Protein, carb diets hold secret to fertility and long life

YOU can have kids or you can have a long life — and how rich your diet is in protein and carbs is crucial to success in both endeavours, a new study shows.

To run alongside the Weekend book extract on midwives.

YOU can have kids or you can have a long life and how much protein and carbohydrate you eat is crucial to success in both endeavours, a new study shows.

If you want to live a long life then carbohydrates are your friend.

However, if you want to have children you need protein to grow a large uterus and produce eggs and sperm, research in both mice and fruit flies at the University of Sydney shows.

“You can have sex or a long life but not both,” University Sydney researcher Professor David Le Couteur concludes.

Strategy ... the diet you need to get pregnant is different to the diet you need for a long life. Picture Thinkstock.

Fat wars have dominated recent diet debates but this research has found it is not important to the goal of reproduction or longevity unless you eat too much.

CARB WARS: Controversial high-fat diet questioned

And the best news is the research questions other studies that found the best way to ensure a long life was to cut energy intake by 25 per cent below recommended daily intakes.

“The balance of micronutrients, rather than total calorie intake, is a key nutritional factor that influences lifespan and reproduction,” the study published in the journal of the Proceedings of the National Academy of Science shows.

Key to fertility ... a high-protein diet can help produce eggs and sperm.

And it turns out the diet secrets to reproduction and longevity are different for males and females.

Males need more protein than females to reproduce and they need more carbohydrates than females to live long lives.

Researchers trialled 25 diets with varying proportions on protein, carbohydrates, fat and energy on mice to determine their effect on reproduction and longevity.

It found reproductive cycles were greatest in mice eating a diet with a protein to carbohydrate ratio of 1 to 8.

Bulking up ... carbohydrates can increase longevity.

Males had larger testes and produced more sperm on diets where the ratio of protein to carbohydrate was one to one.

This was exactly the same ratio of protein to carbohydrate other studies in fruit flies found optimal for reproduction.

However, the mice who lived the longest had very different diets.

Females fed a diet with a protein to carbohydrate ratio of 1 to 11 lived the longest.

Male mice needed a diet with a protein to carbohydrate ratio of one to 13 for a long life.

The mice on these higher carbohydrate diets lived 30 per cent longer than other mice.

Professor Le Couteur said the take home message from the study was not to eat more meat if your want to reproduce, because the mice were fed a mix of animal and vegetable protein.

“Animal protein was associated with bad health outcomes, it’s a bad for your health as smoking,” he said.

And the carbohydrates eaten by the mice were not the high sugar, refined carbohydrates that make up the bulk of human diets.

The mice were fed whole grains and complex carbohydrates, he said.

What would happen if you ate a higher protein diet when you were young and were reproducing and shifted to a higher carbohydrate diet as you aged, could you get the best of both worlds?

“That is the $100 question and we’re doing research on that now,” says Professor Le Couteur.