Despite showing promise in boosting male fertility, there is no evidence that antioxidant supplements improve women's chances of having a baby, according to a review of 28 studies.
At least 12 percent of women of childbearing age experience infertility, according to national estimates. That does not necessarily mean they will never be able to conceive, but they have been unable to do so after having unprotected sex consistently for one year, or for six months for those age 35 and up.
Women seeking treatment for infertility sometimes take dietary supplements and antioxidants -- vitamin C, vitamin E, melatonin, or combination supplements, among others -- in the hopes of boosting fertility. But the new Cochrane review, published Sunday, found little evidence supporting efficacy of the supplements.
"I don't think the results were surprising in the sense that there are no national organizations or guidelines that recommend routine use of antioxidant supplements for fertility," said Dr. Wendy Vitek, head of the fertility preservation program at the University of Rochester's Strong Fertility Center, who did not work on the new review.
"But I definitely have women ask me about supplements," Vitek said. "I think there are a lot of feelings of self-blame with infertility, and women are looking to gain some sense of being proactive and of potentially controlling a very uncontrollable situation."
Antioxidants, found in many fruits and vegetables, can also be taken in pill form. Antioxidants can help reduce oxidative stress, which occurs when free radicals damage cells and their ability to function. According to background provided in the Cochrane review, oxidative stress can be brought on by many of the same conditions that contribute to infertility, such as ovulatory disorders and endometriosis.
"It is thought that the free radical 'scavenging' effects of antioxidants would help to repair any oxidative stress occurring in the female reproductive process," lead researcher Marian Showell, with the University of Auckland's department of obstetrics and gynecology, told The Huffington Post. "This has not been disproven by this review. We just didn't have high enough quality evidence to prove or disprove it."
All told, the studies included in the review included more than 3,500 women who were attending fertility clinics.
An earlier Cochrane review, on which Showell was also lead researcher, found that antioxidant use by male partners in couples undergoing fertility treatment was linked to higher birth rates, although the researchers cautioned that placebo-controlled studies would need to confirm the finding. The theory is that antioxidants help improve sperm quality by reducing oxidative stress, which could have a big impact, given that 30 percent to 80 percent of cases of male infertility are due to such sperm-related problems caused by oxidative stress.
Resolve, the National Infertility Association, estimates that one-third of infertility cases are attributed to the female partner, one-third are attributed to the male and the remaining third are caused by some combination of both partners, or are simply unexplained.
"Oftentimes, patients latch on to something they heard made a difference for this person or that person," said Vitek, who said there may be some secondary gain from the placebo effect of taking antioxidant supplements. But in general, she counsels women who are undergoing fertility treatments to simply adopt as healthy a lifestyle as they can -- to exercise and eat well and attempt to manage their stress.
Although the new findings on the limited benefits of antioxidants are not necessarily surprising, they are slightly disappointing, she said.
"It would be nice if we had easier answers for women," Vitek said. "It would make everyone's lives easier if we could say, 'Here, take this supplement.'"