A newly published review of more than 350 studies suggests that eating less protein could slow biological ageing, improve metabolic health and, in some circumstances, extend lifespan.
The conclusion challenges the “more protein is better” message that has shaped product development across the nutraceutical sector.
The review — titled The Hallmarks of Protein and Amino Acid Restriction in Aging and Longevity — was published in Cell Press Blue in July.
What did the review find?
The authors examined the effects of protein restriction on metabolic health, nutrient sensing, cellular senescence, mitochondrial function and the epigenome.
Fibroblast growth factor 21 (FGF21), a hormone that rises when dietary protein is limited, was highlighted as a possible mechanism.
Higher FGF21 levels are linked to increased energy expenditure, better blood sugar regulation and reduced inflammation.
Mice with elevated FGF21 have been shown to live longer than controls; plus, eating less protein has also been shown to raise FGF21 in humans.
The review also identified three amino acids, methionine, isoleucine and valine, that appear to drive many of these effects.
Several recent clinical trials found that people who reduced protein intake lost weight, reduced body fat and improved fasting blood sugar — even when they consumed more calories overall.
The authors stress that this does not establish that protein restriction extends human lifespan.
“It’s absolutely crystal clear that there are benefits of protein to muscle growth and exercise response of active individuals,” said Lamming.
Because most people are relatively sedentary, many people are likely consuming more protein than they actually need, which probably has negative health consequences.
Risks for certain groups
Critics have noted that the review relies mainly on rodent and insect research and that whether protein restriction benefits healthy ageing in humans remains unanswered.
Some nutrition experts have also warned that the evidence doesn’t justify broad advice to cut protein, particularly for older adults.
The authors emphasised that requirements vary, with pregnant women, some older adults and regular exercisers all needing more protein.
The US recently revised its dietary guidance to 1.2-1.6 g/kg of body weight — nearly double the previous recommendation.
What does it mean for the nutraceutical industry?
For protein manufacturers, the findings arrive as protein-fortified products spread into cereal, coffee and even bottled water.
Blanket “high protein” positioning could face more scrutiny, while products targeted by life stage and activity level may be better placed.
For longevity brands, the focus on specific amino acids and FGF21 points towards more targeted formulation around metabolic health and healthy ageing.
The limited human evidence, however, means any claims will need careful substantiation.
Lamming said the research points to a more personalised approach: “We probably need to personalise protein recommendations based not just on age, but also on how physically active people are.”
