Dietitians have warned Australians against jumping on the band wagon of low-protein, high-carbohydrate (LPHC) fads, following the news that LPHC diets may extend a person’s lifespan.
The longevity diet, based on a new study published in the journal Cell Metabolism today, suggests that we might be able to harness the mysterious ‘fountain of youth’ hormone by eating low-protein, high-carbohydrate foods.
Researchers from the University of Sydney’s Charles Perkins Centre claim that the LPHC diet is associated with an elevated production of the ‘fountain of youth’ hormone, called FGF21 (fibroblast growth factor 21) by the liver.
This is important to diet and longevity because FGF21 is thought to play a key role in linking nutrient signaling pathways with those that control aging and health - thus having an overall effect of extending lifespan.
“This research really showed that the diets that were low in protein and high in carbohydrates were the most the effective in increasing FGF21 levels in mice and this was associated with several markers of metabolic health,” lead researcher Dr Samantha Solon-Biet tells SBS.
But does that mean we should all dump our steak dinners and opt for white bread and chips?
Spokesperson for the Dietitians Association of Australia, Associate Professor Duane Mellor, says the study is “a lovely bit of science”. However, he cautions against making any one-size-fits-all recommendations on diet.
This is because people with different body types and those from different cultures may react differently to the same diet, even if they eat identical meals.
“[The research] shows you that different diets can have a similar effect on a biological marker, in this case FGF21, and then have different effects on how that works – its actual use in humans is probably limited,” Mellor says.
"...About a third of the energy of an average Australian comes discretionary food, or what a lot of people would call junk food.”
Mellor also explains there is strong evidence to suggest that people who follow a LPHC diet, as famously observed on the island of Okinawa in Japan and Sardinia in the Mediterranean, have some of the highest life expectancies in the world.
“They do tend to be not terribly high in protein and not terribly high in fat and some of them would have quite a significant amount of carbohydrates.
“They don’t have an excess of discretionary foods, which is probably the main problem in Australia – about a third of the energy of an average Australian comes discretionary food, or what a lot of people would call junk food.”
Mellor explains that instead of making a drastic change to our diets, simply reducing junk food consumption and increasing our fruit and vegetable intake will have similar benefits.
What does this mean for Paleo diets?
The new findings also suggest that Paleo diets featuring high quantities of protein may actually shorten lifespan by activating an anti-ageing pathway in the body called mTOR.
The researchers conducted tests on over 850 mice that were put on one of 25 different diets, which ranged from five to 60 per cent protein content and five to 75 per cent carbohydrates and fat content.
They found that the low-protein, high carbohydrate (LPHC) diet was the best for boosting FGF21 levels in mice, and that the reverse high-protein, low-carbohydrate diet (or paleo diet) had the opposite effect.
“There was a clear sweet spot in which the diet influenced health and longevity, and again this is the low-protein, high-carbohydrate diet,” says Dr Solon-Biet.
“If we can eat a low-protein, high-carbohydrate diet and elevate our levels of FGF21, this could be really one big step forward in helping people live longer, healthier lives by elevating this hormone through diet.”
“There was a clear sweet spot in which the diet influenced health and longevity, and again this is the low-protein, high-carbohydrate diet."
Previous research has shown that this diet also fights obesity by suppressing appetite and regulating the body’s metabolism; boosting the immune system by preventing the age-induced loss of infection-fighting T cells; and, ultimately, extends your lifespan.
More tests are needed to prove that the findings of the study on mice will translate to humans.
However, Dr Solon-Biet, says the next step in the research will be limited to mice as scientists investigate how the signaling works and “exactly what it is amount proteins and carbohydrates that drive these FGF21 levels”.