All that attention might leave fathers-to-be feeling left out. But now, doctors say there may be something new that prospective dads can do to improve the reproductive process: Get more folic acid in their diet.
In a study published in the February issue of the journal Fertility and Sterility, researchers from the University of California at Berkeley and the U.S. Department of Agriculture's Western Human Nutrition Research Center link low levels of folic acid with low sperm counts and density.
It has been well established that women who take folic acid before and during pregnancy significantly reduce their risk of having a baby with neural tube defects such as spina bifida. Women are advised to get 400 micrograms of folic acid per day, either from dietary sources such as leafy greens, orange juice, legumes, and fortified cereals, or through vitamin supplements.
The study in men measured concentrations of folic acid, a type of vitamin B, in the blood and semen of 48 subjects who were 20 to 50 years old.
Folic acid is metabolized into different forms in the body. It was the low level of a certain type -- the non-methyl form -- that correlated with low sperm quality, the researchers found.
"One of folic acid's major roles is to participate in DNA synthesis," says lead author Lynn Wallock, PhD, a nutritionist and an assistant research scientist at the Children's Hospital of Oakland Research Institute. Wallock was working at the Western Human Nutrition Research Center at the time of the study.
The authors say the non-methyl form of folic acid is important in the production of thymine, one of the four nucleic acids used to make DNA. They also refer to a 1997 study published in the Proceedings of the National Academy of Sciences (a journal that publishes papers written by academy members) that linked deficiencies in folic acid to subsequent chromosome breaks.
"This confirms previous studies in rats, showing that folate deficiency, if it's severe, causes impairment in sperm counts," says Marc Goldstein, MD, an expert in male infertility who is not associated with the study. Goldstein, a professor of reproductive medicine and urology at Weill Medical College of Cornell University, and co-executive director of the Cornell Institute for Reproductive Medicine, says there is growing evidence that "folate does seem to be important in sperm production."
While Wallock and her colleagues also noted that smokers -- who made up approximately half the subject group -- had significantly lower levels of the non-methyl form in their semen than non-smokers, they drew no specific conclusions from this, calling instead for further research into this finding.
Based on Wallock's findings, men trying to conceive might benefit from the same daily dose of folic acid recommended for women. "Five to nine servings of fruits and vegetables a day should be adequate to meet folic acid requirements," says Wallock. Folic acid also may be obtained through supplements, but Wallock recommends improving the overall diet for the other important health benefits it imparts.
Goldstein says there's no harm in advising men to take a multivitamin, but he says there is no firm evidence that increasing folic acid in the diet will lead to higher sperm counts or higher fertility rates. He also says Wallock's study is limited by its small size and design. "The study is deficient in that it did not look at a general population," he tells WebMD. He notes that the men in the study reported eating no more than 3.5 servings of fruits and vegetables per day. "These are patients who are already likely to have folate deficiencies and inadequate folate nutrition."
Wallock agrees that it will be necessary to repeat the study with a larger group of subjects. Still, she says the study "probably reflects a large segment of the population. Many men out there don't eat many fruits and vegetables every day. ... We certainly don't have an extremely well-nourished population out there."
Other physicians emphasize the importance of looking at various nutrients and environmental factors, noting the complexity of male infertility.
The biochemistry of semen "is so complex," says Ronald Burmeister, MD, an infertility specialist at the Reproductive Health and Fertility Center in Rockford, Ill. "... I think folic acid is just one aspect of it."
Deficiencies in the nutrient zinc, for instance, also have been linked to decreased sperm production, according to a review article appearing in the March 2000 issue of Fertility and Sterility. Low levels of zinc, found naturally in meat, liver, eggs, and seafood, may interfere with the absorption and metabolism of folic acid.
Add alcohol to the mix and the picture becomes even more complicated. "Alcoholics tend to have lower zinc levels, which can then interfere with folate levels," says Rebecca Sokol, MD, professor of medicine and ob/gyn in the division of reproductive endocrinology and infertility at the University of Southern California Keck School of Medicine. Sokol will give a speech about nutrition and alternative therapies in male infertility at an upcoming meeting of the Society of Reproductive Medicine in Florida and expressed particular interested in the Wallock study.
Despite its weaknesses, the folic acid study does shine an important spotlight on male reproductive health, the researchers say. Goldstein says that roughly a third of all infertility problems are associated with females, a third with males, and a third with a combination of the two. It therefore makes sense to understand the male part of the infertility equation more thoroughly.
Furthermore, understanding nutritional factors in reproductive health would be particularly helpful since changing dietary habits is "easier than surgery," says Goldstein.
However, research into male reproductive health to date has been "absolutely neglected," says Philip Werthman, MD, urologist and director of the Center for Male Reproductive Medicine in Los Angeles. "Fertility [research] is driven by gynecologists ... and you rarely see gynecologists who want to treat the male partner."
"I certainly think [our study] justifies further research, not only in folic acid and sperm but other nutrients as well," Wallock tells WebMD. When it comes to looking at the potential impact of diet on male reproductive health, she says, "we've just scratched the surface."
Sarah Yang is a freelance writer in El Cerrito, Calif., who has written for The Los Angeles Times and The San Francisco Examiner. She is a frequent contributor to WebMD.