redOrbit Staff & Wire Reports – Your Universe Online
Red meat has often been flagged as a cardiovascular risk because of its fat and cholesterol content, but a new study published online this week in the journal Nature Medicine has uncovered a lesser known health risk associated with hamburgers and steaks.
That health risk is the compound l-carnitine, which is also a common ingredient in energy drinks. According to researchers from the Cleveland Clinic, bacteria living in the human digestive tract metabolize the compound and change it into trimethylamine-N-oxide (TMAO) — a substance which has previously been linked to atherosclerosis (clogging or hardening of the arteries).
Co-author Stanley Hazen, head of cardiovascular medicine at the Ohio health center, told Chris Woolston of Nature News that a person´s unique set of intestinal microbes could be as important to a person´s health as the dietary information included on nutrition labels.
They can create a vast array of different molecules out of the food that we eat, and those molecules can have a tremendous impact on our metabolic processes, he added. To illustrate that point, Hazen and his colleagues recruited 77 volunteers — 26 of whom were vegetarians or vegans — and gave them l-carnitine as either a supplement or as a natural ingredient in red meat food products.
“Tests showed that consuming l-carnitine increased blood levels of trimethylamine-N-oxide (TMAO), a compound that, evidence suggests, can alter the metabolism of cholesterol and slow the removal of cholesterol that accumulates on arteries’ walls,” Woolston said.
However, even when taking supplements of the compound, vegans and vegetarians produced “far less TMAO than meat eaters,” and fecal studies revealed that “meat eaters and non-meat eaters“¦ had very different types of bacteria in their guts.”
Hazen concluded that eating red meat on a regular basis likely encourages the growth of bacteria that transform l-carnitine into TMAO. To double-check those findings, he and his colleagues tested both the l-carnitine and TMAO levels in the blood of nearly 2,600 individuals who were having elective heart-related check-ups.
Alone, the compound was found to have little impact, but individuals who had a combination of high l-carnitine and TMAO levels were found to be candidates for cardiovascular disease. The findings, Bloomberg´s Elizabeth Lopatto explains, demonstrates that using l-carnitine as a dietary supplement could be risky. Individuals doing so should be studied closely in order to make sure that the bacteria responsible for elevating TMAO levels remain in check.
And for those who love a good steak every now and again, fear not — “the study does not mean that red meat is entirely bad or that it is best to avoid it entirely,” said Gina Kolata of the New York Times.
Hazen explains that meat is a good source of both protein and B vitamins, both of which are “essential for health,” Kolata said. However, it does demonstrate that saturated fat and cholesterol might not be the only risk factors involved in eating beef and other types of red meat.