Over the last decade the number of articles focusing on our microbiota - a term that refers to vast number of bacteria that colonize our bodies- has grown rapidly. Recently, some of these studies are attracting considerable public attention because of their relevance to human health - and the potential that they may represent targets for treatment.

Now, on the heels of a recent study showing that you could manipulate a person’s intestinal bacteria and resolve a diarrheal illness better than a common antibiotic, we have a report by investigators from the Cleveland Clinic that gut bacteria may have a role in heart disease.

The gut bacteria can metabolize substances and, as a byproduct, produce other substances. Some of these bacteria, in the course of metabolizing dietary L-carnitine, a substance found in red meat, produce a substance called TMAO that was shown to promote atherosclerosis in mice. Also, L-carnitine blood levels were shown to be associated with heart disease in individuals who had bacteria that produced the TMAO. The implication was that the L-carnitidine was only a problem in individuals with the intestinal milieu to convert it to TMAO, which is the possible real culprit.

So what are the 3 things you should know now?

First, the study, while important and potentially groundbreaking, needs replication. In the end it is a rather small study of people - and a small number of mice - and is supportive of the theory that red meat may cause heart disease because of actions of the intestinal bacteria. Before we start measuring the gut microflora to determine if you can safely eat meat, we have a lot more work to do. This study needs to be replicated by others and we need to determine how such knowledge may be translated into action that might actually help people. But this studies establishes the plausibility of this theory.

Second, you should not fear red meat. The study starts with the presumption that red meat causes heart disease, but the medical literature is actually has a lot of conflicting information. A prominent study of the medical literature by investigators at Harvard concluded that the consumption of red meat was not associated with a higher risk of heart disease.  They based their conclusions on 20 studies that included more than a million individuals. They did find that processed meats carried some risk. Clearly, we have a lot to learn about the relationship of certain dietary habits and cardiovascular risk.

Third, it’s time to really understand the risks and benefits of many of the food supplements. These substances often escape close scrutiny because they are not understood to be drugs - but they have the potential for adverse effects. Many people take supplements that contain L-carnitine. This study suggests the possibility that some of those individuals, the ones with the gut bacteria that convert it into TMAO, might be increasing their risk of heart disease. Meanwhile, the evidence of benefit for L-carnitine is not based on the kind of large studies that we expect of our drugs - the studies have tended to be small. Maybe it is time to be more vigilant about assessing the safety of these supplements.

So are your gut bacteria putting you at risk for heart disease? Well, if you consume food or supplements with L-carnitine - and have acquired gut bacteria that will convert it into TMAO - then the answer now is maybe - and in the future we may be assessing your gut bacteria to determine what you can safely eat - at least its possible that we will - even if it is far from certain.

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Harlan Krumholz, Contributor