In America, about one in seven couples have difficulty conceiving a child and around 40 percent of the time it's because of the male.
But a new study from the University of California Los Angeles offers some hope. Researchers found that eating a handful of walnuts every day can substantially improve a man's fertility.
"We found that walnuts were beneficial to male reproductive health in that they significantly increased sperm vitality, sperm motility and sperm morphology, the shape of sperm," explained Prof. Wendie Robbins of the UCLA School of Nursing. "All of these are important indicators of male reproductive health."
The study looked at 117 healthy, young men. Half of the participants ate 75 grams of raw walnuts a day, and according to researchers, were much more fertile after three months.
"I think it's very important. Eventually I want to have a family," study participant Brandon Holiwell said. "I think this is something i'll definitely share with my family members, friends and family, that could be useful... I think it's definitely a breakthrough in men's health."
It's unusual for scientists to study nutrition in relation to male fertility and before now, any kind of male reproductive study was rare.
"I think we need to start focusing on the importance of male health as well as female health in terms of pregnancy and healthy offspring," Dr. Catherine Carpenter of the UCLA School of Nursing and Medicine told CBN News.
Eating walnuts isn't just a good idea for men wanting to have children, the nuts are considered a "super food" and a smart snack for everyone.
Walnuts are loaded with important omega-3 fats, antioxidants, protein and fiber.