Are Carnitine Supplements Good For You Or Bad For You?

What Is The Truth About Carnitine And TMAO?

BodybuilderIf 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?

If you visit Dr. Strangelove’s website, you may also be told that carnitine supplementation is beneficial for weight loss, migraines, baldness, ADHD and autism, chronic fatigue syndrome, and/or low energy, muscle loss, and cognitive decline in older adults. Are these claims fact or fiction?

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 carnitine supplements? Could they also be bad for your heart?

A recent systematic review (AG Sawicka et al, Journal of the International Society of Sports Nutrition, 17: 49, 2020) of L-carnitine supplementation answers these important questions. The authors called their study “The bright and dark sides of L-carnitine supplementation” because they set out to systematically investigate the benefits and potential risks of L-carnitine supplementation.

But before I share the results of this study, I need to give you a little background on L-carnitine. It is time for another Biochemistry 101 segment.

Biochemistry 101: What You Need To Know About Carnitine

professor owlCarnitine plays an essential role in human metabolism. It is required for transport of fatty acids into our mitochondria so they can be used to generate energy. Without carnitine we would be unable to utilize most of the fats in our diet as an energy source.

As you might expect, carnitine is essential for any tissues that have mitochondria, but it is particularly important for high energy tissues like skeletal and heart muscle.

For most of us, our liver and kidneys make all the carnitine we need. So, we don’t really need carnitine from food or supplements.

However, we do get significant amounts of carnitine from red meat, much smaller amounts of carnitine from other animal foods, and almost no carnitine from plant foods. Adults consuming diets with red meat and other animal foods get about 60-180 mg of carnitine a day from their diet, whereas vegans only get around 10-12 mg/day.

Uptake of carnitine from the blood into muscle tissues requires insulin. Thus, carnitine uptake into muscle is significantly less on a low-carbohydrate or keto diet than it is on a mixed diet containing carbohydrates.

Finally, our kidneys do an excellent job of regulating blood carnitine levels, with excess carnitine being excreted into the urine. Thus, total body carnitine levels are virtually the same with high-carnitine and low-carnitine diets.

Question MarkThis raises the question: “Are L-carnitine supplements good for you?”

Now, let’s talk about the dark side of carnitine. I have discussed this in a previous issue of “Health Tips From the Professor”. Here is a brief summary:

  • People who eat a lot of red meat harbor a species of bacteria in their intestine that converts carnitine to trimethylamine (TMA). We don’t know whether this species of gut bacteria is favored by the presence of red meat in the diet or the absence of certain fruits, whole grains, and legumes from the diet of meat eaters.
  • The TMA is reabsorbed into the bloodstream, and the liver converts TMA to TMAO (trimethylamine N-oxide).
  • TMAO is associated with an increased risk of heart attack, stroke, and heart failure.

When you think about it, this is a perfect example of double jeopardy. Red meat is high in carnitine, and red meat eaters have gut bacteria that result in carnitine being converted to a compound that may increase the risk of heart disease.

This raises the question: “Are L-carnitine supplements bad for you?”

Let’s look at these two questions. First, I will discuss the recent review. Then I will put the conclusions of that review into perspective by looking at what other health experts say.

Are Carnitine Supplements Good For You Or Bad For You?

good news bad newsMost previous studies of carnitine supplementation have lasted only two or three weeks, which may not be long enough to measure an effect of carnitine supplementation on performance. So, the authors of this review paper selected studies that lasted 11 weeks or more for their review.

The review included 11 studies. They lasted either 12 or 24 weeks. Participants received doses ranging from 1 gm to 4.5 gm of L-carnitine per day. 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.]
  • One study compared male vegetarians with male omnivores. The omnivores had no increase in muscle carnitine content, but the vegetarians did. [The study did not analyze the diets of the omnivores and vegetarians, but it is probably safe to assume that the carbohydrate content was higher on the vegetarian diet.]
  • 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 good for you. It resulted in little or no increase in muscle carnitine levels or in physical performance.

  • Two of the 11 studies measured plasma TMAO levels. These studies found that L-carnitine supplementation resulted in a significant increase in plasma TMAO levels.

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

What Is The Truth About Carnitine And TMAO?

the truth signIs 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 you? The TMAO story 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:

  • 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.
  • 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:

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

For more details read the article above.

These statements have not been evaluated by the Food and Drug Administration. This information is not intended to diagnose, treat, cure or prevent any disease.

Are Fat Burning Sports Supplements Safe?

It’s Buyer Beware in the Sports Supplement Market

Author: Dr. Stephen Chaney

Muscular man holding container of training supplementsFor many athletes it’s all about being bigger, faster, stronger. That’s what makes the fat burning sports supplements so appealing. If you believe the ads, they will burn fat, increase muscle mass and give you an energy boost. But, are fat burning sports supplements safe? Are they effective?

What Are Fat Burning Sports Supplements?

Simply put, most of the fat burning sports supplements contain metabolic stimulants of some kind. That’s where the energy and fat burning claims come from. The stimulants range from clearly ineffective to downright dangerous.

Are Fat Burning Sports Supplements Effective?

Because sports supplements are considered to be foods rather than drugs, the FDA cannot require sport supplements manufacture to prove that their products are either safe or effective. As a consequence, most sports supplement manufacturers don’t conduct clinical trials to prove the effectiveness of their products. Their claims are based on animal studies and testimonials. However, in most cases there is no objective evidence that their supplements actually work.

Are Fat Burning Sports Supplements Safe?

All stimulants carry some risk. Even small amounts of caffeine can be problematic for some individuals, and many sports supplements contain massive amounts of caffeine. But, it is not caffeine containing sports products that are the most worrisome.

Many sports supplement manufacturers are firm believers in the “better living through chemistry” motto.

  • They start with an herbal ingredient that has stimulant properties
  • They synthesize what they think is the active ingredient
  • Perhaps they chemically modify it a bit….
  • ..and, Voila! They have a proprietary new sports supplement
  • They label it a fat burner, prepare their claims and they’re ready to go to market

And, why bother testing it? Unless the product kills or seriously harms people, the FDA can’t step in and tell a manufacturer to take their product off the market.

And, if you think that the manufacturers and sellers of the product are looking after your best interests, think again.

Case Study #1: Jack3D and DMAA

I told you about this story last year, so I’ll just give you a brief recap here.

  • After a couple of marines died after using Jack3D prior to a workout, the US military ordered that the product not be sold on their bases. The manufacturer continued to make the product. GNC stopped selling it on military bases, but continued to sell it in all its other stores.
  • Eventually the FDA stepped in and recommended that Jack3D not be sold. The manufacturer claimed that the active ingredient, DMAA, was found in the geranium extract they used in their product. Since that was a food ingredient, they claimed the FDA did not have jurisdiction.
  • The FDA denied that claim based an extensive testing of geranium extract. At that point the manufacturer stopped making it (They have since resuming making the product with yet another poorly tested stimulant). GNC said they would stop selling Jack3D “as soon as their inventory was used up”.
  • The FDA finally had to raid the GNC warehouses to get the product off the market.

Case Study #2: OxyElite Pro and Aegeline

In case you thought that was an isolated case, the same sports supplement manufacturer has recently been involved in a second case that sounds all too familiar.

  • The FDA recently advised consumers to stop using OxyElite Pro after reports of 24 cases of acute non-viral hepatitis (a very rare disease) in users of that sports supplement in Hawaii. Two of those patients required liver transplants, and one of them died.
  • In this case the manufacturer stopped domestic distribution of the product, but argued that the product is safe. They claimed that counterfeit versions of OxyElite Pro were being sold in the US market.
  • On October 11, 2013 the FDA sent a warning letter to the manufacturer stating that the active ingredient, aegeline, was not a lawful dietary ingredient. The manufacturer replied that it was a natural constituent of the citrus fruit tree Bael. (I’m not sure why that makes it safe. I don’t know about you, but I don’t eat a lot of Bael fruit.)
  • As of a few days ago England, Denmark, Spain, Australia & New Zealand have warned consumers in those countries not to use OxyElite Pro.

It’s too early to tell how this story is going to turn out, but my money is with the FDA.

Case Study #3: Craze and DEPEA

And, in case you thought the problem was with a single rogue manufacturer, there is a developing story around yet another popular sports supplement, Craze, made by a different manufacturer.

  • Researchers from the NSF, Harvard and the National Institute for Public Health in the Netherlands recently published a paper claiming that Craze contained DEPEA, a methamphetamine-like compound.
  • The manufacturers claimed that the researchers did the chemical analysis incorrectly and their product actually contained a close analog of DEPEA that is found in dendrobium orchids. (Again I’m not sure why that makes it OK. I don’t think people eat a lot of dendrobium orchids either).

Stay tuned. I’m sure this story will have some interesting twists before it’s finished.

The Bottom Line:

1)     In the sports nutrition industry, it is buyer beware. There are lots of rogue manufacturers out there who care more for their bottom line than your well being. Do your homework and search for reputable companies with a long track record of product quality and ethical standards. There are some out there.

2)     Ignore the outlandish claims, no matter how appealing. Once again, stick with establishing companies with a track record of product integrity. Only use sports supplements that are backed by clinical studies showing that they are both safe and effective.

3)     Be particularly cautious about sports supplements that claim to burn fat or give you energy. They generally contain metabolic stimulants, and often those stimulants are poorly characterized. Most have not been proven to be effective, and some have the potential to do more harm than good.

4)     Fat burning supplements are often cross marketed as weight loss supplements. They are just as dangerous for dieters as they are for athletes.

5)     Don’t assume that just because the ingredients supposedly come from a natural source (geraniums, Bael trees or dendrobium orchids, for example) they are safe.

These statements have not been evaluated by the Food and Drug Administration. This information is not intended to diagnose, treat, cure or prevent any disease.

Use of Sports Supplements By Young Athletes

Are Sports Supplements Effective? Are They Safe?

Author: Dr. Pierre DuBois

plate-of-pills-200-300In recent years, the use of sports supplements by young athletes has increased dramatically. The most commonly used sports supplements among teenagers of all ages were vitamins and minerals, though “ergogenic aids” are used by some teen athletes specifically to enhance performance. Among these performance-enhancing supplements  are substances such as caffeine, creatine, ephedra and other stimulants, human growth hormone (HGH) and anabolic steroids.

Of the vitamin and mineral supplements, mutivitamins, vitamin C, calcium and iron were reported as being taken most often. While the risks of taking vitamin supplements is relatively low, there is some concern that young athletes may then progress to taking more dangerous substances under the impression that they are as harmless as vitamins and minerals. And while the risk of overdose with vitamins and minerals is low, it is not nonexistent, and some vitamins can be toxic when too much is taken (such as iron and vitamin A) or may interact with other vitamins or drugs.

Although many performance-enhancing supplements are advertised as being safe – especially those made from natural compounds –  a great number of them have not been tested by any regulatory agency, so their actual safety is not known. In addition, there are no formal guidelines for dosage in many cases, so there could be adverse side effects if too much is inadvertently taken.

The pressure to excel at sports is greater than ever, and there is increasing competition to get into elite sports programs where they have a better chance of being discovered by professional sports scouts looking for the next big star. The possibility of fame and fortune can be a strong enticement to young athletes to try performance-enhancing supplements to give them an edge over their competition. And often it is their coach that suggests or encourages this practice.

According to studies done on high school athletes, they report taking supplements to not only enhance performance, but also to encourage growth and muscle development, prevent illness and reduce fatigue. Supplement use was greatest among athletes who practiced two or more different sports and those who were required to “bulk up”, such as wrestlers and weight lifters.

While the opinions of friends, teammates and coaches were a big influence on the decision of young football players to take supplements (particularly creatine), it was their parents who had the greatest amount of influence on their decision. So it is incredibly important for parents to be educated as to the benefits and drawbacks of each of these supplements for young athletes.

The Bottom Line:

  • There is tremendous pressure on teenage athletes to qualify for elite programs that will increase their chances of being selected for the top college teams and eventually getting onto professional teams. Because of that, the use of sports supplements by teenage athletes is commonplace.
  • Vitamin and mineral supplements are generally harmless unless taken in excessive amounts.
  • Performance-enhancing sports supplements, on the other hand, are poorly regulated. Many are useless and others are potentially harmful. In next week’s “Health Tips From The Professor”, I’ll give you some examples of sports supplements you might want to avoid.
  • If you are the parent of a teen athlete, have a conversation with your child about supplements. Don’t lecture, but involve them in the process of doing research. You may be surprised what you both find.

These statements have not been evaluated by the Food and Drug Administration. This information is not intended to diagnose, treat, cure or prevent any disease.

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