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Conventional common wisdom has been that red meat consumption increases the risk of developing heart disease. There are a lot of studies indicating this may be true, but there are also a lot of studies indicating this may not.

A report from the Harvard Health Blog last year discussed this. Not only is there disagreement over what (in red meat) would be the cause, various other foods recognized as healthy also contain significant quantities of the same substances which often take the blame. And in the case of processed red meat (which is unequivocally a negative factor for heart health), the clear connection appears to have more to do with the high salt-content of processed red meats than any naturally occurring substance in the meats itself.

So, is there any modern science which takes into account the likely decrease of other healthier foods in diets with high red meat consumption when evaluating its risk to heart health? As we know, proportion and quantity play just as large a role in the effects of what we eat as what they are made of. For instance, vitamin E and other antioxidants (things which are very healthy) are known to actually promote cancer when over-consumed. Given the conflicting evidence on red meat's role in encouraging heart disease, it seems possible that the real culprit is actually the total diet rather than some specific poison.

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    Not sure I understand. Is the question whether there is modern science that 1) assesses heart disease risk AND distinguishes between 2a) consumption of red meat vs 2b) non-consumption of other, healthier foods as the source? How would one construct an experiment to address that? How do you have someone eat red meat without giving up some other component of the diet? Or give up red meat without replacing the calories with another source? Over a long enough period of time? Without the confounding variable of the potential health benefit of overall calorie reduction?
    – Tom Barron
    Commented Mar 1, 2014 at 17:12
  • To answer this negatively, someone would have to look at every scientific study that has ever been written about the relationship between red meat and heart disease and establish that this specific question has never been addressed. I doubt any of us has the time or energy to carry out such a comprehensive survey. However, I think it likely that the question has not been addressed because if so, someone would have answered positively by now.
    – Tom Barron
    Commented Mar 1, 2014 at 17:16
  • @TomBarron 1) There's a difference between differentiating an increase in quantity A from a decrease in quantity B and being pedantic. It's easy to examine groups that consume otherwise identical diets save identical quantities of different test substances (e.g. red meat, fish, potatoes, tofu). There's using meta-studies to look for a statistically significant difference between the observed health effects of diets lacking nutritional content and common diet profiles which are high in meat. And, that's just to name a few. 2) You could say the same about any question asking if evidence exists.
    – CircleSquared
    Commented Mar 8, 2014 at 7:57
  • I'm actually more interested in this: "vitamin E and other antioxidants (things which are very healthy) are known to actually promote cancer when over-consumed." Do you have some sources for that?
    – user11643
    Commented Jun 10, 2014 at 21:36

4 Answers 4

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Question: Does red meat increase the risk of heart disease?

My answer: Consumption of red meat was associated with increased risk of heart disease in some, but not all, studies, which suggests that some common red meat ingredient, like sodium or other preservatives, rather than red meat by itself may be the actual risk factor.

http://circheartfailure.ahajournals.org/content/7/4/552.long A prospective study in Swedish men, 2014

...processed red meat consumption, but not unprocessed red meat, is associated with an increased risk of heart failure.

In above study, the suggested, but not yet proven, risk factors in processed meat included preservatives: sodium, nitrites and phosphates.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2803089/ Meat intake and mortality: a prospective study of over half a million people, 2009

Red and processed meat intakes were associated with modest increases in cardiovascular disease mortality.

In some studies, red meat was not associated with heart disease:

http://www.nel.gov/vault/2440/web/files/DietaryPatterns/DPRptFullFinal.pdf Systematic review, 2014

Evidence of a relationship...characterized by red and processed meat...and an increased risk of cardiovascular disease is limited and less consistent.

http://www.ncbi.nlm.nih.gov/pubmed/19364995 Systematic review, 2009

Insufficient evidence of association is present for intake of...saturated and polyunsaturated fatty acids...meat, eggs and milk [and the risk of coronary heart disesae].

http://www.ncbi.nlm.nih.gov/pubmed/22333876 A prospective study in Japan, 2012

Moderate meat consumption, up to ~100 g/day, was not associated with increased mortality from ischemic heart disease, stroke or total cardiovascular disease among either gender

Also, saturated fat (usually high in red meat) may not be associated with heart disease

http://annals.org/article.aspx?articleid=1846638&resultClick=3 Systematic review, 2014

Current evidence does not clearly support cardiovascular guidelines that encourage...low consumption of total saturated fats.

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Yes, it does increase the risk for chronic diseases including cardiovascular diseases.

Red meat consumption is associated with an increased risk of total, cardiovascular disease, and cancer mortality. Substitution of other healthy protein sources for red meat is associated with a lower mortality risk.

Source: Pan A, Sun Q, Bernstein AM, Schulze MB, Manson JE, Stampfer MJ, Willett WC, Hu FB. Red meat consumption and mortality: results from 2 prospective cohort studies. Arch Intern Med. 2012 Apr 9;172(7):555-63. doi: 10.1001/archinternmed.2011.2287. Epub 2012 Mar 12.

High consumption of red meat and processed meat has been associated with increased risk of several chronic diseases. ... In a dose-response meta-analysis, consumption of processed meat and total red meat, but not unprocessed red meat, was statistically significantly positively associated with all-cause mortality in a nonlinear fashion. These results indicate that high consumption of red meat, especially processed meat, may increase all-cause mortality.

Source: Larsson SC, Orsini N. Red meat and processed meat consumption and all-cause mortality: a meta-analysis. Am J Epidemiol. 2014 Feb 1;179(3):282-9. doi: 10.1093/aje/kwt261. Epub 2013 Oct 22.

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    You know. Those studies must take care about what they call "red meat". Lean cuts of red meat are far healthier than a fatty cut, for example. I'm really wary about studies that overgeneralizes "red meat" to encompass any part of the animal and don't distinguish between different cuts.
    – T. Sar
    Commented May 11, 2015 at 12:07
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    In a dose-response meta-analysis, consumption of processed meat and total red meat, but not UNPROCESSED red meat, was statistically significantly positively associated with all-cause mortality in a nonlinear fashion. You answered your own question with that citation, processing is what is harmful in that study.
    – Richard Stanzak
    Commented Jan 24, 2017 at 18:39
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More recent studies confirm the correlation between red meat and TMAO, and between TMAO and heart disease, as mentioned in @tst's answer.

…

Trimethylamine N-oxide (TMAO) is a dietary byproduct that is formed by gut bacteria during digestion. The chemical is derived in part from nutrients that are abundant in red meat. High saturated fat levels in red meat have long been known to contribute to heart disease, the leading cause of death in the United States. A growing number of studies have identified TMAO as another culprit.

…

When on the red meat diet, the participants consumed roughly the equivalent of 8 ounces of steak daily, or two quarter-pound beef patties. After one month on this diet, blood levels of TMAO were three times higher than when participants were on the diets based on either white meat or non-meat protein sources.

Half of the participants were also placed on high-saturated fat versions of the three diets. The diets all had equal amounts of calories. The researchers found that saturated fat had no additional effect on TMAO levels.

…

— Eating red meat daily triples heart disease-related chemical | National Institutes of Health (NIH)

This was based on Impact of chronic dietary red meat, white meat, or non-meat protein on trimethylamine N-oxide metabolism and renal excretion in healthy men and women | European Heart Journal, Volume 40, Issue 7, 14 February 2019, Pages 583–594 | Oxford Academic.

An earlier study establishes the link between TMAO and heart disease:

Conclusions

Data presented in this study showed a significant positive dose-dependent association between plasma TMAO levels, cardiovascular events, and mortality. Additional meta-analyses based on individual participant data will be required to characterize the shape of these dose-response associations, to characterize the nature of this association in populations with different dietary environments, and to explore the usefulness of TMAO plasma levels in prediction of risk of CVD. Future prospective studies will also be needed to determine whether the modulation of TMAO levels or its precursors might represent a novel potential therapeutic approach to change CVD prognosis.

— Gut microbe-generated metabolite trimethylamine-N-oxide as cardiovascular risk biomarker: a systematic review and dose-response meta-analysis | European Heart Journal, Volume 38, Issue 39, 14 October 2017, Pages 2948–2956 | Oxford Academic.

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Apparently the link between heart disease and red meat is found. It is L-carnitine. In short, there are gut bacteria that "eat" L-carnitine and produce a substance called TMAO, which causes atherosclerosis. For more information check this page or just google "L-carnitine TMAO

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    Here's a quote from that link: “This new research was well-done and compelling, but it’s too early to decide that this molecule, TMAO, causes atherosclerosis in humans or that this is responsible for some of the associations of meat intake and risk.”
    – Oddthinking ♦
    Commented Oct 29, 2014 at 5:34
  • I think it's pretty convincing findings. But you are correct, it is not conclusive. So the vote down is fair enough.
    – tst
    Commented Oct 31, 2014 at 11:10

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