Experimental zinc deficiency in man: effect on spermatogenesis.

Dietary zinc intake was restricted (2.7-5.0 mg daily) for 24 to 40 weeks in five male volunteers. Their ages ranged from 51 to 65 years with a mean age of 57 years. Oligospermia was induced in all. In four subjects, oligospermia occurred 2 to 14 months after zinc restriction was instituted. In one subject, the onset of oligospermia was not accurately determined. The duration of oligospermia in the four subjects ranged from 6 to 14 months. Oligospermia was reversed after 2 to 32 months of zinc supplementation in physiologic amounts. The baseline sperm count (mean +/- SE) 289 +/- 85 millions/ml dropped to 33 +/- 4.5 millions/ml (P less than 0.05) following zinc restriction, and increased to 151 +/- 33 millions/ml after zinc supplementation (P less than 0.025). Oligospermia coincided with decline in Leydig cell function and was reversed in three subjects after zinc supplementation in low doses. Our study has demonstrated that dietary restriction of zinc can decrease sperm count, and that oligospermia induced by mild zinc deficiency is a reversible process. Oligospermia seems to be a sensitive indicator of zinc deficiency.