We have known for decades about heart disease and the effects of red meat and saturated fats being a cause of elevated cholesterol. But we've also known that is not the whole story and now surprising new research is pointing to gut bacteria and the actual chemical that is produced by meat as the culprit for heart disease.
Carnitine is found in red meat and is also used by body builders as a supplement for energy. Researchers have found that in the intestinal tract, bacteria convert carnitine into a metabolite called TMAO and TMAO promotes thickening of the arteries. Steak consumption caused subjects in the study to immediately produce large amounts of TMAO. Vegetarians did not produce the chemical.
Many people who become vegetarian say that they can no longer digest red meat. It turns out that they actually lose the ability to metabolize carnitine over time because they do not develop the gut bacteria that meat eaters have.
How did the researchers know it was the gut bacteria? They gave the study participants large doses of antibiotics to wipe out the normal flora in the intestinal tract and then none of the meat eaters or vegetarians produced TMAO after eating steak or taking carnitine pills.
The researchers from Cleveland Clinic, examined record of 2,595 patients who had undergone cardiac evaluations and found that patients with high levels of TMAO and carnitine were the most likely to develop heart disease, heart attacks, strokes and death within the next three years.
"Cholesterol is still needed to clog the arteries, but TMAO changes how cholesterol is metabolized-like the dimmer on a light switch," said lead author Stanley Hazen. "This may explain why two people can have the same LDL level, but one develops cardiovascular disease and the other doesn't."
It would appear that carnitine alone is not the problem but a regular diet of meat creates the gut bacteria that break carnitine down into TMAO. Vegetarians and meat eaters have very different gut bacteria. TMAO may be a waste product but it is significantly affecting cholesterol metabolism and deposition into arteries.
What should you take from this study?
--The Mediterranean diet is still the most heart healthy diet. (Small amounts of meat and red wine; grains and vegetables in large amounts. Avoid processed foods.)
--Try to eat only organic local farmed meat and chicken. It takes an effort but is worth the time and money to avoid antibiotics, growth hormones and horrible animal conditions.
-- Never take carnitine supplements or energy drinks.
--Small amounts of meat means no more than 4-6 oz. Think about that the next time you think about steak.
This post originally appeared at Everything Health. Toni Brayer, MD, FACP, is an ACP Internist editorial board member who blogs at EverythingHealth, designed to address the rapid changes in science, medicine, health and healing in the 21st Century.