Less dietary protein could grant us a longer life with fewer kids, according to a UNSW researcher.
It's well known that a calorie-restricted diet prolongs lifespan in fruit flies, worms, mice and monkeys, and scientists believe the same applies to humans. However, what wasn't clear until now was whether longevity is improved by calorie-restriction itself or limiting a specific dietary nutrient.
Using flies as study subjects, the report reveals that the secret to long life relies on a fine balance between protein and carbohydrates consumption, rather than caloric restriction. Those fed a diet with a protein to carbohydrate ratio of one to 16 lived twice as long as normal. However, flies that lived on a one to two ratio of proteins to carbohydrates laid the most eggs.
"It has been known for decades that restricting diet can prolong life, but mostly this was thought to be due to reduced calorie intake," says the report's co-author, UNSW's Dr Rob Brooks. "This paper shows clearly that it is restricting protein rather than calories that prolongs life in female flies."
"When given a choice, flies ate an intermediate ratio of protein to carbohydrate that maximised the lifetime number of eggs they produced rather than live as long as possible. That is exactly the way we would predict natural selection to work," he says.
Published in the journal, Proceedings of the National Academy of Sciences, the report is the first of its kind to measure the relationship between diet, nutrient intake, lifespan and reproduction.
Led by University of Sydney researchers, the report is a collaboration including scientists from UNSW together with colleagues from Seoul, Auckland, and Macquarie universities
Sydney University's Stephen Simpson says it would be premature to recommend a low protein diet, and that those who tried it would find themselves "between a rock and a hard place."