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Prenatal vitamins like folic acid are par for the course for many women who are thinking about becoming pregnant. But growing evidence suggests that folate may be important for healthy sperm, too. Is it time to offer supplements to men?

Folic acid is a synthetic version of the vitamin folate, which is known to play an important role in the healthy division of cells. Women who don鈥檛 get enough folate in the early stages of pregnancy are more likely to have babies with birth defects of the brain and spinal cord.

Because of this, women who are planning to get pregnant or are in the early stages of pregnancy are routinely advised to take folic acid supplements in places like the UK. In the US and Canada, folic acid has been added to foods like bread and cereal on a mandatory basis since the 1990s.

Folate for fathers

But mounting evidence suggests folate might be important for fathers-to-be, too. Research in mice and rats has shown that the amount of folate a male ingests before conception influences the pregnancy outcomes of the female mouse and the health of the offspring.

To look for effects in people, Nerea Mart铆n-Calvo at the University of Navarra in Spain and her colleagues looked at the pregnancy outcomes of 108 heterosexual couples undergoing fertility treatment at a hospital clinic in Boston in the US. All of the study participants were asked to fill out a detailed food questionnaire, so that the team could estimate how much dietary folate each person was getting.

The team assessed the outcomes of the 113 resulting pregnancies and births. After accounting for factors such as age, BMI and the mother鈥檚 folate intake, the group found that men who had more folate in their diets had babies with a longer gestational period, which is generally thought to be beneficial to health, up to a point. An increase in folate intake in men of 400 micrograms per day 鈥� 鈥� was associated with a 2.6-day longer gestation period.

Too much or too little

The study is small, but supports other research findings. When a team at the Erasmus University Medical Center in Rotterdam in the Netherlands assessed 511 pregnancies, they found that the . Too much or too little folate was linked to smaller babies, so there appears to be an optimum level, say the authors of the work, who published the study in February.

This is probably thanks to the role that folate plays in sperm cells in establishing the epigenome, a layer of markers that influence which genes are switched on or off. These epigenetic changes have recently been found to carry through multiple generations.

It is too soon to recommend folic acid supplements to men who are planning to start a family, says Sarah Kimmins at McGill University in Montreal, Canada.

鈥淲e know folate is important for cell division, and men make a million sperm with every heartbeat [鈥�] but we don鈥檛 know what the right amount is for men for optimal fertility and the optimal sperm epigenome,鈥� says Kimmins, who researches environmental impacts on men鈥檚 fertility and the health of their offspring.

Supplements for men?

Folic acid supplements might be useful in a country where the vitamin isn鈥檛 routinely added to food but might be overkill in places like the US and Canada, if men are already getting enough in their diets, for example. 鈥淭hat is something that policy makers need to focus on and is why studies like this are very important,鈥� says Kimmins.

It isn鈥檛 just folate: other aspects of a man鈥檚 diet and lifestyle can also affect his fertility and the health of an embryo. Most of the men who volunteered for Kimmins鈥檚 research in Canada have been found to have a vitamin D deficiency, for example, which seems to be linked to low sperm motility.

鈥淢en who are smoking, exposed to drugs or second-hand smoke or are obese, for example, will have epigenetic changes to their sperm that can be passed on,鈥� says Ranjith Ramasamy at the University of Miami. 鈥淔olate is just the tip of the iceberg.鈥�

Boys need to learn that their lifestyle can affect their fertility for the rest of their lives, says Kimmins. 鈥淢en aren鈥檛 getting those messages 鈥� they often think they are not part of the equation,鈥� she says. Health advice for parents-to-be need to target men too, not just women, she says.