Antioxidant supplements do not improve men's fertility

Use of antioxidant supplements by men does not improve pregnancy rates, according to a large-scale study by researchers in the Netherlands.

Over-the-counter antioxidant supplements have been widely marketed as improving male fertility. However, existing studies into their effectiveness have relied on small sample sizes and produced conflicting results. The new study, known as the SUMMER trial, included 1171 men aged 18-50, with female partners aged 18-43, who sought fertility care across 21 hospitals and fertility clinics in the Netherlands. The men were randomly assigned either the daily antioxidant supplement Impryl, containing nutrients such as betaine, zinc, folic acid and B vitamins, or a placebo. After six months, researchers found no significant difference in the pregnancy rates between the two groups.

'This randomised clinical trial found that ongoing pregnancy rates did not improve with the antioxidant supplement compared with a placebo. Therefore, the investigators do not support its use in men seeking fertility care,' the authors concluded in their paper, published in JAMA Network Open.

All couples participating in the trial either had no assisted reproduction treatment, intrauterine insemination (IUI), IVF, or IVF with intracytoplasmic sperm injection (ICSI). The results also showed no significant difference in sperm quality, sperm DNA fragmentation, embryo transfer rates after IVF or ICSI, or miscarriage risk, between the two groups.

The authors reported that their results were consistent with a previous US trial, published in JAMA, which included over 2000 couples. They wrote: 'Our findings are consistent with those of a large randomised trial in men seeking fertility care, which showed no benefit of treatment with folic acid and zinc to pregnancy outcomes within six months.'

The SUMMER trial results also showed that taking antioxidant supplements may in fact lower pregnancy rates. Within the expected window that treatment should be the most effective (four to six months), the pregnancy rate was lower in the antioxidant group (16 percent) than in the placebo group (22 percent).

'To our knowledge, our trial was the first to observe a significantly lower ongoing pregnancy rate within the optimal treatment window of 4 to 6 months,' the authors wrote.

The study concluded that the use of antioxidant supplements in male fertility care is not supported. Instead, the authors emphasised that standard fertility treatments, such as IUI, IVF, and ICSI, remain the main evidence-based options for couples struggling to conceive.