Research published in Biology of Reproduction Papers-in-Press reported that 75 g (approximately 2.5-oz.) of walnuts consumed per day improved sperm vitality, motility and morphology (normal forms) in a group of healthy young men between 21-35 years of age. These findings are of particular interest to the 70 million couples worldwide who experience sub-fertility or infertility. In fact, 30 to 50 percent of these cases are attributed to the male partner, and in the United States the prevalence of men seeking help for fertility is estimated at approximately 3.3 to 4.7 million.
This research suggests that walnuts provide key nutrients that may be essential in male reproductive health. According to Professor Wendie Robbins, PhD, RN, FAAN, who led the research at the University of California, Los Angeles (UCLA), School of Nursing, “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—and this study 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.
In addition to ALA, walnuts have high antioxidant content, along with numerous micronutrients that Robbins thinks may work together synergistically. “These findings are not surprising when you look at the nutritious content of walnuts, however the results are amazing considering the impact they might have on men of all ages, including older men, and men with impaired fertility,” said Dr. Catherine Carpenter, co-investigator and UCLA associate professor of medicine and nursing.
The randomized, parallel two-group dietary intervention trial evaluated the effect of 75 g of walnuts/day on semen quality. The study included 117 healthy young men who routinely eat a Western-style diet. Approximately half consumed the 75 g 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.