Ask The Expert About New Red Meat And Heart Disease Research
Is grass-fed, free-range meat healthier than other types of meat? Does carnitine affect vegans differently than non-vegans? How does the human body use carnitine? Dr. Michael Lauer answered these listener questions and more about the latest research on red meat and heart disease. Dr. Lauer is the director of the Division of Cardiovascular Sciences at the National Heart, Lung, and Blood Institute (NHLBI), part of the National Institutes of Health (NIH). Some questions have been edited for space and clarity.
Q: In what levels is L-carnitine present in other meat (aside from red) and dairy products, in comparison to the levels in red meat? – from Juliana via Facebook
A: Carnitine is found in much higher levels in red meat than in other foods. In 100g of red meat, there are 95 mg of carnitine; in 100g of chicken breast there are 3.9 mg of carnitine. In 100 ml of whole milk, there are 3.7 mg of carnitine. In contrast, in 100g of a green vegetable like asparagus there are only 0.2 mg of carnitine.
Q: Since bacteria in fish create TMA, how would fish fit into the dietary picture? – from Stephen via Facebook
A: This is a fascinating question. Some marine animals, in particular sharks and deeper sea fish have high concentrations of TMAO (the toxic metabolite of TMA) in their tissues. In sharks, TMAO counteracts the toxic effects of urea (a break-down product of protein). In other fish, TMAO counteracts the effects of high water pressure, pressure which would otherwise crush cells.
What are the implications for the dietary picture? We honestly don’t know. Dr. Stanley Hazen’s [a guest on the program] work suggests that TMAO generated through dietary carnitine and gut bacterial activity worsens an individual’s cholesterol profile and exacerbates blood vessel disease. We don’t know whether dietary fish TMAO is harmful.
Q: Is there a difference between eating grass-fed, free-range red meat vs. other types of red meat? – from kforselius via Web
A: Some people think so, though the evidence is not definitive. It has been argued that grass-fed, free-range red meat is leaner, with less fat. We don’t know whether we can reduce the risk of heart attack or stroke by substituting “standard” meat with grass-fed, free-range meat. It’s a hypothesis that would be worth testing.
Q: What about leaner red meats such as elk, buffalo and venison? – from Chris via Facebook
A: Same answer as above.
Q: What is carnitine used for by the body? – from Andrew via Facebook
A: We can think of carnitine as a “fuel injector.” It enables mitochondria, the “fuel cells” of the body, to take up fat; with the aid of carnitine, mitochondria can absorb fat and burn it for energy.
Q: What about the genotypes of people who eat red meat? There are markers for cardiovascular disease, were they looked at? Humans have been eating red meat for a long time. – from Marjorie via email