Dr. Stanley Hazen and Dr. W.H. Wilson Tang of the Cleveland Clinic said the chemical byproduct trimethylamine N-oxide -- TMAO -- is produced when intestinal bacteria digest the nutrient phosphatidylcholine, commonly known as lecithin.
To demonstrate the role of gut flora in forming TMAO, human subjects were asked to eat two hard-boiled eggs -- a common dietary source of lecithin -- and a capsule of labeled lecithin as a tracer. After ingestion, TMAO levels in the blood increased, the researchers said.
However, when these same subjects were given a brief course of broad-spectrum antibiotics to suppress their gut flora, their TMAO levels were suppressed, and no additional TMAO was formed, even after ingesting lecithin. These results demonstrated the intestinal bacteria are essential for the formation of TMAO, the study said.
The researchers then measured TMAO levels of 4,000 adults undergoing cardiac evaluation at Cleveland Clinic for three years. They found higher TMAO blood levels were associated with higher future risks of death and non-fatal heart attack or stroke for the ensuing three-year period, independent of other risk factors and blood test results.
"More studies are needed to confirm that TMAO testing might help guide physicians in providing individualized nutritional recommendations for preventing cardiovascular disease," Hazen said in a statement. "Our goal is not to suggest dietary restrictions of entire food groups. Eggs, meat and other animal products are an integral part of most individuals' diets. Our work shows, however, that when digesting these foods, gut flora can generate a chemical mediator, TMAO, that may contribute to cardiovascular disease."