US researchers commented on walnuts’ benefits to sperm quality suggesting oxidative stress as a primary mechanism underlying male reproductive defects.
"What's fascinating is we found that eating walnuts can actually help improve sperm quality, likely by reducing peroxidative damage in sperm cells," said lead study author Dr Patricia Martin-DeLeon, professor of Biological Sciences at the University of Delaware.
"More research is needed to understand the specific nutrients in walnuts that may contribute to this improvement, but the findings suggest that walnuts may be beneficial for sperm health."
Western diet effects
While these results were obtained from animals, there was no direct correlation to processes that occur in the human body.
However, the findings mirror a body of evidence that point to the walnut’s nutritional composition as essential in maintaining sperm quality and motility.
A published randomised control trial showed that eating 75 grams of walnuts per day improved sperm vitality, motility and morphology in men compared to men who did not add walnuts.
A Western-style diet has been accused of lowering sperm function, especially motility, vitality and morphology in both humans and animals.
A diet high in processed food, sugar and refined grain has been shown to play a major role in obesity and DNA damage in male germ cells; reducing rates of fertilisation and impacting on the health of the foetus and offspring.
Healthy and infertile male mice were randomly given a walnut-enriched diet or a control diet without walnuts for 9-11 weeks.
The healthy mice showed significant improvement in sperm motility and morphology whilst the infertile mice also showed improvement in sperm morphology.
Both groups experienced a significant reduction in peroxidative damage - the process that affects lipids in cell membranes, resulting in cell damage.
Despite these findings, researchers could not reverse the positive effects on sperm motility in the infertile mice because of their specific genetic make-up.
“A walnut supplement may function to reduce elevated levels of oxidative stress associated with abnormal sperm morphology,” the study said.
“The diet significantly improved only morphology, suggesting that different contributing factors may be involved in the motility and morphological defects.”
Previous walnut work
Previous work has shown the importance of fatty acid profile changes in sperm maturation and differentiation.
In addition, a positive relationship has been established between Omega-3 from the diet and normal sperm morphology in humans.
The researchers suggested that a walnut supplement, enriched in PUFAs and antioxidants might function to benefit specific sperm which have a loss of progressive and hyperactivated sperm motility.
Sperm morphology defects have also been linked with increased ROS and oxidative stress in murine sperm as well as DNA damage, although the exact mechanism is unclear.
“The significantly increased rates of normal morphology in WT sperm with administration of the walnut supplement suggests that the diet may have the ability to restore damage inflicted by oxidative stress,” the study added.
Published online ahead of print: doi.org/10.1016/j.heliyon.2017.e00250
“Effectiveness of a walnut-enriched diet on murine sperm: involvement of reduced peroxidative damage.”
Authors: Lauren Coffua, Patricia Martin-DeLeon