So, L-carnitine is a popular fat burner, the effectiveness of which for weight loss and muscle gain is not confirmed.
For those who still want to experiment with it, we have gathered some facts about the possible harm of L-carnitine and its side effects. Despite being a natural substance, there are reasons for concern.
Main thoughts:
Side Effects of L-Carnitine
Most scientific studies confirm the relative safety of L-carnitine for human health and the absence of serious side effects.
In one study on the side effects of L-carnitine, participants took 3 grams every day for 21 days, and to assess possible harm, a thorough blood analysis was conducted at the beginning and end of the experiment. No negative side effects were found 3
The safety of L-carnitine at a dose of 2 g per day is confirmed in a meta-analysis of scientific studies on the harm of L-carnitine. However, in some experiments, side effects such as nausea and stomach discomfort were noted 2,4.
For most people, a dose of 2 grams of carnitine per day is safe.
When exceeding a dosage of 3 g, the likelihood of experiencing unpleasant side effects such as nausea, vomiting, abdominal cramps, diarrhea, and a fishy odor from the mouth is very high 1,5.
Most scientific studies indicate that a dose of L-carnitine of 2 grams per day is well tolerated and safe. Occasionally, nausea and stomach discomfort are noted, but serious side effects are not typical for L-carnitine
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Contraindications of L-Carnitine
L-carnitine is contraindicated for people with kidney diseases or muscle cramps, as it can exacerbate these conditions in large amounts.
Considering the above, we would recommend refraining from its use for those who hope to lose weight with its help or gain muscle mass, due to its unproven effectiveness.
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The most dangerous side effect of L-carnitine: harm to the heart
Despite L-carnitine’s property of improving cardiovascular function, its use can have the opposite effect.
One of the most serious and dangerous side effects of carnitine is an increased risk of cardiovascular diseases.
This statement contradicts the earlier claim about the absence of serious side effects of L-carnitine; however, the reason lies not in the carnitine itself, but in the products of its metabolism.
Researchers at the Cleveland Clinic found that the metabolic products of carnitine increase the risk of developing atherosclerosis (“blockage” of blood vessels). Their research findings can be summarized as follows 6:
“L-carnitine itself is not dangerous, as noted above.
What is dangerous is what happens to it when it enters the intestine: when you eat meat or take an L-carnitine tablet, certain bacteria in the intestine produce a chemical substance called trimethylamine (TMA), after which the liver converts it into trimethylamine N-oxide (TMAO).
This byproduct, TMAO, stimulates the development of atherosclerosis.“
These conclusions are based on blood composition analysis from over 2500 patients, including omnivores, vegetarians, and vegans (recall that carnitine is found in large amounts in red meat), as well as an experiment on mice that were fed a diet high in carnitine while artificially suppressing the concentration of bacteria that convert carnitine to TMAO.
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The study on mice found that TMAO affects cholesterol metabolism, which is known to be the main cause of atherosclerosis.
The higher the level of carnitine in the blood, the greater the risk of cardiovascular diseases: heart attack, stroke, and ultimately, death.
The level of TMAO in the blood of vegans and vegetarians is significantly lower.
“The bacteria living in our digestive tract are a result of long-term dietary habits.
A diet rich in carnitine alters the bacterial composition, increasing the proportion of those bacteria that “love” carnitine, which creates conditions for an increase in the blood levels of TMAO and the risk of thrombus formation in the vessels.
At the same time, in the blood of vegans and vegetarians, TMAO is formed in lower concentrations, which likely explains the cardiovascular health benefits of a vegetarian diet.
L-carnitine is a relatively safe substance; however, its regular consumption can lead to the development of a very serious side effect: atherosclerosis (artery blockage), caused by the byproducts of carnitine metabolism.
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In summary: what we know about the harm of L-carnitine
Despite the fact that L-carnitine is a natural substance found in many foods, its use as a supplement can pose health risks.
The list of side effects of L-carnitine includes both relatively harmless ones (stomach discomfort and nausea) and the risk of developing atherosclerosis and related conditions such as heart attack, stroke, and death.
