Dietary supplements are widely marketed as performance and recovery supplements in the fitness world. One such supplement is L-carnitine. This compound is advertised to increase energy levels and support muscle recovery, which makes it a popular addition to the fitness routine of athletes and other people who exercise in the gym regularly. But new findings have raised concerns about a potential association between L-carnitine and heart disease. So far, a new study suggests that combining L-carnitine with pomegranate may help mitigate these risks.
L-carnitine is a natural nutrient that is synthesized in low quantities by the human liver, brain, and kidneys. First discovered in meat in 1905 and later identified in humans in 1952, it was initially confused with a vitamin and called vitamin BT. Today, it is available as an over-the-counter product and is also present in trace quantities in animal-based foods like red meat and dairy products.
The concern arises when L-carnitine is consumed in supplement form. The percentage that the body absorbs is less than 20%. The unabsorbed portion reaches the colon, where gut microbes convert it into trimethylamine (TMA). This compound is then absorbed into the bloodstream and metabolized in the liver into trimethylamine N-oxide (TMAO). High TMAO levels have been associated with the subsequent elevated risk of cardiovascular disease, including blood clots.
This microbial transformation is the main issue because the L-carnitine produced by the body itself or consumed from meat does not often lead to dangerous TMAO levels. The highest risk stems from unabsorbed supplemental L-carnitine in large doses.
Scientists at the Quadram Institute in Norwich, UK, may have found a potential solution. In an in-vitro study, the researchers examined the reaction of gut microbes to L-carnitine in the presence and absence of a pomegranate extract, a substance containing ellagitannins, a special polyphenol with antioxidant and anti-inflammatory capacities.
The results were significant. Upon the addition of pomegranate extract, the level of TMA formed by the gut microbes was substantially reduced. Ellagitannins, which largely remain undigested until they come into the colon, seem to behave in a manner that restricts their capacity to metabolize L-carnitine into dangerous products using the gut microbiota.
The study’s lead researcher noted that the experiments implied that the adverse outcomes of L-carnitine supplementation would be decreased through the consumption of pomegranate or other ellagitannin-rich foods. This might be a useful dietary plan to prevent cardiovascular diseases.”
Importantly, ellagitannins are not found in pomegranates. They are also present in raspberries, strawberries, and walnuts, which makes it simpler to incorporate these protective foods into everyday meals.
A clinical trial has now been initiated to test these results in human volunteers. If the results translate to real-life settings, they could significantly affect how supplements like L-carnitine are prescribed, especially for individuals concerned about long-term cardiac health.
In the meantime, adding more fruits and nuts to your diet appears to be a relatively simple but potentially powerful preventive step. It is true that finding a healthy balance between dietary supplements and whole food nutrition may be the key to maximizing the benefits while minimizing health risks.
References: Haarhuis J. Why the L-carnitine sport supplement is controversial. The Conversation. Published July 3, 2025. Accessed July 7, 2025. https://theconversation.com/why-the-l-carnitine-sport-supplement-is-controversial-219520
