Zinc deficiency leads to reduced numbers of sperm and impotence in men.¹ The correlation between blood levels of zinc and sperm quality remains controversial. Infertile men have been reported to have lower levels of zinc in their semen, than do men with normal fertility.² Similarly, men with normal sperm density tend to have higher amounts of zinc in their semen, than do men with low sperm counts.³ However, other studies have found that a high concentration of zinc in the semen is related to decreased sperm motility in infertile men.^4,5 A few studies have shown that oral zinc supplementation improves both sperm count^6,7 motility,^6,9 and the physical characteristics of sperm in some groups of infertile men.¹⁰ For infertile men with low semen zinc levels, a preliminary trial found that zinc supplements (240 mg per day) increased sperm counts and possibly contributed to successful impregnation by 3 of the 11 men.¹¹ However, these studies all included small numbers of volunteers, and thus the impact of their conclusions is limited. In a controlled trial, 100 men with low sperm motility received either 57 mg of zinc twice daily or a placebo.¹² After three months, there was significant improvement in sperm quality, sperm count, sperm motility, and fertilizing capacity of the sperm. The ideal amount of supplemental zinc remains unknown, but some doctors recommend 30 mg two times per day. Long-term zinc supplementation requires 1–2 mg of copper per day to prevent copper deficiency.

Arginine, an amino acid found in many foods, is needed to produce sperm. Research, most of which is preliminary shows that several months of L-arginine supplementation increases sperm count, quality,^12,13,14 and fertility.^15,16 However, when the initial sperm count was extremely low (such as less than 10 million per ml), L-arginine supplementation produced little or no benefit.^17,18 While some pregnancies have been attributed to arginine supplementation in preliminary reports,¹⁹ no controlled research has confirmed these claims. For infertile men with sperm counts greater than 10 million per milliliter, many doctors recommend up to 4 grams of L-arginine per day for several months.

Asian ginseng may prove useful for male infertility. One preliminary study found that 4 grams of Asian ginseng per day for three months led to an improvement in sperm count and sperm motility.²⁰

L-carnitine is a substance made in the body and also found in supplements and some foods (such as meat). It appears to be necessary for normal functioning of sperm cells. In preliminary studies, supplementing with 3–4 grams per day for four months helped to normalize sperm motility in men with low sperm quality.^22,23 While the majority of clinical trials have used L-carnitine, one preliminary trial found that acetylcarnitine (4 grams per day) may also prove useful for treatment of male infertility caused by low quantities of immobile sperm.²⁴

A small clinical trial found that healthy men who took dried maca powder had increased sperm counts and enhanced sperm motility.²⁵

In a double-blind study of infertile men with reduced sperm motility, supplementation with selenium (100 mcg per day for three months) significantly increased sperm motility, but had no effect on sperm count. Eleven percent of 46 men receiving selenium achieved paternity, compared with none of 18 men receiving a placebo.²⁶

Vitamin B12 is needed to maintain fertility. Vitamin B12 injections have increased sperm counts for men with low numbers of sperm.²⁷ These results have been duplicated in double-blind research.²⁸ In one study, a group of infertile men were given oral vitamin B12 supplements (1,500 mcg per day of methylcobalamin) for 2 to 13 months. Approximately 60% of those taking the supplement experienced improved sperm counts.²⁹ However, controlled trials are needed to confirm these preliminary results. Men seeking vitamin B12 injections should consult a physician.

L-carnitine is a substance made in the body and also found in supplements and some foods (such as meat). It appears to be necessary for normal functioning of sperm cells. In preliminary studies, supplementing with 3–4 grams per day for four months helped to normalize sperm motility in men with low sperm quality.^30,31 While the majority of clinical trials have used L-carnitine, one preliminary trial found that acetylcarnitine (4 grams per day) may also prove useful for treatment of male infertility caused by low quantities of immobile sperm.³²

Coenzyme Q10 (CoQ10) is a nutrient used by the body in the production of energy. While its exact role in the formation of sperm is unknown, there is evidence that as little as 10 mg per day (over a two-week period) will increase sperm count and motility.³³ In one study, men with low sperm counts were given CoQ10 (60 mg per day for about three months). No significant change was noted in most sperm parameters, but a significant improvement was noted in in-vitro fertilization rates.³⁴

Preliminary research suggests that oral SAMe (S-adenosyl-L-methionine), in amounts of 800 mg per day, may also increase sperm activity in infertile men.³⁵

Vitamin E deficiency in animals leads to infertility.³⁶ In a preliminary human trial, 100–200 IU of vitamin E given daily to both partners of infertile couples led to a significant increase in fertility.³⁷ Vitamin E supplementation may enhance fertility by decreasing free-radical damage to sperm cells. In another preliminary study, men with low fertilization rates in previous attempts at in vitro fertilization were given 200 IU of vitamin E per day for three months.³⁸ After one month of supplementation, fertilization rates increased significantly, and the amount of oxidative stress on sperm cells decreased. However, the evidence in favor of vitamin E remains preliminary. A review of research on vitamin E for male infertility concluded that there is no justification for its use in treating this condition.³⁹ Controlled trials are needed to validate these promising preliminary findings.