19 January 2011

Antioxidants causing fertility problems

by Kate Melville

Antioxidants are a popular dietary supplement but we still don't have a complete understanding of how they act in our bodies. Now, new research in the Proceedings of the National Academy of Sciences warns about a possible unexpected side effect of antioxidants: they may cause fertility problems in females.

Common antioxidants include vitamins C and E, which work by eliminating molecules called reactive oxygen species that are produced naturally in the body. Stress can cause these chemically active molecules to be overproduced and in large amounts they damage cells indiscriminately. By neutralizing these potentially harmful substances, antioxidants - theoretically - improve health and slow down the aging process.

But when Professor Nava Dekel of the Weizmann Institute applied antioxidants to the ovaries of female mice, the results were surprising: ovulation levels dropped precipitously. That is, very few eggs were released from the ovarian follicles to reach the site of fertilization, compared to those in untreated ovaries.

To understand what lies behind these initial findings, the researchers asked whether it was possible that the process of ovulation might rely on the "harmful" substances destroyed by antioxidants - reactive oxygen species.

Further testing in mice showed that this was the case. In one experiment, Dekel and her team treated some ovarian follicles with luteinizing hormone, the physiological trigger for ovulation, and others with hydrogen peroxide, a reactive oxygen species. The results showed hydrogen peroxide fully mimicked the effect of the ovulation-inducing hormone. This implies that reactive oxygen species that are produced in response to luteinizing hormone serve as mediators for the stimulus leading to ovulation.

Interestingly, these results add weight to the theory that fertility and conception share a number of common mechanisms with inflammation. It makes sense, says Dekel, that substances which prevent inflammation in other parts of the body might also get in the way of normal ovulation.

"On the one hand, these findings could prove useful to women who are having trouble getting pregnant. On the other, further studies might show that certain antioxidants might be effective means of birth control that could be safer than today's hormone-based prevention," observed Dekel. The researchers are now planning further studies to investigate the exact mechanics of this step in ovulation and to examine its effect on mice when administered in either food or drink. In addition, they plan to collect data on the possible link between females being administered antioxidant supplements and difficulty in conceiving.

Antioxidants found to impair muscle function
Antioxidant supplements found to induce genetic abnormalities
Scientists cast doubt on role of free radicals in aging

Source: Proceedings of the National Academy of Sciences