By Kathryn Doyle
NEW YORK (Reuters Health) - For women who struggle to conceive, there is little evidence that antioxidant supplements increase their chances, according to a new review.
Some women take the products, which include vitamins like C and E, minerals and polyunsaturated fatty acids in the hope they will help counteract disorders hampering fertility.
"I wouldn't say that women should not take antioxidants," only that there is no good evidence that antioxidants will help, said lead author Marian Showell of the department of Obstetrics and Gynecology at the University of Auckland in New Zealand.
Her team also found no evidence of harm from the antioxidants, Showell told Reuters Health by email.
From all of the literature on antioxidants and fertility, Showell and her coauthors reviewed the 28 best randomized controlled trials, involving a total of 3,500 women who were subfertile, meaning they were less fertile than average but still able to conceive.
Subfertility may result from ovulation problems, poor egg quality, fallopian tube damage and endometriosis, according to the report. Antioxidants are thought to reduce the oxidative stress, which damages cells and tissues, brought on by these conditions.
The trials assessed many types of oral antioxidants and anti-inflammatory supplements and drugs, alone and in combination. They included vitamins C, E and D plus calcium, as well as omega 3 fatty acids, melatonin, L-arginine, myo-inositol and pentoxifylline - a prescription drug sometimes used to treat endometriosis.
All the trials compared women taking the products to women given a placebo or no fertility treatment at all.
Women who took antioxidants were not more likely to become pregnant or to give birth to live babies according to the results published in The Cochrane Library.
"There are two main reasons why women have difficulty conceiving," said Cindy Farquhar, the coordinating editor for the Cochrane Menstrual Disorders and Subfertility Group but not an author of the new review.
"For ovulation problems, antioxidants could help, I guess, but there are no studies suggesting benefit," Farquhar told Reuters Health. "For blocked fallopian tubes, antioxidants would not help."
For unexplained infertility, without knowing the reason for the infertility there's no reason to believe antioxidants would help, she said.
According to the Centers for Disease Control and Prevention, 6.7 million U.S. women ages 15 to 44 have impaired fertility.
About 20 to 30 percent of women take supplements while trying to conceive, Farquhar said.
Showell published a Cochrane review in 2011 that did find evidence antioxidants may help improve male fertility.
She wasn't surprised to find a different result for women, though, since male fertility is mostly affected by oxidative stress, whereas female fertility is more complex and has more factors to consider, she said.
Oxidative stress is thought to damage sperm, so antioxidants may improve sperm quality, she said. Semen itself naturally includes antioxidants, Farquhar noted.
For women struggling to conceive, doctors might recommend eating a balanced diet, sleeping well, maintaining a healthy weight and not smoking, Showell said.
Antioxidants in food might have more of an effect than those in supplement form, she added, but there is a similar lack of evidence in that area.
Women who eat foods high in antioxidants are likely healthier in other ways too, like not smoking and maintaining a healthy weight, so it may be difficult to determine the specific role of vitamins and minerals, she said.
SOURCE: http://bit.ly/15F5G7u The Cochrane Library, online August 5, 2013.