Men and Women May Need Different Diets

(July 17, 2008) - If you go to dinner with a member of the opposite sex, you might want to order something different from them. Diet can strongly influence how long you live and your reproductive success, but now scientists have discovered that what works for males can be very different for females. (Read about "Dietary Guidelines")

In the evolutionary "battle of the sexes," traits that benefit males are costly when expressed in females and vice versa. This conflict may have implications for human diet, aging and reproduction, say researchers.

"When it comes to choosing the right diet, we need to look more closely to the individual, their sex and their reproductive stage in life," says Rob Brooks, one of the researchers. "It may be, for example, that women in their child-bearing years need a different diet to those who are post-menopausal.

"It also underlines the important lesson that what we want to eat or, if you like, what we're programmed to eat, is not necessarily best for us." The researchers are conducting long-term studies on Australian black field crickets and have discovered that the lifespan of both males and females is maximized on high-carbohydrate, low-protein diets, they say in the latest issue of Current Biology.

But reproductive success differs dramatically between the sexes when the carbohydrate-protein balance is changed: males live longest and have the greatest reproductive success with a diet that favors carbohydrates to protein by eight-to-one, whereas females have greatest success when the ratio is just one-to-one. Given a choice, however, females eat only a small amount more protein than males. The shared ability to sense and choose food dooms both males and females to eat a diet that is a compromise between what is best for each sex.

"Men and women invest differently in reproduction, a difference that is even more marked than that between male and female crickets," says Brooks. "Think of the tremendous amounts of energy and protein required of a mother in carrying a baby to term and breastfeeding. (Read about "Healthy Pregnancy" "Breastfeeding") We also know that men and women need to eat different diets - think of the careful attention we pay to what expectant mothers eat.

"What men and women need to eat might be more dramatically different than we had realized. However, men and women eat very similar diets and our results suggest that our tastes and food preferences could be a shared compromise, as they are in crickets."