Prevention of heart disease has centered on smoking cessation, controlling blood pressure, achieving an appropriate weight, regular exercise, control of blood sugar, and control of your cholesterol. Despite addressing and controlling these items, individuals still have heart attacks and strokes and vascular events. Researchers are now directing their attention to a dietary metabolite of red meat called trimethlamine N-oxide or TMAO.
Recent peer-reviewed and published studies have shown an association between high blood levels of TMAO and increased risk of all-cause mortality and cardiovascular disease. A 2017 study published in the Journal of the American Heart Association found a 60 percent increased risk of a major cardiovascular event and death from all causes in individuals with elevated TMAO. Other research has linked high TMAO levels to heart failure and chronic kidney disease.
Our bodies make TMAO when choline and L-carnitine are metabolized by our gut bacteria in the microbiome. Red meat is particularly high in L-carnitine. A study group at the Cleveland Clinic found that red meat raised the TMAO levels more than white meats or non-meat protein. They also discovered that red meat allowed more bacteria in the gut microbiome to be switched to producing TMAO. Of interest was the fact that the amount of fat in the food, particularly saturated fat, made no difference on the TMAO levels obtained. Stanley Hazen, MD, PhD, section head of preventive cardiology at the Cleveland Clinic, feels the TMAO pathway is “independent of the saturated fat story.” The important issue to Dr. Hazen is the presence of the gut bacteria to produce the TMAO from foods eaten.
Not all scientists buy into the TMAO theory of cardiovascular disease because of the relatively high level of TMAO found in many fish. Some experts believe the beneficial effects of omega-3 fatty acids in fish offset the negative effects of TMAO. The leading researcher on TMAO says it is an evolving study and he is supported by experts who believe TMAO is “atherogenic, prothrombotic and inflammatory” per Kim Williams, MD, chief of cardiology at Rush University Medical Center in Chicago.
There is even a blood test to measure TMAO levels developed by the Cleveland Clinic and available through Quest Labs. Do not get too excited about asking your physician to order it on your blood because it requires eliminating meat, poultry, and fish plus other food items for several days in advance of the test.
For many years researchers at the Cleveland Clinic and Emory University recognized that 50 percent or more of heart attacks occurred in men who followed all the risk reduction guidelines including stopping smoking, controlling blood pressure and lipids, losing weight and getting active. Perhaps the answer as to why will be in the TMAO research, and the solution will be changing the gut bacteria or their ability to convert L-carnitine to TMAO.
Steven Reznick is an internal medicine physician and can be reached at Boca Raton Concierge Doctor.
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