Women are advised to get sufficient amounts of vitamin B9, or folate — found in green leafy vegetables, cereals, fruit and meats — to prevent miscarriages or birth defects in their babies.
But the way that a father's diet can influence the health and development of offspring has received little attention, said Sarah Kimmins, a specialist in reproductive biology at McGill University who led a study looking at the effects of paternal folate levels.
"It can't all be on the mother," Kimmins said Tuesday from Montreal. "Our study and others are now showing that the father can be a route for the transmission of birth defects and can influence offspring health."
"Guys need to pay attention to what they're doing in terms of lifestyle choices prior to having a baby, just like the woman does."
In a study of mice published in the journal Nature Communications, researchers found that a low-folate diet in males was linked to an increased rate of birth defects among their pups, compared to the rate among pups whose fathers were fed a folate-sufficient diet.
"When we looked at the offspring, when we looked at the fetuses, we were really quite shocked that we saw the birth defects," Kimmins said Tuesday from Montreal.
"We had increased changes in the pregnancy rate, and we expected that we would affect fertility, but we didn't expect that we would have these paternal-driven birth defects in response to a folate-deficient diet."
The birth anomalies, which occurred across the litters sired by folate-deficient mice, included spinal malformations, cranio-facial defects such as a shortened jaw, underdeveloped digits and club feet.
"Those were the types of things we saw as a consequence of that diet," Kimmins said. "So they're quite striking birth defects."
In humans, about three per cent of children are born with a birth defect of some kind, and the cause is known for only about half of them, she said.
In the mouse litters born to fathers with inadequate dietary folate, about four per cent of the pups had a birth anomaly.
"We were very surprised to see that there was an almost 30 per cent increase in birth defects in the litters sired by fathers whose levels of folates were insufficient," compared with those from sires fed folate-rich diets, said co-author Romain Lambrot, a post-doctoral fellow in McGill's department of animal science.
"We saw some pretty severe skeletal abnormalities."
While folic acid is added to a variety of foods, men who eat high-fat, fast-food diets or who are overweight or obese may not be able to efficiently metabolize B9, said Kimmins, noting that a lack of folate can affect their sperm.
"People who live in the Canadian North or in other parts of the world where there is food insecurity may also be particularly at risk for folate deficiency," she said. "And we now know that this information will be passed on from the father to the embryo with consequences that may be quite serious."
The researchers say a man's sperm carries a memory of his environment and possibly even his diet and other lifestyle choices through the epigenome, a network of chemical compounds surrounding DNA.
The epigenome, which is affected by environmental cues, is like a switch that influences how genes are turned on or off and how genetic information is passed from parents to children.
"I wouldn't go so far as to tell guys you need to start taking a folate supplement because we don't know what the right dose is, we don't know how it affects the human sperm genome," said Kimmins. "But I think we can say let's start paying attention to a male's preconception health."
"Look at things in your life like smoking, drinking, what you're eating and be aware that if you're living a bad lifestyle, you might transmit some of that information to your offspring."
The researchers' next step will be working with a fertility clinic to assess the links between a man's diet and the health of their children.