L-carnitine found to boost sperm quality and fertility

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I remember learning in medical school that one third of cases of infertility are exclusively down to the man, a third down to the woman, and a third were due to issues with both. If true, that means that two thirds of cases of infertility involve male infertility, which I think is a higher percentage than most people imagine (my experience is that individuals believe that infertility is much more often a female-based issue than a male one).

Male fertility issues come in a number of forms which include low sperm numbers, high numbers of abnormal sperms, and sperms that lack motility (asthenozoospermia). There is at least some evidence that nutritional supplementation can help improve male fertility by helping to resolve one or more of these issues.

I was interested to read about a recent Chinese study which assessed the effect of the nutritional agent L-carnitine on men with asthenozoospermia. Half the men in this study were treated with 2 grams of L-carnitine each day along with some vitamin E, while the other half took just vitamin E. The study lasted 3 months.

Those taking the L-carnitine saw the percentage of motile sperm rise from about 29 per cent to 45 per cent. Perhaps more importantly, rate of preganancy in this group was about 31 per cent, which compared very favourably with the 3.8 per cent seen in the group taking vitamin E only.

This is not the only study which suggests that L-carnitine has the capacity to improve sperm motility. In another study, 3 g of L-carnitine each day increased the proportion of sperm showing normal motility [2].

Other nutrients that have been tested and found to have promise for male fertility include vitamin C and zinc. Vitamin C appears to help prevent sperm from sticking together (something known as ‘agglutination’), and also increases the percentage of normal sperm [3].  500 mg of vitamin C should be taken, twice a day.  And in another study, zinc supplementation was shown to improve athenozoospermia [4].

Another thing that may help here is to avoid tight underwear. Sperm production is generally enhanced in cooler temperatures (that’s why the testes are containing in a sac outside the body). And long hot baths should perhaps be avoided too by men wanting to maximise their fertility.


1. Wang YX, et al. L-carnitine: safe and effective for asthenozoospermia. Nan Ke Xue, 2010;16(5): 420-2

2. Costa M, et al. L-carnitine in the idiopathic asthenozoospermia: a multicenter study. Andrologia 1994;26:155-159

3. Anonymous. Sperm swim singly after vitamin C therapy. JAMA 1983;249:2747-2751

4. Omu AE, et al. Indications of the mechanisms involved in improved sperm parameters by zinc therapy. Med Princ Practice 2008;17(2):108-16.

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