Longevity

Longevity Briefs: Why Is Red Meat Linked With Heart Disease? The Answer Could Lie In Our Guts

Posted on 8 August 2022

Longevity briefs provides a short summary of novel research in biology, medicine, or biotechnology that caught the attention of our researchers in Oxford, due to its potential to improve our health, wellbeing, and longevity.

Why is this research important: Numerous studies have linked red meat consumption to cardiovascular disease, but the strength of this relationship has been a controversial subject, and we don’t really understand the underlying mechanisms behind it. This subject is particularly relevant to older people, as they are more at risk of cardiovascular disease, but also stand to benefit more from the intake of high protein foods (as they can help to offset age-related muscle loss.) One theory is that it isn’t so much the compounds contained within red meat, but rather the way the bacteria in our guts process them that is responsible for the increased risk of heart disease.

What did the researchers do: This study, which was conducted in the United states, looked at almost 4000 men and women over the age of 65. Participants reported their consumption of different animal-sourced foods, and researchers regularly measured the blood levels of a group of chemicals called trimethylamine N-oxide (TMAO) related metabolites. TMAO is produced in the liver from trimethylamine (TMA), which is itself produced by gut bacteria when they process L-carnitine, choline and lecithin, compounds found meat, eggs and dairy products (with L-carnitine being particularly abundant in red meat). Participants were followed up for a median of 12.5 years, and the development of atherosclerosis – the progressive narrowing of the arteries due to the build-up of fatty plaque – was recorded.

How TMAO is thought to contribute to atherosclerosis. Trimethylamine is produced by gut bacteria and converted into trimethylamine N-oxide in the liver. This promotes inflammation, which is a key driver of atherosclerosis and most other diseases of ageing. Though eggs, poultry and fish also contribute to TMAO production, they were not found to be associated with increased risk of atherosclerosis in this study.
Source

Key takeaway(s) from this research: Higher consumption of red meat, but not poultry, eggs or fish, was associated with increased risk of atherosclerosis – about 22% increased risk per serving per day. Of the total increase in risk, about 10% of that excess risk was estimated to be due to TMAO-related metabolites. High blood sugar, high insulin (the hormone that controls blood sugar), and high levels of C-reactive protein (a marker for inflammation) also appeared to play a role in the relationship between red meat consumption and disease risk. However, high blood pressure and cholesterol levels did not appear to play a significant role.

This is not to say that having high blood pressure or cholesterol doesn’t increase your risk of cardiovascular disease – that much is well established. Rather, the study is suggesting that red meat doesn’t increase your risk of heart disease by raising your cholesterol or blood pressure, but rather by raising the levels of certain compounds produced by gut bacteria when red meat is digested, and by promoting inflammation.


References

Dietary Meat, Trimethylamine N-Oxide-Related Metabolites, and Incident Cardiovascular Disease Among Older Adults: The Cardiovascular Health Study: https://doi.org/10.1161/ATVBAHA.121.316533

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