Gut Bacteria and Red Meat Nutrient Linked to Heart Disease
Medical researchers from the Cleveland Clinic’s Center for Cardiovascular Diagnostics & Prevention have determined that L-carnitine – a compound found in red meat, many energy drinks and supplements – accelerates heart disease. The interesting part is that red meat alters intestinal bacteria, causing them to produce a lethal artery-clogging chemical.
The research, published in the Journal Nature Medicine, follows decades of research linking red meat consumption to heart disease and atherosclerosis.
Researchers conducting past research connecting heart disease with red meat have pointed to the fat and cholesterol content in red meat as the central culprit. While most experts agree that saturated fat and meat’s cholesterol content is still a likely component, this new research from the Cleveland Clinic is a game-changer.
The researchers conducted a series of studies using both humans and animals. In the human research, circulating levels of L-carnitine were tested among 2,595 patients who underwent evaluation for heart conditions. The researchers found that higher levels of L-carnitine were significantly associated with greater degrees of cardiovascular disease, and more specifically, atherosclerosis – the hardening of the arteries due to increased plaque and artery damage.
The researchers also tested and tracked the consumption of red meat and L-carnitine specifically through the digestive tract, and found that red meat eaters maintained a particular type of bacteria species that converted L-carnitine – a nutrient high in red meat, certain energy drinks and some supplements – into trimethylamine-N-oxide (TMAO).
The researchers then found that the TMAO produced by the gut bacteria was specifically linked to atherosclerosis.
Furthermore, the researchers found that meat-eaters had greater numbers of these TMAO-producing pathogenic bacteria, and thus metabolized more TMAO than did vegans and vegetarians.
To screen out the different possibilities, the researchers ran a series of additional tests that included giving L-carnitine in supplement form to vegetarians and omnivores, and compared their production of TMAO. They found that the vegetarians did not produce anywhere near the levels of TMAO that the omnivores experienced following L-carnitine supplementation.
The researchers also used antibiotics to remove intestinal bacteria, and repeated the tests. They discovered that the connection was their respective intestinal bacteria. The omnivore diet had promoted some species of bacteria that produce TMAO from L-carnitine.
The research was led by esteemed heart researcher Dr. Stanley Hazen. “The bacteria living in our digestive tracts are dictated by our long-term dietary patterns,” said Dr. Hazen in a statement. “Vegans and vegetarians have a significantly reduced capacity to synthesize TMAO from carnitine, which may explain the cardiovascular health benefits of these diets.”
This is not the first study that has linked “bad” gut bacteria to heart disease. A 2011 study also led by Dr. Hazen determined that TMAO was produced by converting choline – another component typically found with L-carnitine in animal foods. Previous research established both choline and L-carnitine as precursors to TMAO production.
The pathogenic bacteria suspected among meat-eaters include Cytomegalovirus (CMV), Helicobactor, Chlamydia, and Chlamydophila pneumoniae. These pathogenic bacteria utilize a type of enzyme called flavin monooxygenase (FMO).
These bacteria apparently process choline and L-carnitine into TMAO utilizing the FMO enzymes. Dr. Hazen’s researchers found these two TMAO precursors were predominant among eggs, shellfish, fish, red meat, liver and even to some degree, milk.
With regards to taking supplements with L-carnitine, drinking energy drinks or any other source of L-carnitine, Dr. Hazen’s research has established that vegetarians will convert less of this L-carnitine to TMAO than will omnivores, due to the increased pathogenic bacteria counts resulting from a diet rich in animal foods.
Other studies – notably those conducted by Swedish researcher Dr. Gunnar Johansson – have also linked omnivore diets to increased pathogenic bacteria and higher levels of pathogenic enzymes. These enzymes – including beta-glucuronidase, beta-glucosidase, and sulphatase – have been associated with increased rates of colon cancer. Dr. Johansson’s decades-long research has established that these pathogenic bacteria and subsequent enzymes decrease when people reduce their consumption of red meat, or convert from an omnivore diet to a vegetarian diet.
Written by Case Adams, Naturopath
Koeth RA, Wang Z, Levison BS, Buffa JA, Org E, Sheehy BT, Britt EB, Fu X, Wu Y, Li L, Smith JD, Didonato JA, Chen J, Li H, Wu GD, Lewis JD, Warrier M, Brown JM, Krauss RM, Tang WH, Bushman FD, Lusis AJ, Hazen SL. Intestinal microbiota metabolism of l-carnitine, a nutrient in red meat, promotes atherosclerosis. Nat Med. 2013 Apr 7.
Wang Z, Klipfell E, Bennett BJ, Koeth R, Levison BS, Dugar B, Feldstein AE, Britt EB, Fu X, Chung YM, Wu Y, Schauer P, Smith JD, Allayee H, Tang WH, DiDonato JA, Lusis AJ, Hazen SL. Gut flora metabolism of phosphatidylcholine promotes cardiovascular disease. Nature. 2011 Apr 7;472(7341):57-63.
Holmes HC, Burns SP, Michelakakis H, Kordoni V, Bain MD, Chalmers RA, Rafter JE, Iles RA. Choline and L-carnitine as precursors of trimethylamine. Biochem Soc Trans. 1997 Feb;25(1):96S.
Ley RE, Turnbaugh PJ, Klein S, Gordon JI. Microbial ecology: human gut microbes associated with obesity. Nature. 2006;444:1022–1023.
Bidulescu A, Chambless LE, Siega-Riz AM, Zeisel SH, Heiss G. Usual choline and betaine dietary intake and incident coronary heart disease: the Atherosclerosis Risk in Communities (ARIC) study. BMC Cardiovasc Disord. 2007;7:20.
Johansson G, Holmén A, Persson L, Högstedt B, Wassén C, Ottova L, Gustafsson JA. Dietary influence on some proposed risk factors for colon cancer: fecal and urinary mutagenic activity and the activity of some intestinal bacterial enzymes. Cancer Detect Prev. 1997;21(3):258-66.
Johansson GK, Ottova L, Gustafsson JA. Shift from a mixed diet to a lactovegetarian diet: influence on some cancer-associated intestinal bacterial enzyme activities. Nutr Cancer. 1990;14(3-4):239-46.
Johansson G, Holmén A, Persson L, Högstedt R, Wassén C, Ottova L, Gustafsson JA. The effect of a shift from a mixed diet to a lacto-vegetarian diet on human urinary and fecal mutagenic activity. Carcinogene-sis. 1992 Feb;13(2):153-7.
Case Adams is a California Naturopath with a PhD in Natural Health Sciences, and a Board Certified Alternative Medicine Practitioner. He has authored 26 books on natural healing strategies. “My journey into writing about alternative medicine began about 9:30 one evening after I finished with a patient at the clinic I practiced at over a decade ago. I had just spent the last two hours explaining how diet, sleep and other lifestyle choices create health problems and how changes in these, along with certain herbal medicines and other natural strategies can radically yet safely turn our health around. As I drove home that night, I realized this knowledge should be available to more people. So I began writing about health with a mission to reach those who desperately need this information. The strategies in my books and articles are backed by scientific evidence along with wisdom handed down through traditional medicines for thousands of years.”