In contrast, a second study in men diagnosed with fertility problems suggests that daily antioxidant supplements have no beneficial effect on sperm health – contrary to the findings of previous work.
The studies were presented at the European Society of Human Reproduction and Embryology (ESHRE) conference in Barcelona, Spain, last week.
Snacking daily on a mix of almonds, hazelnuts and walnuts alongside a general Western-style diet lead to a 16 percent increase in sperm count, as well as improved sperm vitality, motility and morphology, revealed Dr Albert Salas-Huetos from the Universitat Rovira i Virgil in Reus, Spain.
He said it was too early to say that men trying for a baby should add nuts to their diets. 'But evidence is accumulating… that healthy lifestyle changes such as following a healthy dietary pattern might help conception – and, of course, nuts are a key component of a Mediterranean healthy diet,' he said.
Nuts are a natural source of nutrients including zinc, selenium, omega-3 and folate, which have been shown by previous studies to improve sperm health.
Dr Albert Salas-Huetos and colleagues randomised 119 healthy men, aged 18-35, to eat their usual diets either with or without a 60 gram daily supplement of mixed nuts for 14 weeks. The nut group not only showed improvement in the sperm parameters associated with fertility, but they also showed reduced levels of sperm DNA fragmentation – associated with male infertility.
Dr Salas-Huetos pointed out that the study was conducted in a healthy male population and therefore the results could not necessarily be extrapolated to the general population. The research was funded by the International Nut and Dried Food Council.
Professor Allan Pacey at the University of Sheffield, who was not involved in the research, said the strength of the study was its randomised, controlled design. However, he noted that it was not 'blinded'.
'It strikes me that if you were randomised to the nut eating arm, and were given nuts, that you would know that,' he said. 'There are many confounding factors that could have crept into the equation, such as the men in the nut eating arm knowing that and changing other aspects of their life as well.'
The second study found that giving the man in 174 couples a daily antioxidant supplement made no difference to sperm concentration, motility or morphology, nor to DNA fragmentation after three months. All the men in the US trial had had a diagnosis of male factor infertility.
The study authors said that previous work showing that antioxidants could benefit sperm quality were limited by small numbers and diverse patient groups, among other factors.
'The results do not support the empiric use of antioxidant therapy for male factor infertility in couples trying to conceive naturally,' said study author Professer Anne Steiner at the University of North Carolina in Chapel Hill.