The simple way to boosting male fertility, a major problem across the world, could be gobbling a handful of walnuts, researchers say.
"The initial research we conducted regarding walnuts and male fertility found improvement in sperm parameters after adding walnuts to the diet and has set the stage for us to further explore the impacts of walnuts on male fertility and reproductive health," Professor Wendie Robbins, University of California, Los Angeles (UCLA) School of Nursing.
"New projects are underway that we hope to be able to share with you in the near future," she said.
Infertility and subfertility affect a significant proportion of humanity and the burden in men is relatively unknown.
Infertility is defined as a "disease of the reproductive system" and results in disability.
Commenting on the study in 2012 by a team led by her, Robbins said that 75 grams of walnuts consumed daily improved sperm vitality, motility, and morphology (normal forms) in a group of healthy young men between 21-35 years of age.
These findings, published in the journal Biology of Reproduction, are of particular interest to the over 70 million couples worldwide who experience sub-fertility or infertility.
In fact, 30 to 50 per cent of these cases are attributed to the male partner, and in the US the prevalence of men seeking help for fertility is estimated at 3.3 4.7 million.
This research suggests that walnuts provide key nutrients that may be essential in male reproductive health.
According to Robbins, "the positive finding of walnuts on sperm may be a result of their unique nutrient profile."
Walnuts are the only nut that are an excellent source of alpha-linolenic acid (ALA) the plant-based omega-3 fatty acid.
The study also reported higher amounts of ALA provided by walnuts correlated with less frequent aneuploidy or abnormal cell sperm chromosome numbers which can result in genetic abnormalities such as Down syndrome, she said.
In addition to ALA, walnuts have high antioxidant content, along with numerous micronutrients that Robbins thinks may work together synergistically.
Food has been linked with human reproductive success but most of the emphasis has been on the maternal diet and very little focus has been given to the paternal diet, Carol Berg Sloan, Nutrition Consultant with the California Walnut Commission said.
She said the study by Robbins emphasises that a father’s diet not only impacts fertility, but can also influence the health of the child and future generations.
The study by UCLA researchers included 117 healthy young men who routinely eat a Western-style diet. Approximately half consumed the 75 grammes of walnuts per day for 12 weeks, while the remaining half served as the control group.
After 12 weeks, compared to the control group, the walnut group experienced improvement in sperm vitality, motility, and morphology key components in male fertility, Robbins said.