Green Light

What Is The Truth About Carnitine And Heart Disease?

Is carnitine good for you? With respect to this question, the conclusions of this review are similar to the conclusions of other health experts.

For example, in their Fact Sheet On Carnitine For Health Professionals the NIH states “Some athletes take carnitine to improve performance. However, twenty years of research finds no consistent evidence that carnitine supplements can improve exercise or physical performance in healthy subjects—at doses ranging from 2–6 grams/day administered for 1 to 28 days. For example, carnitine supplements do not appear to increase the body’s use of oxygen or improve metabolic status when exercising, nor do they necessarily increase the amount of carnitine in muscle.”

The NIH fact sheet goes on to list some diseases causing muscle loss or muscle weakness, for which L-carnitine supplementation is appropriate. However, in these cases, the carnitine supplementation should be recommended by health professionals.

Is carnitine bad for your heart? The link between carnitine and heart disease risk is a bit more complicated. As I mentioned above, there is an association between red meat consumption and blood TMAO levels and an association between blood TMAO levels and heart disease.

Is it TMAO that increases the risk of heart disease or is it some other component (saturated fat, for example) of red meat that increases the risk of heart disease? Nobody knows. More research is needed.

There is also a “red herring” that complicates the TMAO story. It turns out that TMAO helps fish survive the high pressures they encounter in the deep ocean. Thus, many fish are high in TMAO, and fish consumption also increases blood TMAO levels.

Are the bad effects of TMAO in fish outweighed by the heart healthy components in fish (omega-3s, for example)? Nobody knows. More research is needed.

To summarize:

1) There is no reason to take L-carnitine supplements unless directed by your health professional. There is little evidence they will help your physical performance. There is also no good evidence to support the other benefits of L-carnitine you find listed on Dr. Strangelove’s blog or the website of your favorite supplement company.

2) L-carnitine supplements may be bad for your heart, but much more research will be needed to be sure. [Note: Based on what we know about the role of gut bacteria in TMAO production, vegans could probably take L-carnitine supplements without causing an increase in TMAO levels. However, that is probably a moot point. There is no evidence that L-carnitine is more effective for vegans than it is for omnivores.]

The Bottom Line

If you are a weightlifter or bodybuilder, chances are you are taking an L-carnitine supplement, or a protein shake fortified with L-carnitine. That is because L-carnitine has been promoted for increasing muscle mass and physical performance for so long that most people have come to believe it must be true. Is it true, or is it just another food myth?

On the flip side, recent studies have suggested that the carnitine in red meat might be bad for your heart. Could the same be true for L-carnitine supplements? Could they also be bad for your heart?

A recent review looked at these questions. Here are the conclusions of the review:

Participants receiving L-carnitine alone had no increase in muscle carnitine content.Participants receiving L-carnitine + 80 grams of carbohydrate had around a 10% increase in muscle carnitine content. [To put that into perspective, 80 grams of carbohydrate is roughly equivalent to 2 cups of white rice or two medium potatoes.]There was no significant effect of L-carnitine on muscle mass or physical performance. [This is logical, given the minimal effect of L-carnitine supplementation on muscle carnitine levels.

Thus, this review found little evidence that L-carnitine supplementation was beneficial. It resulted in little or no increase in muscle carnitine levels or in physical performance.

This review also found that L-carnitine supplementation resulted in a significant increase in plasma TMAO, a compound that has been associated with an increased risk of heart disease.

Thus, this review found some evidence that L-carnitine supplementation might be bad for you.

The NIH has also issued a fact sheet for health professionals summarizing research on L-carnitine over the past 20 years. The conclusions from their fact sheet can be best summarized as:

1) There is no reason to take L-carnitine supplements unless directed by your health professional. There is little evidence they will help your physical performance. There is also no good evidence to support the other benefits of L-carnitine you find listed on Dr. Strangelove’s blog or the website of your favorite supplement company.

2) L-carnitine supplements may be bad for your heart, but much more research will be needed to be sure.