The nutrients in nuts including omega-3 fatty acids, folic acid, antioxidants (Vitamin C, E, Zinc and Selenium) etc. are all thought to be responsible for these improvements.
The quality and function of their sperm-including changes on a molecular level-were measured at the start and end of a 14-week period. The decline has been linked to factors including pollution, smoking, and unhealthy aspects of the Western-style diet, the study authors said. The men were randomized into two groups, one continuing on their usual western-style diet with no nuts, and the other group supplementing that normal diet with 60 grams a day of an almond/hazelnut/walnut mix.
Infertility affects around 11 per cent of women and nine per cent of men of a reproductive age in the US.
The researchers, from the University Rovira i Virgil, Tarragona, Spain, analysed 119 healthy men aged between 18 and 35 for 14 weeks.
The findings, say the investigators, "support a beneficial role for chronic nut consumption in sperm quality" and reflect a research need for further male-specific dietary recommendations. "Nuts are important because they are a key food for healthier life", he told Newsweek, pointing to the Mediterranean diet as a good option.
Improvements in the former group were around 16 percent in sperm count, 4 percent in sperm vitality, 6 percent in sperm motility and 1 percent in morphology.
"These four parameters are all associated with male fertility".
Dr. Salas-Huetos pointed out that the results of the study can not necessarily be applied to the general population, considering that the male subjects were all healthy and fertile men who followed a western-style diet.
He said the subjects in the nut group also showed a "significant reduction" in their levels of sperm DNA fragmentation, a parameter closely associated with male infertility. Not yet, said Salas-Huetos. For the analysis, the researchers recorded not only the quality of the sperm but also the changes that occurred in several molecular factors, including sperm DNA fragmentation. The work, funded by the International Nut and Dried Food Council, has been accepted for publication in the American Journal of Clinical Nutrition.