Nut-rich diets produce a higher sperm count and more powerful swimmers, according to a new study.
Scientists made the claim after conducting a randomised trial which measured conventional semen parameters and molecular changes over 14 weeks.
The clinical trial found better sperm in the healthy young men aged 18-35 who supplemented their usual western-style diet with 60 grams/day of mixed almonds, hazelnuts and walnuts.
Researchers say the findings "support a beneficial role for chronic nut consumption in sperm quality" and reflect the value of further male-specific dietary recommendations.
The study was presented by Dr Albert Salas-Huetos from the Human Nutrition Unit of the Rovira i Virgili University in Spain.
Dr Albert Salas-Huetos said the study was performed amid a general decline in the quantity and quality of sperm that men are producing.
In industrialised countries this has been attributed to "pollution, smoking, and trends toward a western-style diet".
Random dietary assignments in the study found that subjects randomised to the nut group had significant improvements in their sperm.
The findings are consistent with improvements in other recent studies, reporting that diets rich in omega-3, antioxidants, and folate produce better sperm.
Nuts are dense foods containing many of these nutrients and other phytochemicals.
Although results from the randomised trial are statistically significant, with a high level of scientific evidence, Dr Salas-Huetos warned that results couldn't be extrapolated to the general population.
More from Science & Tech
Dr Salas-Huetos said he couldn't advise nut supplements for men attempting to conceive "based solely on the results of this study".
He added: "But evidence is accumulating in the literature 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."