Antioxidants – vitamins said to hunt oxygen-free radicals that trigger ageing and disease – are sold over the counter everywhere and added to food, beverages and face cream. But according to Weizmann Institute of Science Prof. Nava Dekel of the biological regulation department, scientists still lack a complete understanding of how they act.
New research on rodents by Dekel and her team, recently published in the Proceedings of the [US] National Academy of Sciences, has revealed a possible unexpected side effect of antioxidants – they might cause fertility problems in females.
Common antioxidants include vitamins C and E. These work by eliminating free radical molecules produced naturally in the body. Stress can cause these chemically active molecules to be overproduced; in large amounts, they damage cells indiscriminately. By neutralizing these potentially harmful substances, antioxidants can theoretically improve health and slow the aging process.
But when Dekel and her research team – including her former and present doctoral students Dr. Ketty Shkolnik and Ari Tadmor – applied antioxidants to the ovaries of female mice, the results were surprising– ovulation levels dropped significantly. That is, very few eggs were released to reach the site of fertilization, compared to untreated ovaries.
To understand what lies behind these initial findings, the team asked whether ovulation might rely on the very “harmful” oxygen radicals destroyed by antioxidants.
Further testing in mice showed that this is, indeed, the case. In one experiment, for instance, 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 produced in response to luteinizing hormone serve, in turn, as mediators for this physiological stimulus leading to ovulation.
Among other things, these results help fill in a picture that has begun to emerge of fertility and conception, in which it appears that these processes share a number of common mechanisms with inflammation. It makes sense, says Dekel, that substances that prevent inflammation in other parts of the body might also interfere with normal ovulation, thus more caution should be taken when administering such substances.
Much of Dekel’s research has focused on fertility; her previous results are already helping some women become pregnant.
Ironically, the new study has implications for those seeking the opposite effect. Dekel explains that “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 an effective means of birth control that could be safer than today’s hormone-based prevention.”