Studies have shown that carnitine supplementation can help nerve degeneration in diabetics, assist with male infertility, possibly help sportsmen and women improve their performance, and even help to alleviate nerve damage caused by HIV drugs.
What is carnitine?
Carnitine is defined by Krause (2000) as, "A required cofactor derived from the essential amino acids methionine and lysine; carnitine facilitates transfer of long-chain fatty acids across the mitochondrial membrane for use as an energy source."
In other words, carnitine is a compound that is made in the human body from amino acids if the diet contains the so-called essential amino acids methionine and lysine.
These amino acids are mainly found in high-quality proteins such as meat, fish, eggs, milk and dairy products. Carnitine helps to transport long-chain fatty acids derived from fats into cells so that the fatty acids can be used for energy purposes.
Sources of carnitine
As mentioned above, carnitine is produced in the human body if the diet contains essential amino acids derived from foods such as meat, fish, eggs, milk and dairy products.
Foods derived from plants are usually not a good source of such essential amino acids, so that infants who are fed on non-supplemented soy-based formulas have low tissue levels of carnitine and may require supplementation.
People following a normal diet, which includes foods derived from animals, generally do not develop a carnitine deficiency.
However, preterm infants and infants fed soy-formulas that are not supplemented with carnitine, and patients undergoing dialysis or suffering from liver disease, may develop a carnitine deficiency.
Certain conditions such as diabetes or treatments (e.g. HIV/Aids drugs) may also increase the requirement for carnitine.
Carnitine and HIV/Aids
A recent study reported in the Arbor Clinical Nutrition Updates (Issue 213, 2005) found that carnitine supplementation (3 g/day) helped to prevent nerve damage caused by certain HIV drugs.
It has also been suggested that carnitine may be useful for treating the fat distribution syndrome or lipodystrophy that some patients receiving antiretroviral drugs may experience.
Carnitine and diabetes
Two trials conducted at 62 research centres in the USA and Europe indicated that the use of carnitine supplementation (500 to 1000 mg per day) in more than 1200 diabetics over a period of 12 months, significantly prevented nerve deterioration and decreased nerve pain (Arbor Clinical Nutrition Updates, Issue 212, 2005).
Carnitine and infertility
Two Italian studies investigated the effect of carnitine supplementation on sperm function and male infertility. In the first study, 170 infertile men were given 1 000 mg carnitine/day for six months. It was found that carnitine supplementation improved sperm concentration, count, motility and DNA integrity.
In the second random controlled study 56 infertile men were given up to 3 g of carnitine a day for six months. Significant improvements in sperm function were observed.
Researchers suggest that carnitine supplements may assist infertile men to improve their sperm count and function. Sperm mobility and viability appear to be influenced by carnitine levels and it has been proposed that carnitine supplementation can be considered as a treatment option in infertile men (Arbor Clinical Nutrition Updates, Issue 212, 2005).
Carnitine and sport
Many sport formulations nowadays contain carnitine. The manufactures claim that carnitine can improve cardiovascular function and muscle strength, delay fatigue and decrease muscle pain and body fat (Krause, 2000).
Few studies have been carried out to substantiate these claims and we don't know for sure if carnitine will really fulfil all these promises in sports nutrition.
Sportsmen and women tend to eat a great deal of protein derived from animals such as meat, milk, dairy products, and ergogenic formulations, so it is highly unlikely that the average sportsman or woman is deficient in carnitine.
The use of carnitine supplements in sport may not really be necessary, but hopefully additional research will eventually clarify if individuals who participate in strenuous sport require additional carnitine or not.
It has been suggested that carnitine may be 'conditionally essential', which means that in certain circumstances such as diabetes and male infertility, and in certain patients who take HIV/Aids drugs or have an increased requirement or an inadequate diet, carnitine supplementation may be necessary. – (Dr Ingrid van Heerden, DietDoc)
(References: Krause's Food, Nutrition & Diet Therapy (2000). Edited by Mahan & Escott-Stump, Chapter 4, p31; Arbor Clinical Nutrition Updates (2005) Issue 212, June; Arbor Clinical Nutrition Updates (2005) Issue 213, June.)