Another Red Meat Consumption Study

[gleem]

TL;DR

This latest study find that previous studies regarding the negative health effects of consuming red meat are not good enough to recommend how much an individual should consume or use to evaluate personal health risks.

This latest study has raised a storm of protests by health and nutritional experts and organizations. This study reviewed previous studies linking the consumption of red meat to the increase in risks for cardiovascular diseases, cancer. Their conclusion is that the data is not good enough to predict how one should modify or make recommendations on ones consumption of red meat .

In each study, the scientists concluded that the links between eating red meat and disease and death were small, and the quality of the evidence was low to very low.

That is not to say that those links don’t exist. But they are mostly in studies that observe groups of people, a weak form of evidence. Even then, the health effects of red meat consumption are detectable only in the largest groups, the team concluded, and an individual cannot conclude that he or she will be better off not eating red meat.

Called into question is the method by which nutritional studies have been conducted. Select a population and determine their nutritional behavior by questionnaire and follow them for some extended period of time and monitor their health. There is no practical way to conduct a controlled double blind study which is the standard for most other medical studies. Except one was actually done. And the results are interesting.

In the late 60's early 70's Ivan Frantz a physician/professor at the University of Minnesota did a controlled double blind study using institutionalized individuals whose diet could be strictly controlled. The study was to determine the health risk of saturated fats. Ivan Frantz had always be interested in this subject to the extent that he even performed regular blood lipid/cholesterol monitoring of his children. The result of his study did not show any significant difference in life expectancy between a regular saturated fat diet and his low saturated fat diet although those on the low saturated fat diet had lower cholesterol. Note that the saturated fats were replace by vegetable oil. He tried reanalyzing it to no avail and because of the equivocal results he did not publish it until 15 years later but the conclusions stated were guarded so to speak and the study received little attention. Not too long ago another researcher was interested in the health effects of polyunsaturated fats, vegetable oil the recommended replacement for animal fats. This study noted the significant increase in the intake of Linoleic acid an Omega-6 fatty acid the main component of vegetable oil. This study in conjunction with Frantz's study determined there was not health benefit from vegetable oil. You can read a transcript of an interview of Dr. Frantz's son about his fathers work here

So what are we to think about this new study?

Perhaps there is no way to make policies that can be conveyed to the public and simultaneously communicate the breadth of scientific evidence concerning diet.

Or maybe, said Dr. Bier, policymakers should try something more straightforward: “When you don’t have the highest-quality evidence, the correct conclusion is ‘maybe.’”

 

[nsaspook]

The latest study sounds like good science being savaged by "science deniers".

 

[jim mcnamara]

This is the actual article in the Annals of Medicine,American College of Medicine, a good Journal:
https://annals.org/aim/fullarticle/...mption-dietary-guideline-recommendations-from
You should decide on your own whether the meta-study has any merit. I do not agree with @nsaspook 's assessment.

 

[Ygggdrasil]

Here is a critique of the guidelines and meta analyses from the Harvard School of Public Health: https://www.hsph.harvard.edu/nutritionsource/2019/09/30/flawed-guidelines-red-processed-meat/

I'm not sure why the OP highlights the Minnesota Coronary Experiment as one of the only randomized controlled trials (RCTs) on the subject. The authors of the guidelines published a meta-analysis in which they identified 12 RCTs relevant to the question of whether red or processed meats affect health. The Minnesota experiment was not among the 12 RCTs analyzed. Of these, only two reported on the measures they were interested in (cardiovascular mortality, cancer incidence, and diabetes). The two studies that met the analysis criteria were the Lyon Diet Heart Study and the Women's Health Initiative Study on low fat diets. The Lyon study tested the effect of a Mediterranean diet on cardiovascular health while the WHI study looked at the effects of a low fat diet on cardiovascular health. The Lyon study specifically aimed to replace red meat consumption with chicken and fish (along with other alterations to diet), and achieved an average decrease of 1.9 servings of red meat per week among participants. The WHI study merely aimed to lower fat consumption, which resulted in an average decrease of 1.4 servings of red meat per week among participants (along with other changes to diet). While the Lyon study seemed to show greater positive health effects from the dietary change, they largely ignored the results of this trial in favor of the WHI trial because of the difference in sample size (~600 participants for the Lyon trial vs ~49,000 participants for the WHI trial).

Personally, I agree somewhat with both the critics and the authors of the new guidelines. I do think the evidence is somewhat weak for the association between red meat consumption and cancer and even if true, the effects are also very small (the strength of evidence and effect size between the linkage between processed meats and cancer, however, seems stronger from the studies I've looked at, however). Personally, over the past few years I have made an effort to reduce the amount of red meat and processed meat in my diet to maybe at most 2 servings of beef per week and less than one serving of processed meat per week (e.g. I used to eat maybe one hamburger per week. Now, I will typically choose a turkey burger or chicken sandwich instead). This choice is also informed by fact that beef has a much greater environmental impact than other types of meat like pork, chicken and fish.

 

[StoneTemplePython]

Sir David Spiegelhalter is my preferred observer on these sorts of things, as a savvy, non-partisan Bayesian statistician specializing in health risk at Cambridge

This rigorous, even ruthless, review does not find good evidence of important health benefits from reducing meat consumption. In fact, it does not find any good evidence at all.

https://www.bbc.com/news/health-49877237
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This echoes many other studies that have had replication problems in shaky domains (typically social psychology) -- i.e. the purported previously 'discovered effect' is at best weak.

I trust that Spiegelhalter will be on an upcoming epsiode of 'More or Less' since he is one of their favorite boffins

 

[gleem]

You should decide on your own whether the meta-study has any merit

As well as all the other studies on this subject.

It is well known that studies that have negative or equivocal results tend not to get published. Take for example the one I discussed above. The researcher set out believing that there was a connection between life expectancy and consumption of saturated fats only to find out that his data did not support the assumption and withheld publication for 15 years.

I'm not sure why the OP highlights the Minnesota Coronary Experiment as one of the only randomized controlled trials (RCTs) on the subject.

I highlighted it because it was a true controlled study using 9000 confined subjects. Their diet was controlled by the researcher not just specified by a researcher. The object was to determine the health effect of saturated fats not just red meat. As I noted it received little attention when published so I am not surprised it was not reviewed even though it could be used to support their recommendation. I would like to believe the conclusions of qualified researchers but I am not convinced that the assumption inherent this type of research are always valid. Assumptions not only regarding the assessment of equivalence of population but also unrecognized confounding processes. The corrections or adjustments in the data for identified factors for example like age, social status, or protocol compliance carry uncertainties and can vary from population to population. I have wondered if all these corrections overwhelm the statistical nature of the resulting data so that two studies that should produce the same results show differences beyond the calculated statistical level of significance.

From the article of discussion:

Observational studies will continue to be limited by challenges of accurate measurement of diet, the precise and accurate measurement of known confounders (50), and the likelihood of residual confounding after adjusted analyses (13, 14, 16).

I hedge my bets a little too. I eat more chicken and fish than I might otherwise and have replaced some beef with pork. I avoid refined sugar but enjoy regular pasta and artisan white bread especially sourdough despite the warning about refined grain products. I control my caloric intake.

 

[Laroxe]

Most of the dietary advice we receive is based on large epidemiological studies, which trawl data for associations, using such data in meta analysis is a classic example of attempting to make a strong chain out of weak links. Like it or not, this sort of advice is heavily influenced by value systems and vested interests. The promotion of the Mediterranean diet, a fantasy diet created by the researchers, virtually destroyed much of the dairy industry and despite no real evidence it is useful for anything, its still promoted.

I think there is a real problem in that meat consumption is now being included in climate action, again based on flawed research. The claim is that beef production involves greater CO2 release than crops, which is true, however if the measure used was in calorific value the difference is minimal. I believe Germany is already planning to introduce a specific tax on red meat. I suspect this is an issue that won't go away, with the science acting as a side show.