The L-Carnitine Debate

Athletes looking to improve mitochondrial function for energy metabolism have likely heard of the supplement L-Carnitine. A quick google search will yield advice in either direction as to the safety of taking L-Carnitine. Here, we’ll review the reported benefits, concerns, and take-aways of this non-essential amino acid.

What is it?

L-Carnitine is an amino acid (building block for protein) that is naturally produced in the body. Since it is produced by the body, it is considered non-essential. The body is able to produce L-carnitine with the use of two other amino acids – lysine and methionine.

L-Carnitine’s Basic Role in the Body

• Transports fatty acids across the mitochondrial membrane and into cells where it is converted to energy
• Assists with the removal of toxins from inside the mitochondria, helping to mediate toxic stress

Uses in Certain Populations

With the function of converting fatty acids into energy, L-carnitine has been promoted to athletes as a supplement to aid in muscle recovery, increased stamina, and oxygen supply to the muscles. However, when considering dietary sources of L-carnitine, such as red meat, we need to look at the food as a whole.

Red meats are also a source of heme-iron, which helps promote red blood cell formation. This should be considered as a supportive way that the body is able to increase oxygen supply to the muscles therefore helping to improve muscle recovery.

Medical research is looking into L-carnitine’s potential benefits for cardiac and renal (kidney) disease patients. Although research is promising, it should be recognized that supplementation is most beneficial when patients have a known depletion related to cardiac events or treatments such as dialysis.

Concerns with Dietary vs Synthetic Supplementation

Conflicting evidence is partially due to the fact that “L-carnitine is metabolized by the intestinal microbiotia to trimethylamine-N-oxide, an atherogenic substance which increases risk of cardiovascular disease.”

What this means is that excess dietary intake of L-carnitine when a known insufficiency isn’t evident may cause harm to the cardiovascular system in the long run. Why you may ask? When people increase their intake of red meats they also increase their intake of saturated fats. Depending on the cut of the meat, the saturated fat content may be higher than recommended, which may lead to poor cardiac function over time. Synthetic supplementation, on the other hand, does not come with the additional saturated fats and therefor does not impose this risk. It must be mentioned that bioavailability of synthetic L-carnitine is shown to be less (14-18%) than dietary L-carnitine (54-87%) in one study.

Key Take-Aways

• L-Carnitine does play a role in positive cardiovascular and metabolic functions.
• The positive effects associated with L-carnitine from red meats must also take into account red meat’s contribution of heme-iron which aides in increased blood volume, a benefit for muscle recovery.
• The positive effects from red meats as a source of L-carnitine must also factor in the saturated fat content of red meats.
• Supplementation with synthetic L-carnitine has shown benefits in populations with known depletion.
• As with any synthetic supplementation, bioavailability is often less than with dietary sources.
• L-carnitine is a non-essential amino acid which the body is able to create on its own from other amino acids and is not required through additional foods or supplements unless there is a known deficit, such as someone on a vegetarian or vegan diet.

Dietitian Summary

When it comes to supplements for athletes, I always recommend looking at whether or not we can get the desired component through food. The body’s ability to utilize any nutrient is always going to be optimal through food because that is what our bodies were designed to do.

If an amino acid like L-carnitine is something you are interested in, evaluate your diet to see if you are getting adequate amounts. L-carnitine sources are meat, poultry, fish, and dairy. If you regularly incorporate these into your week, you are likely getting adequate amounts.

Always consider the whole package when it comes to food sources. Foods like fish and poultry, low fat dairy, and lean cuts of red meat will have less saturated fat content, so the negative components of the food are lessened. As always, incorporating lots of leafy green vegetables, colorful vegetables, omega-3 fatty acids, and fruits helps the body’s overall picture of optimal performance.

If you are going to start taking a supplement, evaluate your progress over the course of time. Without changing anything else, do you see improvements in your performance and recovery. Again, keep in mind that this is without changing any other factors, so be aware of false positive that may have occurred because you also started a new training routine, focused more on your sleep, or are experiencing a placebo effect.

At the end of the day, for me, it comes down to getting everything I can through food first. Supplements are expensive and without absolute known effects I want to keep excess costs down.

Check out this week’s Food of the Week where we talk about a lean cut of red meat (Venison) and show you ways to incorporate this L-Carnitine source as part of your overall whole food approach. And don’t miss last week’s Lentils.