Yesterday, a customer with heart-health issues came to you looking for advice. You happily ran off the litany of heart-healthy choices she could make. "Eat less saturated fat, exercise, take a multivitamin, don't forget your carnitine, take garlic, eat lots of fiber..." and on you went. What's that? You didn't mention carnitine? Never heard of it or thought it was only for weight lifters? In that case, it's time you learned the facts.
Carnitine is a hard-to-classify, but essential, nutrient. It is often called an amino acid but is actually a vitaminlike substance—related to the B vitamins and similar in form to amino acids. It is not usually considered an essential nutrient because the body synthesizes it from the amino acids lysine and methionine when enough niacin, vitamins B6 and C and iron are present. Carnitine comes in several forms, with L-carnitine—the form your body produces—being the most important.
In 1905, carnitine was first isolated from beef. Its name is from the Latin carnus, which means flesh. As the name implies, animal products are the primary sources of carnitine, although other foods do contain the nutrient at much lower levels. For instance, 3 ounces of steak contain 81 milligrams, 8 ounces of milk contain 8 milligrams and a medium avocado has 2 milligrams. Mutton contains the most carnitine for those looking to load up.
The science of carnitine is fairly complex, but if you remember your high school science, then the Krebs cycle should ring a bell. This is the process by which energy is produced in the mitochondria, each cell's powerhouse. Carnitine plays the central role of transporting long-chain fatty acids into the mitochondria where ATP (adenosine triphosphate), the currency of energy, is produced in the Krebs cycle.
Cardiologist and author Stephen T. Sinatra, M.D., in his booklet L-Carnitine and the Heart (Keats Publishing, 1999), co-written with Jan Sinatra, R.N., uses a simple analogy. "L-carnitine functions like a freight train, transporting crucial fatty acids across the mitochondrial membrane to be burned as fuel," he writes. Carnitine then shuttles compounds out of the mitochondria that would become toxic if allowed to build up. In short, forget "no pain, no gain" and think "no carnitine, no energy" instead. (Actually, researchers at the National Academies of Science in Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium, and Carotenoids suggest that one of the early symptoms of vitamin C deficiency is fatigue. That's because C plays a role in carnitine production.)
But what does carnitine have to do with heart health, you ask? Reto Rieder, director of nutrition for Lonza Inc. North America, based in Fair Lawn, N.J., and the manufacturer of L-Carnipure, puts it this way. "Most people do not realize that the heart obtains 70 percent of its energy from fat breakdown," he says. "The fundamental role L-carnitine plays in energy metabolism, together with the dependence of the heart on fatty acid breakdown for energy production, make L-carnitine a crucial energy provider for the heart."
Carnitine research is also showing promise for liver health and Alzheimer's disease, but heart health is where carnitine especially looks to be a major player for the future.
Hemmi Bhagavan, Ph.D., director of the department of nutrition science for Westbury, N.Y.-based Tishcon Corp., notes the nutrient has numerous cardioprotective uses. "For carnitine, there is no doubt as to potential clinical benefits, especially in heart disease," he says. "There's a lot of material in the scientific journals [on carnitine's benefit for] intermittent claudication [atherosclerosis-induced leg pain], angina pectoris [chest pain] and congestive heart failure." Bhagavan also cites newer studies showing evidence that carnitine can help maintain healthy cholesterol and blood lipid levels. Prevention of arrhythmia, or irregular heartbeat, and lowering blood pressure are other areas where carnitine looks to be useful.
Indeed, in a 1991 study published in the journal Drugs Under Experimental and Clinical Research, researchers found that patients with angina were able to exercise without chest pain when taking 2 grams of carnitine daily. In 1994, researchers writing in the European Heart Journal reported 1.5 grams daily of carnitine works to improve congestive heart failure symptoms. The Journal of the American College of Cardiology published a study in 1995 in which researchers showed that individuals with intermittent claudication experienced a 73 percent improvement in walking distance when they took 2 grams of carnitine daily. And, in 1992 and 1995 respectively, Drugs Under Experimental and Clinical Research and the Journal of the American College of Cardiology published studies showing significant improvements in survival rates as well as improvements in heart rate, blood pressure, angina and blood lipids among those taking 4 grams of daily carnitine immediately following a heart attack.
"Most people do not realize that the heart obtains 70 percent of its energy from fat breakdown."As the small but significant amount of science continues to mount supporting carnitine's use in heart health, the question becomes: What are the downsides to taking carnitine? So far, it seems there are few contraindications. There are drug interactions, so consulting a doctor is a must. Sinatra says he has seen some thyroid function disruption in patients taking high doses of carnitine, so patients and their health care providers must be vigilant. Large doses of carnitine—say, 500 mg and above—can also cause some gastrointestinal tract discomfort, most likely in the form of diarrhea. However, these GI irritations may be less common with a newer form of carnitine, L-carnitine fumarate, patented by Sigma-Tau, based in Gaithersburg, Md.
To date, there is no recommended carnitine dose established either for daily or acute-case supplementation. Your Complete Guide to Vitamins and Supplements (Prima Publishing, 1999) by Angelo DePalma, Ph.D., offers a range of 1 to 3 grams daily for therapeutic use. Sinatra says he recommends upwards of 4 grams for some patients. In his book, DePalma writes: "A few individuals have a genetic defect that hinders the body's ability to make carnitine. In addition, disease of the liver, kidneys, or brain may inhibit carnitine production."
Vegans and strict vegetarians should make sure they're getting enough carnitine. Although both Bhagavan and Sinatra say these populations are at risk for carnitine deficiency, Oregon State University's Linus Pauling Institute recommends that even they can synthesize enough carnitine from diet. Reminding vegan and vegetarian customers to maintain a healthy balance of foods is probably the best advice.
One interesting potential application for carnitine is its use in combination with another heart-health supplement, Co-Q10. Sinatra describes the two as his "twin pillars of healing" when it comes to heart disease prevention and healing. There is little scientific evidence to support the combination in relation to heart disease, but both supplements have plenty of evidence backing their use individually.
Keep an eye out for more carnitine news. "Don't forget your carnitine" may just become one of the most important items on your heart-health recommendation list.
Natural Foods Merchandiser volume XXIV/number 11/p. 32, 36