Steer clear of steak. A new study suggests that how gut microbes decompose red meat increases the risk of heart disease.
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Our guts are awash in bacteria, and now a new study fingers as culprits in heart disease. A complex dance between microbes and a component of red meat could help explain how food can lead to atherosclerosis. The work also has implications for some energy drinks and energy supplements, which contain the same nutrients as these bacteria like chasing.
Red meat is considered bad news regarding heart health, although studies are not compatible how can hurt and if it always does. In addition, it is unclear which components of meat are bad. Various studies have examined the fat or saturated sodium, but the results are inconsistent and sometimes depend on whether the meat has been processed or not. Stanley Hazen, section chief of preventive cardiology and biochemist at the Cleveland Clinic in Ohio, questions whether another ingredient could be harmful: L-carnitine, a nutrient that helps transport fatty acids into energy plants the cell mitochondria. L-carnitine is a popular additive to energy drinks and supplements that claim to boost energy levels. In food, the highest levels of L-carnitine in red meat.
Hazen focus on L-carnitine was something of a wild guess based on the earlier work he had done. There are two years, he and his colleagues published a paper in Nature identifying a compound in the blood called trimethylamine N -oxide (TMAO). It seemed to correlate with future heart disease risk and cause heart disease when fed to mice. TMAO is created when intestinal bacteria decompose certain compounds in food. Hazen wondered if bugs can also convert L-carnitine OTMA, which, in turn, could put the heart at risk.
To find out, Hazen, his PhD student Robert Koeth, and colleagues bought a George Foreman grill and started cooking steaks. "People lined up for the study," says Hazen, and participants "tend to be young, hungry students." Blood tests administered after revealed level rise OTMA. This showed that something was the conversion of L-carnitine to TMAO, but researchers could not say yet that the culprits were bacteria. To pin it down, they gave five of antibiotics broad spectrum volunteers for a week to remove microbes from the gut, and then repeated the experiment. This time, there was virtually no TMAO in the blood or urine after the volunteers ate a steak, suggesting the conversion could not be done without the bacteria.
"When you measure things in people's blood, you do not think of [them] as from bacteria," says Hazen, but in this case appears to be what is happening. The situation is the latest in a series of studies that have shown that the population of bacteria in our intestines, collectively known as the microbiome of the gut-can influence everything from weight loss to brain chemistry.
as the researchers now describe in Nature Medicine , mice fed a diet supplemented with L-carnitine for 15 weeks had significantly higher levels of TMAO than control animals. animals obtain additional L carnitine had roughly twice the burden of atherosclerosis in arteries compared to mice a normal diet.
And the intestines of mice get additional L-carnitine also adapted, becoming enriched for various classes of bacteria that could more easily convert L-carnitine OTMA. This suggested that people who eat lots of red meat may be particularly effective for converting L-carnitine to TMAO and that the consumption of food in moderation might be less damaging because the conversion could be slower. Twenty-three vegans and vegetarians given L-carnitine supplements were, Hazen's group found, less able to synthesize TMAO than those who regularly eat red meat.
It is still unclear why TMAO seems to promote atherosclerosis. Hazen group work by suggesting that TMAO seems to make it easier for the immune cells in the arteries to accumulate cholesterol. Another mystery is how other foods containing L-carnitine could have an impact TMAO levels. For example, the fish, which is thought to reduce cardiovascular risk, also contains much lower levels of L-carnitine, as chicken and milk, says Dariush Mozaffarian, an epidemiologist at the Harvard School of Public Health in Boston, who has studied meat and heart disease, in an email. Inconsistencies also remain about how red meat is really dangerous. That said, although more work needs to be done to unravel the connection L-carnitine-microbe in people, "these results may prove seminal in the field," writes Mozaffarian.
"It tells a very compelling story, "says Daniel Rader, a preventive cardiologist at the University of Pennsylvania. The best way to determine exactly how L-carnitine affects cardiovascular disease, he said, is a clinical trial that manipulates the amount of L-carnitine people take in. Whether a trial such as this is feasible, however, this study "at least would suggest well, even if you have checked your LDL [cholesterol]" with drugs, "eating red meat could still be bad for you. "
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