Eating nuts as part of a regular diet significantly improves the quality and function of human sperm, researchers in Spain have found.

During a 14-week randomized clinical trial, 119 healthy and apparently fertile men ages 18 to 35 were put into two groups. One followed their usual Western-style diet supplemented with 60 grams — roughly a half-cup — of mixed almonds, hazelnuts, and walnuts daily. The other group ate a Western-style diet without nuts, EurekaAlert reported.

Researchers measured conventional semen parameters and molecular changes, and found that the group that ate nuts had improvements in their sperm count, vitality, motility, and shape.

A Mediterranean diet included fruits, vegetables and fish.
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A Mediterranean diet included fruits, vegetables and fish.

Lead researcher Albert Salas-Huetos from the Human Nutrition Unit of Rovira i Virgili University in Reus, Spain, said the study was set against a background of general decline in the quantity and quality of sperm in industrialized countries due to "pollution, smoking, and trends toward a Western-style diet."

A Mediterranean diet is rich in fruits, fish, whole grains, legumes, and olive oil – and a splash of red wine. The Western-style diet includes red and processed meats, fried foods, high-fat dairy, eggs, butter, and sugary drinks.

A half-cup of mixed nuts can contain about 400 calories, according to Calorie King.

There are plenty of causes of problematic sperm production.

Medical causes could include swelling of the veins that drain the testicle, infections, tumors, celiac disease, or ejaculation problems. Overexposure to benzenes, toluene, herbicides, pesticides, organic solvents, painting materials, and lead might contribute to low sperm counts, and exposure to X-rays or other radiation might alter sperm production, according to the Mayo Clinic.

Even frequent use of saunas or hot tubs might temporarily impair sperm count.

And if you are thinking of washing down those nuts with a pint of beer, hold off. Alcohol can be a contributor to low sperm count. Drug use, tobacco, and obesity also play a role, the clinic reported.

Salas-Huetos said that the study results cannot be extrapolated to the general population. But they are consistent with results from other studies that included diets rich in omega-3, antioxidants such as Vitamins C and E, selenium, zinc, and folate, he said.

"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," Salas-Huetos said.