Walnuts have been linked to increased sperm strength in young men.
70 million couples worldwide experience sub-fertility or infertility. In fact, 30-50% 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.
Research published in the August 2012 issue of Biology of Reproduction 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.
 Anderson JE, Farr SL, Jamieson DJ, Warner L, Machaluso M. Infertility services reported by men in the United States: national survey data. FertilSteril. 2009;91:2466-2470.