- Eating a walnut-enriched diet may improve sperm quality and reduce the damage to sperm cells.
- Walnuts contain polyunsaturated fatty acids and key nutrients that may be essential for sperm function in mice.
- As the study is done in animals, this has no inference on the effect of walnuts in adult men.
Lipid peroxidation is a process that can damage sperm cells. This form of cell damage harms sperm membranes, which are primarily made up of polyunsaturated fatty acids (PUFAs). New animal research suggests eating a walnut-enriched diet may improve sperm quality by reducing lipid peroxidation.
Walnuts are the only tree nut that are predominantly comprised of PUFAs (one ounce contains 13 grams of PUFAs out of 18 grams of total fat).
‘Sperm motility or movement and the form of sperms are markers of semen quality. Mice on a walnut-rich diet experienced improvement in sperm motility and form in 9 - 11 weeks.’
Research on the health benefits of PUFAs has advanced and most recently the 2015-2020 Dietary Guidelines for Americans has emphasized PUFA as a replacement for saturated fats.
As this is an animal study, there is no direct correlation to processes that occur in the human body. However, the findings support previous research suggesting that walnuts provide key nutrients that may be essential for sperm function.
Martin-DeLeon set out to understand the mechanism involved in improved sperm quality with a walnut-enriched diet. Healthy male mice as well as mice that were genetically predetermined to be infertile (Pmca4-/- gene deletion) were randomly assigned to a walnut-enriched diet or a control diet without walnuts that was followed for 9-11 weeks.
Among the mice that consumed walnuts, fertile mice experienced a significant improvement in sperm motility and morphology and the infertile mice had a significant improvement in sperm morphology. Both groups experienced a significant reduction in peroxidative damage. However, investigators were unable to reverse the adverse effects on sperm motility in the infertile mice because of the genetic deletion in this group.
"This animal research sheds light on how walnuts may improve sperm quality and is a great follow up to our human study that showed what effect walnuts may have," says Dr. Robbins. "Studies that look at the factors underlying sperm quality improvements are very valuable for advancing research on this important topic."
Walnut-enriched Diet Boosts Sperm Quality
Researchers found significant improvements in sperm motility and morphology in mice that consumed a diet containing 19.6% of calories from walnuts (equivalent to about 2.5 ounces per day in humans) compared to mice that did not consume walnuts. Sperm motility (movement) and morphology (form) are markers of semen quality, which is a predictor of male fertility.
"What's fascinating is we found that eating walnuts can actually help improve sperm quality, likely by reducing peroxidative damage in sperm cells," says lead researcher, Patricia A. Martin-DeLeon, PhD of 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."
Limitations of the Study
As with any research, study limitations should be considered. Animal research is provided as background and used to inform future studies needed to understand the effect on humans. Larger and longer-term studies, as well as studies in more diverse male populations, are needed to confirm the mechanism involved in improved sperm quality with a walnut-enriched diet. Additionally, the impact on birth outcomes is still unknown and will require more investigation.
Facts on Walnuts
- Walnuts are high in protein, vitamins, omega 3 fatty acids, trace minerals, lecithin and oils.
- Walnuts are unique as they are the only nut with a significant amount of alpha-linolenic acid.
- Walnut is a rich source of manganese, one serving contributing to almost half of its required daily value.
- Two or more servings of walnuts per week lower the risk of Type 2 diabetes by 15 to 21%.
- Lauren S. Coffua and Patricia A. Martin-DeLeon, Effectiveness of a walnut-enriched diet on murine sperm: involvement of reduced peroxidative damage, Heliyon (2017), http://dx.doi.org/10.1016/j.heliyon.2017.e00250 .