New Link Found Between Red Meat and Heart Disease: an Intestinal Bacteria

In a new study published April 7 in the journal Nature Medicine, scientists from the Cleveland Clinic reported evidence suggesting that the long-known link between eating red meat and increased risk of heart disease may be explained not just by the cholesterol-inducing fat content of meat, but by a bacteria that red-meat-eating may foster in the gut.

In previous studies, “Consumption of red meat has been found to increase the risk of death from heart disease, even when controlling for levels of fat and cholesterol,” a release issued by Nature, publisher of Nature Medicine, reported.

This and other research led Dr. Stanley Hazen, Head of Cardiovascular Medicine at the Cleveland Clinic in Ohio, and his team to hypothesize that another mechanism besides fat and cholesterol - one involving a chemical-producing bacteria fostered in the gut by eating red meat - may be causing the increased heart risk associated with consuming red meat. To test their hypotheses, they performed the new study.

In the study, published April 7 in the journal Nature Medicine, Dr. Hazen and his colleagues reported that a bacteria apparently found in greater abundance in the intestines of red-meat-eaters appears to feed on the nutrient L-carnitine, contained in red meat. When fed L-carnitine, this bacteria produces a chemical called TMAO which enters the blood and slows the metabolism of cholesterol, causing it to accumulate faster on the walls of arteries.

Dr. Hazen said in the news release issued by Nature, that “the study could signal a new approach to diet and health.”

“In some cases, an individual’s collection of intestinal microbes may be as important to their diet as anything on a nutrition label,” he said. “Bacteria make a whole slew of molecules from food, and those molecules can have a huge effect on our metabolic processes.”

Results of related experiments that the researchers performed on mice suggested that control of the culprit bacteria in the gut – through antibiotics or probiotics – may be able to eliminate the bad effect of consuming L-carnitine. “When the animals were treated with gut-clearing antibiotics, l-carnitine in the diet did not encourage plaques,” the Nature release said. These mouse studies, however, were preliminary, and further study will be required to see if the same results can be achieved in humans, and whether this could lower the heart risk of consuming red meat and other carnitine-containing foods and supplements.

Meanwhile, Dr. Hazen says that as a result of the study findings, he has drastically reduced his own consumption of red meat. He also warns against taking supplements containing carnitine - which, according to the Nature release, “are marketed with the promise that they promote energy, weight loss and athletic performance.”

The Study; Methods and Findings
As part of the study, Hazen and his colleagues had a group of 77 volunteers consume the nutrient l-carnitine - found in red meat and dairy products - along with a capsule that would attach to and label the carnitine for easy detection. The group included 26 people who were vegetarians. One committed vegan (who had not consumed meat in at least one year) agreed to eat a 200-gram sirloin steak, as part of the study.