The study – published in Biology of Reproduction – investigates whether increasing polyunsaturated fatty acids (PUFAs), that are critical for sperm maturation and membrane function, would increase sperm quality in men consuming a Western-style diet.
Led by Dr Wendie Robbins at the University of California, Los Angeles, USA, the research team reveals that eating 75 grams of walnuts a day improves the vitality, motility, and morphology of sperm in healthy men aged 21 to 35.
“Improved semen quality was associated with increases in blood serum omega-6 FA and in the plant source of omega-3 (ALA) but not with other omega-3s,” reveal Robbins and her colleagues.
“Whether adding walnuts to the diet will go beyond the shifts in sperm parameters as seen in this study to improving birth outcomes for men within fertility clinic populations or in the general population is not yet known and will require further research,” they note.
The study, which was supported by the California Walnut Commission, assessed the quality of 117 healthy men between the ages of 21 and 35. Robbins and her team split the men into two groups, with 58 avoiding consumption of all tree nuts, whilst 59 consumed 75 grams of walnuts per day for 12 weeks.
Previous studies have indicated that 75 grams of walnuts is a consumption level at which blood lipid levels would change, but at which healthy young men would not gain weight, note the researchers.
The participants semen quality was analyzed according to conventional parameters of male fertility, including sperm concentration, vitality, motility, morphology, and chromosome abnormalities.
After 12 weeks, the team found no significant changes in body-mass index, body weight, or activity level in either group.
The men consuming walnuts, however, had significantly increased levels of omega-6 and omega-3 (ALA) fatty acids and experienced improvement in sperm vitality, motility, and morphology, explains Robbins and her colleagues.
Those eating walnuts also had fewer chromosomal abnormalities in their sperm following the dietary intervention. The control group, on the other hand, experienced no changes, they said.
Robbins noted that although her team’s research indicates that consumption of walnuts can positively affect sperm quality, it is still unknown whether such benefits would apply to men with fertility problems or whether they would actually translate into increased fertility.
Source: Biology of Reproduction
Published online ahead of print doi: 10.1095/biolreprod.112.101634
“Walnuts Improve Semen Quality in Men Consuming a Western-Style Diet: Randomized Control Dietary Intervention Trial”
Authors: Wendie A. Robbins, Lin Xun, Leah Z. FitzGerald, Samantha Esguerra, et al