You probably heard the news last month about the study that showed L-carnitine in red meat is dangerous. Based on this study published in Nature Medicine, some of my readers expressed concerns about taking supplements containing acetyl-L-carnitine.
But let me assure you, it’s not a problem. This small study has been hyped into fear-mongering headlines that have no basis. The story is that the carnitine in red meat gets metabolized by certain bacteria in the gut into a compound called Trimethylamine N-oxide (TMAO), which causes atherosclerosis (in mice).
First, this study involved only six people and some mice. Most of the data and conclusions came from the mice, which were genetically engineered to develop heart disease.
Also, previous studies have shown that eight ounces of carnitine-rich foods, including red meat, produced no more TMAO than common fruits and vegetables. In fact, one study showed that tomatoes, soybeans, potatoes, peas, peanuts, and cauliflower produced more TMAO than beef. The amount produced after eating chicken was almost equal to that of beef. These same studies also showed that mushrooms, bread, eggs, and cheese produced higher levels than beef.
The greatest food source of TMAO was actually seafood. Halibut produced over 100 times as much TMAO as beef. In this 1999 study, over 46 different foods were tested, and with the exception of seafood, there were no other foods that generate significantly less TMAO formation than red meat.
Numerous studies have confirmed the cardiovascular benefits of consuming fish and other seafood. The fact that seafood produces levels of TMAO far in excess of that produced by red meat should alone call into question the conclusions of this one study.
There are dozens of other questions about how this study was conducted and interpreted, and there are numerous studies and clinical trials that show carnitine supplementation is beneficial not just in the treatment of cardiovascular disease, but also in prevention. If red meat was the culprit (which it is not), then based on the same data and reasoning, seafood would be the greatest dietary contributor to heart disease ever discovered. We know that’s not the case.
If eating red meat poses a danger, it would be from contaminants and residues it might contain, such as hormones, antibiotics, and pesticides. But that is true of all other meat, as well as fruits and vegetables. And that’s why wild game and homegrown (or organically grown) vegetables and fruits are often the safer option.
This study also highlighted the fact that intestinal bacteria were involved in the conversion of these various compounds. In fact, antibiotics were actually used to destroy the intestinal flora to see what effects it would have on TMAO production. This is questionable. Research shows it can take as long as two years for bacteria flora to return to normal after a round of antibiotics. I’m sure those in the study weren’t given that long to recover before undergoing additional testing.
To single out one component like carnitine from one complex food like red meat and indict it as the cause of heart disease is absurd. Science, and hopefully common sense, tells us that our foods are complex combinations that work synergistically to achieve a long list of biological effects.
There’s nothing in this over-hyped study to give us any reason to avoid red meat or acetyl-L-carnitine supplements.
Now it's your turn: What is your takeaway from these study results?