Recent animal research published in Cell Metabolism reveals that incorporating specific amounts of single amino acids into a low-protein, plant-based diet significantly decreases frailty and fat in mice. A comprehensive analysis of epidemiological data involving over 200,000 participants indicates similar health benefits.
A predominantly plant-based, low-amino acid diet optimizes healthspan, necessitating moderate methionine intake to minimize frailty. Image credit: Fanti et al., doi: 10.1016/j.cmet.2026.05.015.
“The combined findings from both mouse and human studies indicate that a ‘longevity diet,’ primarily vegan or vegetarian with moderate fish intake, may offer the best health outcomes,” stated Valter Longo and his research team from the University of Southern California.
“The Mediterranean diet supplies adequate, albeit small, levels of methionine and other essential amino acids.” Research shows that Mediterranean nations enjoy some of the highest life expectancies, despite exhibiting notable frailty levels.
Given that plant-based foods contain lower essential amino acid levels compared to animal foods, Dr. Longo’s team developed a longevity diet enriched with small amounts of methionine to test its effects on frailty risk.
In this study, groups of 20-month-old mice were provided with one of four distinct diets: a high-fat, high-sugar Western diet, a low-carbohydrate ketogenic diet, or a low-protein longevity diet supplemented with methionine (LDMM).
Mice on the LDMM diet exhibited significantly improved outcomes, such as extended healthy lifespans (the percentage of life spent in good health), reduced fat mass, and decreased frailty.
“While we anticipated varying results from different diets, the dramatic metabolic shifts achieved by merely adjusting the methionine levels in the longevity diet were astonishing,” explained Maura Fanti, a researcher at USC.
“This suggests that not just the total protein contribution, but also the specific amino acid composition, could serve as a targeted approach for metabolic intervention.”
“Moreover, the study identified several biomarkers that indicate improved cardiometabolic health in LDMM mice, including elevated levels of signaling molecules that regulate metabolism and aging, such as GLP-1.”
“Although mice and humans have differing regulatory pathways, witnessing such synchronized changes in multiple metabolic hormones is promising, and we eagerly anticipate similar effects in human studies.”
Notably, mice administered the LDMM diet consumed more food than those in any other group and managed to maintain similar caloric intake while losing fat without sacrificing lean body mass—provided that methionine levels were kept low enough.
Additionally, human data highlighted that participants consuming the highest amounts of animal protein—marked by elevated methionine and essential amino acid intakes—exhibited greater obesity prevalence and double the diabetes incidence compared to those with minimal or no animal protein intake.
“This trend persisted despite higher animal protein consumers having lower caloric intakes and generally healthier diets,” Dr. Longo noted.
“This challenges the traditional belief that calorie reduction is essential for weight loss while emphasizing the need for clearer insights into the underlying mechanisms.”
“Insufficient methionine levels can lead to weakness, while excess methionine may counteract the diet’s benefits, which is inspired by the dietary patterns of traditional long-lived populations like those in Italy and Okinawa.”
“The results indicate that overall protein consumption may be less critical than the intake of specific amino acids.”
“The next phase for the research team involves conducting a controlled clinical trial of the LDMM approach in humans.”
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Maura Fanti et al. A longevity diet supplemented with methionine increases growth hormone, GLP-1, and FGF21. It reduces frailty and promotes a healthy lifespan. Cell Metabolism published online June 23, 2026. doi: 10.1016/j.cmet.2026.05.015
Source: www.sci.news
