A new theory of why dietary restrictions can work to reduce disease risk and increase longevity suggests that it is a sever restriction in nutrient intake, rather than calorie intake, that may result in the well known effect.
The suggestions comes from Australian researchers, who proposed the new evolutionary theory to explain why caloric restrictions and restricted food intakes can result in increased lifespan and a decrease in the risk of diseases associated with old ages – including cancer.
Writing in BioEssays, the team suggest that the real reason behind the well-documented effects of dietary restriction (often referred to as caloric restriction) in laboratory tests may be a scarcity of nutrients in the diet, rather than a reduction in energy intakes.
“This is the most intriguing aspect, from a human health stand point,” commented Dr Margo Adler – who led the study. “Extended lifespan may simply be a side effect of dietary restriction, a better understanding of these cellular recycling mechanisms that drive the effect may hold the promise of longer, healthier lives for humans.”
Nutrients or calories?
The team said a major problem with the current theory - which suggests that a reduction in energy intake in general is responsible for the effects - is that it does not account for the fact that wild animals subjected to dietary restriction are often weaker in terms of their immune response and muscle strength, and therefore actually die younger.
Indeed, Adler explained that since dietary restriction appears to extend lifespan in the lab by reducing old-age diseases, it would be ‘unlikely’ to see the same effects in wild animals or a real-world setting, because those with weaker immune responses are at a higher risk of death at a young age due to infection .
“We think that lifespan extension from dietary restriction is more likely to be a laboratory artefact,” said Adler, who is an evolutionary biologist at the University of New South Wales. “Unlike in the benign conditions of the lab, most animals in the wild are killed young by parasites or predators.”
Cellular recycling: A new theory
Dietary restriction does, however, lead to increased rates of cellular recycling and repair mechanisms in the body, Adler pointed out.
Based on this, the team’s new theory is that this cellular recycling of nutrients has evolved to help animals continue to reproduce when food is scarce; they require less food to survive because stored nutrients in the cells can be recycled and reused.
It is this effect that could account for the increased lifespan of laboratory animals on very low-nutrient diets, because increased cellular recycling reduces deterioration and the risk of cancer, suggested the team.
Published online ahead of print, doi: 10.1002/bies.201300165
" Why do the well-fed appear to die young? A new evolutionary hypothesis for the effect of dietary restriction on lifespan"
Authors: Margo I. Adler, Russell Bonduriansk