Tomatoes and pasta

Protein and carbs, not calories, hold the key to long life

28 May 2015
New University of Sydney research shows low protein, high carbohydrate diets could be as effective at extending life as calorically restricted diets.
Heathly food arranged on a heart-shaped plate surrounded by a stethoscope and gym gear

Low protein, high carbohydrate diets could be just as effective as low calorie diets at promoting a long life and good heart and digestive health.

New research from the University of Sydney's Charles Perkins Centre shows the long-reported benefits associated with caloric restriction diets could also be reached with a low protein, high carbohydrate diet.

Published in Cell Reports, the research marks 80 years since the publication of a seminal paper showing that restricting calorie intake in rats by around 40 per cent prolonged their lives. Since that time, caloric restriction without starvation has been found to extend lifespan and improve metabolic health in organisms from yeast cells and worms to mice and monkeys.

"We have known for many years that caloric restriction diets increase lifespan in all manner of organisms," said Professor Stephen Simpson, Academic Director of the Charles Perkins Centre and corresponding author of the paper, published in Cell Reports.

"However, except for the fanatical few, no one can maintain a 40 per cent caloric reduction in the long term, and doing so can risk loss of bone mass, libido and fertility."

The research showed in mice that a low protein, high carbohydrate diet provides the same benefits as caloric restriction - a result researchers believe may also hold true in humans.

"There is one downside. While a low protein, high carb diet is likely to have beneficial effects later in life, it is also associated with an increased food intake driven by protein appetite, which poses the risk of weight gain.

"It still holds true that reducing food intake and body weight improves metabolic health and reduces the risk of diseases like type-2 diabetes, obesity and fatty liver disease.

"However, according to these mouse data and emerging human research, it appears that including modest intakes of high quality protein and plenty of healthy carbohydrates in the diet will be beneficial for health as we age."

We've shown that when compared head-to-head, mice got the same benefits from a low protein, high carbohydrate as a 40 per cent caloric restriction diet.

"If the same applies to us, this would mean healthier ageing, with more pleasure and less pain than caloric restriction."

The results follow research from the Charles Perkins Centre that showed a low protein, high carbohydrate diet promotes longevity and good cardiometabolic health, while a high protein, low carbohydrate diet leads to leaner body mass and better measures of reproductive function, but also shortened lifespan and poor cardiometabolic health.

The game-changing body of work points to the balance and quality of macronutrients (protein, carbohydrates and fat) - rather than caloric intake or the role of any one nutrient - as the major factor in nutritional health.

"We have again shown that changing the macronutrient composition of a diet is vitally important, and in this case is a more feasible intervention than caloric restriction for managing human health," Professor Simpson said.

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