Fifteen of every hundred couples in the world who want to have children find it difficult or impossible to conceive. In about half those couples, the difficulty results from the male partner’s fertility. Now researchers at UNC Nutrition Research Institute (NRI), in Kannapolis, NC, have found a possible genetic cause for some incidences of male infertility.

A study led by NRI Director Steven H. Zeisel, M.D., Ph.D., has found that a very common genetic variant, called a single nucleotide polymorphism (SNP), is associated with decreased human sperm motility. The SNP is found within the gene CHDH (choline dehydrogenase) and can influence how straight a sperm can swim. Sperm must swim a long distance to fertilize an egg, and those that swim in circles are not effective. An estimated five and ten percent of men have this SNP. Mice with a defect in the gene CHDH also have sperm that don’t swim and are infertile, and feeding them supplemental betaine improves sperm function. Perhaps men with SNP in CHDH will also improve when treated with betaine.

The findings were published in the April 27, 2012 journal Public Library of Science (PLoS) One. “The study is exciting,” Zeisel said, “because this is the first time we realized that this nutritional pathway is important for sperm function, and we may have a nutrition-based solution form many men with infertility.”

Future clinical studies at the UNC NRI will explore whether nutrient supplements can improve sperm function in men with CHDH.