Growing evidence suggests that various forms of the supplement L-carnitine may improve sperm function and thereby aid male infertility .
For example, in one double-blind study, 60 men with abnormal sperm function were given either placebo or a mixture of two forms of carnitine (L-carnitine and acetyl-L-carnitine) for six months. The results showed significant improvement in sperm function in the treated group as compared to the placebo group. Another study found benefits with L-carnitine taken alone.
An article published in 2007 reviewed all the current evidence regarding carnitine therapy for male infertility. Its conclusion: L-carnitine, alone or in combination with acetyl-L-carnitine, may enhance sperm function and thereby improve male fertility.
For more information, including dosage and safety issues, see the full carnitine article.