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.
Since the skeptical cardiologist has in previous posts waxed poetic on Jambon Iberico and beef brisket, I feel compelled to comment on this report.
We’ve been through this before and this announcement is not based on any new and striking data.
It is based on reviewing a lot of observational studies from the past decades. It is very important to understand that observational studies do not establish cause and effect, they only look at associations.
GaryTaubes has written eloquently on this in 2012:
“It’s this compliance effect that makes these observational studies the equivalent of conventional wisdom-confirmation machines. Our public health authorities were doling out pretty much the same dietary advice in the 1970s and 1980s, when these observational studies were starting up, as they are now. The conventional health-conscious wisdom of the era had it that we should eat less fat and saturated fat, and so less red meat, which also was supposed to cause colon cancer, less processed meat (those damn nitrates) and more fruits and vegetables and whole grains, etc. And so the people who are studied in the cohorts could be divided into two groups: those who complied with this advice — the Girl Scouts, as Avorn put it — and those who didn’t.
Now when we’re looking at the subjects who avoided red meat and processed meat and comparing them to the subjects who ate them in quantity, we can think of it as effectively comparing the Girl Scouts to the non-Girl Scouts, the compliers to the conventional wisdom to the non-compliers. And the compliance effect tells us right there that we should see an association — that the Girl Scouts should appear to be healthier. Significantly healthier. Actually they should be even healthier than Willet et al. are now reporting, which suggests that there’s something else working against them (not eating enough red meat?). In other words, the people who avoided red meat and processed meats were the ones who fundamentally cared about their health and had the energy (and maybe the health) to act on it. And the people who ate a lot of red meat and processed meat in the 1980s and 1990s were the ones who didn’t.
Here’s another way to look at it: let’s say we wanted to identify markers of people who were too poor or too ignorant to behave in a health conscious manner in the 1980s and 1990s or just didn’t, if you’ll pardon the scatological terminology, give a sh*t. Well, we might look at people who continued to eat a lot of bacon and red meat after Time magazine ran this cover image in 1984 — “Cholesterol, and now the bad news”. I’m going to use myself as an example here, realizing it’s always dangerous and I’m probably an extreme case. But I lived in LA in the 1990s where health conscious behavior was and is the norm, and I’d bet that I didn’t have more than half a dozen servings of bacon or more than two steaks a year through the 1990s. It was all skinless chicken breasts and fish and way too much pasta and cereal (oatmeal or some other non-fat grain) and thousands upon thousands of egg whites without the yolks. Because that’s what I thought was healthy.
So when we compare people who ate a lot of meat and processed meat in this period to those who were effectively vegetarians, we’re comparing people who are inherently incomparable. We’re comparing health conscious compliers to non-compliers; people who cared about their health and had the income and energy to do something about it and people who didn’t. And the compliers will almost always appear to be healthier in these cohorts because of the compliance effect if nothing else. No amount of “correcting” for BMI and blood pressure, smoking status, etc. can correct for this compliance effect, which is the product of all these health conscious behaviors that can’t be measured, or just haven’t been measured. “
For more discussion on the weakness of observational epidemiology upon which this WHO pronouncement rests see here
Even if we were to accept the concept that red meat is a carcinogen, this does not mean everyone should end red meat consumption.
For perspective I would suggest reading this post from cancer researchUK. Although the WHO classifies both smoking and processed red meat as carcinogens they are not in the same ball park in terms of overall cancers and deaths caused as this infographic demonstrates.
A one pack a day cigarette smoker has 20 times the risk of developing small cell lung cancer as a non-smoker.
A high frequency meat eater, on the other hand has a 1.17 time increased risk as the lowest frequency meat eater.
As cancerUK put it:
“We know that, out of every 1000 people in the UK, about 61 will develop bowel cancer at some point in their lives. Those who eat the lowest amount of processed meat are likely to have a lower lifetime risk than the rest of the population (about 56 cases per 1000 low meat-eaters).
If this is correct, the WCRF’s analysis suggests that, among 1000 people who eat the most processed meat, you’d expect 66 to develop bowel cancer at some point in their lives – 10 more than the group who eat the least processed meat.”
So keep in mind
Weak associations between red meat and processed red meat and cancer or heart disease do not establish that one causes the other. Such studies are good for generating hypotheses that then need to be tested.
If processed meats are a carcinogen they are a far, far less important one than cigarette smoking.
NB.From the press release:
“Red meat refers to all types of mammalian muscle meat, such as beef, veal, pork, lamb, mutton, horse, and goat.
Processed meat refers to meat that has been transformed through salting, curing, fermentation, smoking, or other processes to enhance flavour or improve preservation. Most processed meats contain pork or beef, but processed meats may also contain other red meats, poultry, offal, or meat by-products such as blood.
Examples of processed meat include hot dogs (frankfurters), ham, sausages, corned beef, and biltong or beef jerky as well as canned meat and meat-based preparations and sauces.
A summary of the final evaluations is available online in The Lancet Oncology, and the detailed assessments will be published as Volume 114 of the IARC Monographs.”
The skeptical cardiologist participated in the Pedaler’s Jamboree this Memorial Day weekend. This is an annual bicycling/music festival centered around a 30 mile bike ride from Columbia to Boonville, MO along the KT trail as it tracks the Missouri River. It ends at Kemper Park in Boonville with a concert and campout (the highlight of which for me was SHEL)
At various stops along the way we were treated to excellent roots/blues/folk
music. Our favorite moment was listening to an awesome duo from Fort Wayne, Indiana, the White Trash Blues Revival, in a downpour at the McBaine stop. The lead singer/guitarist played a home-made lap steel (made from a skate board and a Red Stripe beer bottle) and the drummer played trash cans, a beer keg and a cardboard box with outstanding results.
During the day, I observed thousands of my fellow pedalers consuming hot dogs and bratwursts at the various stops. In America, during Memorial Day weekend, several million brats and dogs will be consumed which made me ponder: is this increasing Americans’ risk of dying from heart disease?
US dietary-guidelines recommend “eating less” red and processed meat. For cardiovascular disease, these recommendations are based largely on expected effects on blood cholesterol of saturated fat and dietary cholesterol in meats. However, multiple recent published analyses have found no relationships of meat intake with cardiometabolic disease outcomes, including coronary heart disease (CHD), stroke, and diabetes.
This is a really important fact to know when making food choices, so I’m going to highlight it and repeat it:
Scientific studies do not show an association between unprocessed red meat consumption and cardiovascular disease.
“Red meat” is usually defined as unprocessed meat from beef, hamburgers, lamb, pork, or game, and excludes poultry, fish, or eggs.
“Processed meat” is any meat preserved by smoking, curing or salting, or addition of chemical preservatives, such as bacon, salami, sausages, hot dogs, or processed deli or luncheon meats, excluding fish or eggs.
A 2010 meta-analysis of American studies on this showed no increased risk of coronary heart disease for the highest consumers of unprocessed meat versus the lowest.
On the other hand, each serving per day of processed meat was associated with a 42% higher risk of coronary heart disease. Restricted to US studies, each serving per day was associated with 53% higher risk of diabetes.
A recent European study of 448,000 people found no association between unprocessed red meat consumption and mortality. For processed meats, there was an 18% higher risk of death per 50 gm/day serving.
Scientists really don’t know what it is about processed red meat that makes it associated with higher mortality.
As the table below indicates, the amount of saturated fat and cholesterol is not higher, so that does not appear to be the cause.
Because sodium nitrite is used to cure most processed meats, processed meats have about 4 times the amount of sodium as red meats.
High dietary sodium intake significantly increases blood pressure. Habitual consumption may also worsen arterial compliance and promote vascular stiffness, so It’s possible this is a factor.
Nitrate and nitrite levels are about 40% higher in processed meats and this has been suggested as a contributor to higher CVD and cancer rates.
However, 80-95% of dietary nitrates come from vegetables sources and a very significant source of nitrites is the breakdown of nitrates to nitrites by bacteria in saliva. Recent studies suggest that the blood pressure lowering effect of vegetables may be mediated by their nitrate content.
At present, it seems that dietary nitrite and nitrate have cardiovascular protective effects. … the effects of nitrite and nitrate to enhance NO bioavailability, to improve endothelial function, to cause vasodilation, and to inhibit platelet aggregation may at least partly mediate their cardiovascular beneficial effects. … Taking the data presented above together with the failure of recent studies to show significant correlation between nitrite and nitrate exposure and cancer, we suggest that the benefits of dietary nitrite and nitrate will strongly outweigh any potential risks, particularly for cardiovascular disease patients.
So, there is a signal from observational data that processed meats may increase cardiovascular disease and death, but exactly which ones might be the culprits and how this might work is entirely unclear. I’m still consuming brats, sausages, and hot dogs on occasion. Riding a bike, listening to music and drinking beer is a fine occasion for that.
I would advise the following
Don’t worry about nitrates/nitrites in processed meats. Science has not determined whether this is good or bad for you. Brands of bacon/sausage that claim no nitrates/nitrites are often using “natural” forms of nitrates that come from sources such as celery powder or sea salt.
Processed meats contain a lot of salt. Your body likely senses that and cuts back on salt consumption in other food choices during the day, especially if you indulge moderately. If you eat too much, too often, you put yourself at risk for high blood pressure and its attendant consequences. What is “too much” is uncertain, but the higher rates of heart disease and death don’t really seem to kick in until you eat the equivalent of greater than 80 grams per day.
Personally, I choose sustainably, humanely, “naturally” and locally raised processed meats whenever possible but there is no evidence-based medicine supporting this choice.