The controversial efficacy of vitamin E for human male infertility.

Vitamin E (VE) is major lipophilic chain-breaking antioxidant which protects tissue polyunsaturated fatty acids (PUFA) against peroxidation, a property that could be beneficial in the male reproductive physiology because the membranes of germ cells and spermatozoa are very sensitive to oxidation because of their high content of PUFA. Some of the available data on the efficacy of VE as an oral drug for male infertility or as an additive during in vitro manipulations of spermatozoa were reviewed here, observing that they are often contradictory, possibly because: (1) antioxidant therapy could be ineffective in certain studies not concentrated on men in whom oxidative stress is implicated as an infertility factor, and (2) the VE antioxidant therapy is a double-edged sword strictly depending on the dosage or the in vitro concentration of the vitamin. Thus, further laboratory and clinical studies with better-defined experimental conditions should be performed to establish the in vitro and in vivo efficacy of VE for human male infertility.