Folic Acid Boosts Sperm

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Mar 21 2008 - 1:32pm

Folic acid may improve men's chances of fathering a child, The Guardian reports. Women have long been encouraged to take folic acid when trying for a baby, but a new study has found "a link between high levels of the nutrient in men's diets and the genetic quality of their sperm," the newspaper says.

The study behind the story is a small cross-sectional survey of 89 healthy, non-smoking male volunteers. It found a link between folic acid intake and the frequency of abnormalities in sperm cells. By virtue of its design, limited conclusions can be drawn from the study and the results may have arisen by chance. Randomised controlled trials are needed to explore this relationship properly.

Where did the story come from? Dr Suzanne Young and colleagues from the University of California, the Lawrence Livermore National Laboratory, and the Lawrence Berkeley National Laboratory carried out this research. The study was funded by the National Institutes of Health, the Environmental Protection Agency and the United States Department of Energy. It was published in Human Reproduction, a peer-reviewed medical journal.

What kind of scientific study was this? Healthy sperm should have one copy of each sex chromosome (X or Y). Aneuploidy means the sperm contains an abnormal number of chromosomes. About 1% to 4% of a healthy male's sperm have some type of abnormality of this kind. Why these abnormalities happen is poorly understood and the role of nutrition has not been explored.

In this small cross-sectional study, researchers contacted 97 volunteers who were healthy, non-smoking, current or retired employees of a university research laboratory. Participants were sent a questionnaire to collect information about their sociodemographic characteristics, medical and reproductive history, and lifestyle. The questionnaire also included a food frequency section that looked at the type and amount of foods eaten daily. Participants were also sent instructions for semen collection, a sterile container and a protective thermos to provide a sperm sample. To ensure completion and accuracy, participants were contacted by telephone and the food frequency question was completed within a week of providing the sperm sample.

The researchers analysed the sperm samples to determine whether they had any abnormalities. They looked for abnormalities associated with the genetic disorders Klinefelter's, triple X, XYY, Turner and Down's syndromes. Eighty-nine men were available for analysis after excluding those with low sperm counts or unusable food consumption data. The researchers used statistical methods to assess whether there was any relationship between the frequency of different types of abnormality (per 10,000 sperm) and low, moderate or high daily intake (from diet and through supplements) of different micronutrients (vitamin C, vitamin E, beta-carotene, folate and zinc). The researchers also took into account some factors that could also affect sperm health, e.g. disease history, body mass index, occupational history and use of tobacco, alcohol or caffeine, among other exposures.

What were the results of the study? The researchers found that several micronutrients were associated with a lower frequency of different abnormalities. High folic acid intake was associated with 19% fewer abnormalities (all types) than moderate intake and 20% fewer than men with a low micronutrient intake. There were also reductions in specific types of abnormality. For example, there were 26% fewer sperm with no sex chromosome in the high-intake group compared with the low-intake group. There were also 30% fewer sperm with two X chromosomes (associated with triple X syndrome) and abnormalities on chromosome 21 (associated with Down's syndrome) in the high-intake group compared with the moderate-intake group.

However, men in the low-intake folic acid group had fewer sperm with two X chromosomes (associated with triple X syndrome) and abnormalities on chromosome 21 (associated with Down's syndrome) than in the moderate-intake group. High total zinc intake reduced the frequency of two X chromosomes by about 50% compared with the moderate-intake group and 39% compared with the low-intake group. Zinc was not associated with lowering the risk of other abnormalities. Vitamin C and vitamin E had no association with sperm abnormalities, but high beta-carotene intake reduced YY abnormalities.

The researchers calculated that there was a reduction of 3.6% in the frequency of total abnormalities for every 100 microgram increase in daily total folate. When considering the different types of abnormalities separately, the magnitude of reduction was similar for two X chromosomes, no chromosomes and abnormality on chromosome 21.

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There was a reduction of 2.8% in sperm having two Y chromosomes for every 1,000 microgram increase in daily total beta-carotene.

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