Research published in the recent issue of Biology of Reproduction Papers-in-Press reports that 75 grams (approximately 2.5 ounces) 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 ~3.3 – 4.7 million.
This research suggests that walnuts provide key nutrients that may be essential in male reproductive health. According to Professor Wendie Robbins, Ph.D., R.N., F.A.A.N., who led the research at the University of California, Los Angeles, 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 Dr. Robbins thinks may work together synergistically. Co-investigator and UCLA Associate Professor of Medicine and Nursing Dr. Catherine Carpenter believes that "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."
Throughout history, food has been linked with human reproductive success; however most of the emphasis has been on the maternal diet and very little focus has been given to the paternal diet. According to Dr. Robbins, science is suggesting that a father's diet not only impacts fertility, but can also influence the health of the child and future generations. Citing a review of the science in this area, Dr. Robbins commented that, "diet is not just maternal territory anymore." It appears the nutrition status of fathers can be passed down transgenerationally and affect the health of generations to come. "Healthy diet and nutrition are essential for reproductive health," commented registered dietitian and father Milton Stokes. Based on this research, he would advise his male clients trying to have children to include walnuts in their diet on a daily basis to promote healthy offspring.
Improvements in cardiovascular risk factors and endothelial function from walnuts are well documented. The young men eating walnuts in the study conducted by Dr. Robbins experienced improved blood lipid profiles which reinforces these previous studies and provides one more reason to include walnuts in the daily diet.
This randomized, parallel two-group dietary intervention trial evaluated the effect of 75 grams 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 grams 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.