an inherent bias against omnivorous diets and their interpretation of the nutritional science always reflects that.
I sympathize with the plight of factory farms hens, but it is very difficult to martial scientific arguments in the area of the ethical treatment of animals.
A brief Google search yields dozens of websites which proclaim that PRH eggs are far more nutritious and better for you than conventional eggs. When a source for this claim is listed it comes from one of two studies:
1. Mother Earth News (Oct/Nov 2007). Mother Earth News is not known for its scientific rigor, but they did publish an analysis of the nutritional content of eggs from 14 farms with PRH and compared it to what the USDA had published for the nutritional content of conventional eggs.
Let me just say that this “study” would never be published in a reputable scientific journal due to flaws in the study design. For one thing, the PRH eggs should have been compared to conventional eggs analyzed at the same time in the same way in a blinded fashion. Also, there is no statistical analysis of the data.
Here is how Mother Earth News summarizes their findings:
These amazing results come from 14 flocks around the country that range freely on pasture or are housed in moveable pens that are rotated frequently to maximize access to fresh pasture and protect the birds from predators. We had six eggs from each of the 14 pastured flocks tested by an accredited laboratory in Portland, Oregon.
PRH eggs compared to the conventional eggs had
• 1/3 less cholesterol • 1/4 less saturated fat • 2/3 more vitamin A • 2 times more omega-3 fatty acids • 3 times more vitamin E • 7 times more beta carotene
Eggs were vilified during the heyday of the anti-fat movement because of their cholesterol and saturated fat content. We now know that neither one of these macronutrients causes heart disease; so the fact that PRH eggs have less of them is irrelevant. In addition, no other study has replicated the findings with respect to cholesterol and saturated fat content.
The higher levels of Vitamin A, Vitamin E and beta-carotene make sense given the differing food intake of PRH compared to factory hens, but again, there is nothing to suggest Americans aren’t consuming plenty of these vitamins in other foods. In addition, studies looking at supplementing diet with Vitamin E and beta-carotene have shown no overall health or cardiovascular benefits.
This study is a legitimate peer-reviewed scientific study published in a reputable scientific journal by researchers who did not have any obvious bias or conflict of interest.. Bias can run both ways in these types of studies, as any research supported by the conventional egg industry would receive pressure to find no difference between conventional and PRH eggs. However, studies funded by advocates of PRH eggs would be hoping to find significant benefits of their eggs.
The 2010 study found:
“Compared to eggs of the caged hens, pastured hens’ eggs had twice as much vitamin E and long-chain omega-3 fats, 2.5-fold more total omega-3 fatty acids, and less than half the ratio of omega-6:omega-3 fatty acids (P<0.0001).”
Of the nutrient differences reported between PRH and conventional eggs the omega-3 differences are the most intriguing. Both of these studies found a doubling of omega-3 fatty acids in PRH eggs, which are generally considered the healthiest of all fatty acids. The second study found a lower ratio of omega-6:omega-3 in the PRH eggs. The relative benefits of omega-6 and omega-3 fatty acids in the diet is a topic of considerable controversy in the scientific literature right now but, in general, recommended diets like the Mediterranean feature higher omega-3 to omega-6 ratios than standard Western diets.
There are no studies looking at the differing effects of consuming PRH versus conventional eggs on biomarkers or outcomes in humans.
Thus, we have no idea whether the overall package of nutrients delivered in the PRH eggs would improve blood pressure, cholesterol parameters or markers of inflammation or whether they could lower your risk of heart attack or stroke.
I have been eating PRH eggs whenever possible for the last few years and I swear they taste better than conventional eggs. In preparation for this post, I had decided that a blinded tasting of eggs would be needed to support my totally subjective assessment of PRH egg superiority.
However, it turns out that several blinded tasting egg comparison have already been done and the results are quite shocking to me.
The Food Lab at Serious Eats (which, by the way is dedicated to “unraveling the mysteries of home cooking through science”) had 8 tasters taste scrambled eggs prepared from PRH eggs, conventional hen eggs and various omega-3 supplemented eggs
One half of the tasters found no difference in taste between the various kinds of eggs, but those who did favor an egg favored the PRH eggs and the higher omega-3 eggs. The yolks of the PRH eggs and omega-3 eggs were more on the “intensely orange” end of the spectrum.
Did the more orange yolks taste better or were the tasters biased by the more intense color?
The tasting was repeated, this time with the color of the eggs masked by adding green food coloring. In this color-blind tasting:
“most people could not taste any difference in the eggs. Those who did taste a difference picked a totally different batch of eggs—this time, there was no clear winner, and no discernible trends based on how the eggs were produced or levels of omega-3’s”
A food writer for the Washington Post did a similar taste test, this time with actual blind folds, and although she was convinced that the eggs from her backyard hens would be superior, a panel of six tasters could find no difference between hers, conventional eggs, and organic eggs.
Although these taste tests haven’t been published in peer-reviewed scientific journals, they are likely as close as we are going to get to the truth. The fact that the organizers of the tests were biased towards PRH eggs tasting better but found no difference means almost certainly, alas, that there is no taste superiority for PRH eggs.
Are PRH Eggs Worth The Extra Cost?
Ultimately, this is a question for each individual. True PRH eggs cost upwards of 5 dollars per dozen compared to around 2$ per dozen (prior to the recent avian flu outbreak).
It is hard to justify that cost based on nutritional, health or taste considerations as I’ve shown.
My oldest daughter, Chelsea Pearson, has, along with thousands of other city dwellers, begun raising chickens in her backyard. In addition to collecting delicious eggs from the hens, she has become attached to them and finds them to be interesting and enjoyable pets.
After weighing the ethical and environmental concerns despite the absence of conclusive health benefits or taste superiority I have elected to continue paying a premium for PRH eggs.
I have the financial resources to justify this decision but for those without such resources I totally understand a decision to eat conventional eggs.
A year ago one of my patients began experiencing chest pain when he walked up hills. Subsequent evaluation revealed that atherosclerotic plaque (95% narrowing of a major coronary artery ) was severely reducing the blood flow to his heart muscle and was the cause of his chest pain. When this blockage was opened up with a stent he no longer had the pain.
Along with other medications (aspirin and plavix to keep his stent open) I had him start atorvastatin, the generic version of Lipitor, a powerful statin drug that has been shown to prevent progression of atherosclerotic plaque and thereby reduce subsequent heart attacks, strokes and death in patients like him
I saw him in the office the other day in follow up and he was feeling great . He asked me “Doc I read your post yesterday.s Since you say that cholesterol in the diet doesn’t matter anymore, does that mean I don’t have to take my cholesterol drug anymore.?”
His question gets at the heart of the “diet-heart hypothesis”. The concept that dietary modification, with reduction of cholesterol and fat consumption can reduce coronary heart disease.
The science supporting this hypothesis has never been strong but the concept was foisted on the American public and was widely believed. It was accepted I would say because it has a beautiful simplicity which can be summarized as follows:
“If you eat cholesterol and fat it will enter your blood stream and raise cholesterol levels. This excess cholesterol will then deposit in your arteries, creating fatty plaque , clogging them and leading to a heart attack.”
This concept was really easy to grasp and simplified the public health recommendations.
However, cholesterol blood levels are determined more by cholesterol synthesized in the liver and predicting how dietary modifications will effect these levels is not easy.
Since the public has had the diet-heart hypothesis fed to them for decades and given its beautiful simplicity it is hard to reverse this dogma. My patient’s question reflects a natural concern that if science/doctors got this crucial question so wrong, is everything we know about cholesterol treatment and heart disease wrong?
In other words, are doctors promoting a great cholesterol hoax?
Evidence Strongly Supports Statins in Secondary Prevention
For my patient the science supporting taking a cholesterol-lowering statin drug is very solid. There are multiple excellent studies showing that in patients with established coronary artery disease taking a statin drug substantially reduces their risk of heart attack and dying.
These studies are the kind that provide the most robust proof: randomized, prospective and blinded.
When cardiologists rate the strength of evidence for a certain treatment (as done for lifestyle intervention here) we use a system that categorizes the evidence as Level A, B, or C quality.
LeveleA quality (or strong) evidence consists of multiple,large, well-done, randomized trials such as exist for statins in patients with coronary heart disease.
Level B Evidence comes from a single randomized trial or nonrandomized studies.
Level C evidence is the weakest and comes from “consensus opinion of experts, case studies or standard of care.”
When treatment recommendations are based on Level C evidence they are often reversed as more solid data is obtained. Level A recommendations almost always hold up over time.
The level of evidence supporting restricting dietary cholesterol and fat to reduce heart attacks and strokes has always been at or below Level C and now it is clear that it is insufficient and should be taken out of guideline recommendations.
Evidence Strongly Supports Atherogenic Cholesterol is Related to Coronary Heart Disease
There are other lines of evidence that strongly support the concept that LDL cholesterol (bad cholesterol) or an atherogenic form of LDL cholesterol is strongly related to the development of atherosclerosis. If you are born with really high levels you are at very high risk for coronary heart disease, conversely if you are born with mutations that cause extremely low levels you are highly unlikely to get coronary heart disease.
Thus, the cholesterol hypothesis as it relates to heart disease is very much till intact although the diet-heart hypothesis is not.
Conflating the Diet-Heart Hypothesis and the Cholesterol Hypothesis
There is an abundance of misinformation on the internet that tries to conflate these two concepts. Sites with titles like “The Great Cholesterol Lie” , “The” Cholesterol Hoax”, The Cholesterol Scam” abound .
These sites proclaim that cholesterol is a vital component of cell membranes (it is) and that any attempt by diet or drugs to lower levels will result in severe side effects with no benefit
Doctors, according to these types of sites, in collusion with Big Pharma, have inflated the benefits of statin drugs and overlooked the side effects in the name of profit. Often, a “natural” alternative to statins is promoted. In all cases a book is promoted.
The Great Cholesterol Truths
It’s unfortunate that nutritional guidelines have promoted restriction of cholesterol and fat for so long. These guidelines (like most of nutritional science) were based on flawed observational studies. They should not have been made public policy without more consensus from the scientific community. The good news is that ultimately the truth prevails when enough good scientific studies are done.
It is right to question the flimsy foundation of nutritional recommendations on diet and heart disease but the evidence for statin benefits in patients with established coronary heart disease is rock solid.
Hopefully, the less long-winded explanation I provided my patient in the office will persuade him to keep on taking his atorvastatin pills while simultaneously allowing him to eat eggs, shrimp and full fat dairy without guilt.
I think eggs are wonderful. They are little balls of nutrition that can be prepared in numerous fascinating ways to make breakfast interesting and delicious. I particularly like omelets. Alas, when I was training as a medical student the medical establishment had embraced the diet-heart hypothesis. It was felt that dietary cholesterol and fat (subsequently modified to saturated fat) by increasing levels of cholesterol in the blood (subsequently modified to raising levels of bad or LDL cholesterol) were responsible for the increasing rate of coronary heart disease that was being observed.
This certainly made sense at the time: If you eat too much cholesterol, of course it’s going to raise your blood cholesterol levels and contribute to the buildup of those nasty cholesterol plaques that would clog your arteries and give you heart attacks and strokes.
Since egg yolks contain 210 mg of cholesterol on average (more recent data suggest they only contain 184 mg/egg), eggs became a target of the dietary police.
The American Heart Association (AHA, the same organization that until recently endorsed sugar-laden cereals like Cocoa Puffs as “heart healthy”) had decided decades ago to recommend restricting egg consumption. In 2010, AHA guidelines restricted everybody’s total cholesterol to <300 mg per day on the flimsiest of evidence. From the AHA guidelines:
“Although there is no precise basis for selecting a target level for dietary cholesterol intake for all individuals, the AHA recommends <300 mg/d on average. By limiting cholesterol intake from foods with a high content of animal fats, individuals can also meet the dietary guidelines for saturated fat intake. This target can be readily achieved, even with periodic consumption of eggs and shellfish. As is the case with saturated fat intake, reduction in cholesterol intake to much lower levels (<200 mg/d, requiring restriction of all dietary sources of cholesterol) is advised for individuals with elevated LDL cholesterol levels, diabetes, and/or cardiovascular disease.”
The official US dietary guidelines on the topic of dietary cholesterol read as follows
“the body uses cholesterol for physiological and structural functions, but it makes more than enough for these purposes. Therefore, people do not need to eat sources of dietary cholesterol. Cholesterol is found only in animal foods. The major sources of cholesterol in the American diet include eggs and egg mixed dishes (25% of total cholesterol intake), chicken and chicken mixed dishes (12%), beef and beef mixed dishes (6%), and all types of beef burgers (5%). Cholesterol intake can be reduced by limiting the consumption of the specific foods that are high in cholesterol. Many of these major sources include foods that can be purchased or prepared in ways that limit the intake of cholesterol (e.g., using egg substitutes). Cholesterol intake by men averages about 350 mg per day, which exceeds the recommended level of less than 300 mg per day. Average cholesterol intake by women is 240 mg per day.
Dietary cholesterol has been shown to raise blood LDL cholesterol levels in some individuals. However, this effect is reduced when saturated fatty acid intake is low, and the potential negative effects of dietary cho- lesterol are relatively small compared to those of saturated and trans fatty acids. Moderate evidence shows a relationship between higher intake of cholesterol and higher risk of cardiovascular disease. Independent of other dietary factors, evidence suggests that one egg (i.e., egg yolk) per day does not result in increased blood cholesterol levels, nor does it increase the risk of cardiovascular disease in healthy people. Consuming less than 300 mg per day of cholesterol can help maintain normal blood cholesterol levels. Consuming less than 200 mg per day can further help individuals at high risk of cardiovascular disease.”
Americans were being told to severely restrict their egg consumption, especially if they had high cholesterol levels, diabetes, or heart disease. Even one egg a day seemed too much. As a cardiologist in training I dutifully took these recommendations to heart. I can’t tell you how many egg beater or egg white omelets I cooked over the next 25 years.
As more evidence accumulated, however, the bulk of the scientific evidence was coming down clearly on the side of eggs and the lack of effect of dietary cholesterol on blood cholesterol levels. As The Skeptical Cardiologist I began embracing the heresy of eating eggs, yolk and all, about two years ago.
Several large epidemiological studies have examined the association of egg consumption and serum cholesterol. The Framingham Heart Study examined the serum cholesterol in high versus low egg consumption and found no significant difference in either men or women. The association between self-reported dietary intake of eggs and serum cholesterol was examined in a population of 12,000 men in the Multiple Risk Factor Intervention Trial. Paradoxically, the men who consumed more eggs had lower serum cholesterol than those who consumed fewer eggs.In the Third National Health and Nutrition Examination Survey (NHANES III), the diets of 20,000 participants were evaluated.
“Compared to egg consumers, nonconsumers had higher rates of inadequate intake (defined by Estimated Average Requirements (EAR) or < 70% Recommended Dietary Allowance (RDA)) for vitamin B12 (10% vs. 21%), vitamin A (16% vs. 21%), vitamin E (14% vs. 22%) and vitamin C (15% vs. 20%). After adjusting for demographic (age, gender and ethnicity) and lifestyle variables (smoking and physical activity), dietary cholesterol was not related to serum cholesterol concentration. People who reported eating > or = 4 eggs/wk had a significantly lower mean serum cholesterol concentration than those who reported eating < or = 1 egg/wk (193 mg/dL vs. 197 mg/dL, p < 0.01”
Study after study in the next 20 years showed that egg consumption was not associated with coronary heart disease and strokes. A more recent study from Spain shows no association of egg consumption on cardiovascular disease. A meta-analysis of all prospective cohort studies published in 2013 concluded that there was no association between higher egg consumption and coronary heart disease or stroke. Studies (randomized controlled trials) that actually prove that egg consumption causes cardiovascular disease are totally lacking. Nutritional guidelines should have concluded that there was no reason to restrict egg consumption in the vast majority of Americans.
Unfortunately, the AHA guidelines (and mainstream nutritional advisors) to this day continue to embrace the 300 mg/ day limit on cholesterol (although most other countries have dropped it). Most of my patients, having heard that eggs are bad for the heart, mistakenly try to restrict the amount they eat or eat egg whites. I see my fellow doctors in the doctors’ lounge taking boiled eggs out of the refrigerator, scooping the yolk out and eating only the egg white.
Why doesn’t more cholesterol in the diet lead to higher blood cholesterol level and subsequently to heart attacks? The answer is complicated, beyond the scope of this blog, but it illustrates how amazingly complex the body’s regulation of lipids and lipoproteins is, as well as how complicated the process of atherosclerosis is.
There are at a very basic level 3 main types of fat that doctors measure in the blood to help us gauge heart disease risk: the low density lipoprotein (LDL) cholesterol portion or “bad”, the high-density lipoprotein (HDL) cholesterol or “good,” and the triglycerides (esterified fatty acids). On a very simplistic level, we tell patients that higher LDL levels tend to build up fatty plaques, whereas higher HDL levels can be thought of as reducing fatty plaques. When we eat an egg there is a complex reaction to the fats, proteins, sugar, and cholesterol absorbed into the blood stream. Although the LDL rises (which might increase coronary artery disease (CAD) risk), the HDL also rises (which might lower CAD risk) and there is a variable response of triglycerides. To further complicate things, each of the cholesterol fractions has good forms and bad forms. LDL can be in a large, “fluffy” state that is not prone to promoting plaque formation or a small, dense form that does promote plaque formation. Eggs seem to promote the less atherogenic forms of both LDL and HDL. In addition, inflammation plays an important role in the process of atherosclerosis. Certain components of egg yolks may actually reduce inflammation, making plaque formation less likely.
Certain components of eggs may be beneficial and outweigh any theoretical concern about cholesterol consumption.. Eggs are the major sources of lutein and zeaxanthin, two potent anti-oxidants, which in addition to their recognized protective effects against macular degeneration and cataract formation, may also reduce LDL oxidation.
Eggs also contain choline, a nutrient that is needed for membrane formation, methylation and acetylcholine biosynthesis, which plays a major role in normal fetal development. Some studies suggest a role of choline in protecting against Alzheimer’s disease
Eating eggs may contribute to weight loss compared to eating carbohydrates. A recent study compared two different breakfasts, a bagel-based and an egg-based breakfast. During the egg period, men had a significantly lower caloric intake not only in the next meal, but also in the following 24 hours.
To make things more complicated, all eggs are not created equal. Hens that are allowed to range freely on a farm and eat grass, bugs and what might be considered their normal diet, have a different amount of omega-3 fatty acids than those that are fed grain. Given America’s current obsession with fish oil supplements (see my prior post), this makes these eggs perceived as healthier. By manipulating the diet of hens, even those stuck in cages, the omega-3 content of eggs can be increased. Is this healthier?
The limit on dietary cholesterol of 300 mg imposed by the AHA and the USDA in their guidelines, unnecessarily has my patients worrying about cholesterol in all the things that they eat. For example, there is a lot of cholesterol in shellfish. There is no evidence that eating shellfish is bad for the heart or your cholesterol profile. For example, this recent study showed no effect of eating cold water prawns on plasma cholesterol or lipoproteins.
The Bottom Line:
Eggs are an affordable (15 cents/egg) source of high quality protein and fat. Although they contain a lot of cholesterol, there is no evidence (with the possible exception of diabetics) that egg consumption is related to risk of coronary heart disease; they may in fact reduce the risk of stroke.
Since this new evidence has emerged, I regularly enjoy the deliciousness of a three egg omelet with cheese and other ingredients without guilt and I encourage my patients to do the same. Personally, especially in my home kitchen, I try to eat eggs that come from hens that are raised under more natural and humane circumstances as I view them as healthier than eggs from factory farms.
Not everyone is an egg lover and I’m fine with that. There is no evidence that you have to eat them. You could feel towards them as did Alfred Hitchcock :
“I’m frightened of eggs, worse than frightened, they revolt me. That white round thing without any holes … have you ever seen anything more revolting than an egg yolk breaking and spilling its yellow liquid? Blood is jolly, red. But egg yolk is yellow, revolting. I’ve never tasted it.”