Antioxidant supplements 'unlikely' to improve fertility

05 August 2013

Taking an antioxidant supplement is unlikely to improve the chances of conception among women who undergo fertility treatment, a review has found.

Figures show that up to a quarter of all couples who are trying to conceive have difficulty, meaning they have been trying to conceive for more than a year without success, and the prevalence of so-called 'subfertility' has increased over the last couple of decades.

Research suggests that in 40 to 50 per cent of affected couples, the problem lies with the female, with common causes including ovulatory disorders, poor egg quality, fallopian tube damage or endometriosis.

Many women in this situation take antioxidant supplements in the belief that this will reduce the oxidative stress caused by these conditions and thus improve fertility.

However, the evidence in favour of antioxidant supplementation in women undergoing fertility treatment is unclear, so scientists at the University of Auckland in New Zealand conducted a review of published research.

The research team searched a number of databases in order to identify randomised controlled trials that had compared oral antioxidant supplements with placebo (dummy supplement), no treatment, standard treatment or a different antioxidant in sub-fertile women.

A total of 28 trials and 3,548 female participants were included in the review, which looked at a number of different antioxidants, including pentoxifylline, N-acetyl-cysteine, melatonin, L-arginine, vitamin E, myo-inositol, vitamin C, vitamin D with calcium, omega-3 polyunsaturated fatty acids and combinations of antioxidants.

Analysis revealed that antioxidants were no more likely to improve the rate of live births than a placebo, no treatment or standard care. Antioxidants were also not associated with increased pregnancy rates.

Fourteen of the trials reported adverse events, such as miscarriage, multiple pregnancies, ectopic pregnancies and gastrointestinal effects.

There was no evidence to suggest any difference in rates of adverse events between antioxidant supplement users and non-users. However, the researchers noted that information on this was "limited".

Overall, the researchers described the quality of evidence as "very low", both in studies that compared antioxidants versus a placebo or no treatment and in those that compared individual antioxidants against each other.

Publishing their findings in the Cochrane Library of reviews, they confirmed: "Antioxidants were not associated with an increased live birth rate or clinical pregnancy rate."

The study authors noted that there was some evidence of a link between a specific antioxidant called pentoxifylline and an increased clinical pregnancy rate. However, only three trials had looked at this association and future studies could achieve different results.

They also observed that variation in the types of antioxidants given to study participants "meant that we could not assess whether one antioxidant was better than another", and that data on the likelihood of adverse effects among supplement users were "limited".

Lead researcher Dr Marian Showell, who works in obstetrics and gynaecology at the University of Auckland, concluded: "There is no evidence in this review that suggests taking an antioxidant is beneficial for women who are trying to conceive."

Posted by Edward Bartel


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