Grazing on nuts may boost men’s fertility, according to doctors who found that a daily snack of almonds, hazelnuts and walnuts increased the number and quality of the sperm men produced.
Fertility specialists in Spain examined the sperm of 119 healthy young men before and after a 14-week study during which half were randomly assigned to have 60g of mixed nuts added to their diet each day.
At the end of the study, those who had received daily nut snacks had on average 16% higher sperm counts than those who went without, with more modest improvements seen in the proportion of living sperm, their shape and their swimming prowess.
The findings add to a growing body of evidence that diet has an impact on sperm and male fertility more generally. Other recent studies have linked improvements in sperm quality to diets rich in polyunsaturated fats such as omega-3, antioxidants including vitamins C and E, selenium and zinc, and folate, all of which are abundant in nuts.
“The results of our study could potentially help couples’ chances of conceiving,” said Albert Salas-Huetos, who led the study at the University Rovira and Virgili in Reus, Spain. “But I would not recommend anything based on only one study.”
Sperm counts in men have , a trend that has led to a raft of scientific investigations into the possible causes. Pollution, bad diets and general poor health have all been suggested as potential contributing factors.
Nicholas Macklon, medical director at London Women’s Clinic, said the research was one of a number of trials that could help doctors get to the bottom of what foods might have a genuine impact on sperm quality and potentially fertility.
“The changes are notable and likely to be beneficial for fertility,” Macklon said. But he cautioned that the impact might be limited because so many other factors contribute to fertility.
As well as improvements in sperm count and shape, the researchers examined the quality of DNA inside the sperm. They found that men in the nut group had sperm with less fragmented DNA. Sperm with highly fragmented DNA has been associated with male infertility.
Salas-Huetos presented the work at the annual meeting of the European Society of Human Reproduction and Embryology in Barcelona this week. The work, funded by the International Nut and Dried Food Council, has been accepted for publication in the American Journal of Clinical Nutrition.
“The fact that the study has taken place is good,” said Virginia Bolton, a consultant embryologist at Guy’s and St Thomas’s hospital in London, “but we need to see this translated into an effect on fertility.”