To have healthy babies, get your man in good health first. That's the conclusion of new research that says a dad-to-be's diet before conception can play a crucial part in the health of his future children.
Canadian scientists discovered that sperm carries a 'memory' of the father's lifestyle, and is transferred to their children following conception.
The scientists said: "You are what your father eats."
They advised men thinking about starting a family to lay off junk food and to eat green, leafy vegetables instead.
Researchers at McGill University in Montreal compared the health of mice born to fathers deficient in folic acid to that of mice sired by males with normal levels of the vitamin.
All of the mothers had normal levels of folic acid.
To the researcher's surprise, the mice born to males low in folic acid were almost 30 per cent more likely to have birth defects, including some severe deformities of the spine and skull.
A researcher said: "We were most taken aback by the increased incidence of birth defects.
"Lots of attention has been paid to a mother's health pre-conception yet the health of the father has been pretty much ignored.
"Because men have their fertility through their life, they think they are good to go at any time and the focus has been on women because they are the incubators of the pregnancy.
"But both men and women need to think about what they are doing pre-conception."
The study, published in the journal Nature Communications, suggests that lack of folic acid makes subtle changes to the chemistry of the sperm's DNA.
Good sources of folic acid include broccoli, Brussels sprouts, spinach, asparagus and peas, as well as liver, chickpeas and brown rice.