Study Finds Plant and Fish-Based Diet Improves Health in Aging Mice

The study was bolstered by an analysis of dietary and health data from over 200,000 individuals, conducted by researchers from USC, the University of Toronto, and Harvard University. The analysis indicated that individuals adhering to more plant-focused eating patterns exhibited lower rates of obesity and Type 2 diabetes.

The results from both the mouse and human data suggest that a Mediterranean-inspired "longevity diet," which prioritizes vegan or vegetarian foods supplemented with fish, could provide significant health benefits. Senior author Valter Longo noted that the diet maintains low but sufficient levels of methionine and other essential amino acids.

Longo has a lengthy history of studying the relationship between nutrition and aging, focusing on the traditional low-protein, plant-centered Mediterranean diets associated with longevity in certain southern European populations. Despite these populations having some of the world’s highest life expectancies, they often experience high levels of frailty in old age. Longo's modified diet design incorporates a small amount of methionine to explore whether it could mitigate frailty while preserving the benefits of a plant-based approach.

In the study, researchers fed 20-month-old mice one of four diets: a standard diet; a Western diet high in fats and sugars; a low-carbohydrate ketogenic diet; or a low-protein, methionine-supplemented longevity diet (LDMM). Mice on the LDMM outperformed all other groups, enjoying a longer healthspan, reduced body fat, and fewer signs of frailty.

USC Leonard Davis Research Associate Maura Fanti, the first author of the study, remarked on the significant metabolic changes observed from adjusting a single amino acid, underscoring the importance of amino acid composition due to its potential impact on metabolic interventions.

Notably, despite higher food intake, mice on the LDMM lost body fat while maintaining muscle mass. This outcome was only observed when methionine levels were kept low yet adequate.

The human analysis corroborated these findings, revealing that participants with higher animal protein consumption had increased obesity rates and were twice as likely to develop Type 2 diabetes compared to those consuming minimal animal protein. Longo emphasized that these discrepancies persisted even though high animal protein consumers reported lower overall caloric intake.

He stated, "This challenges the dogma that calorie reduction is necessary to lose weight, but it also tells us that we need to have clear understanding of the mechanisms. Too little methionine caused frailty, but too much abolished the benefits of this diet, which aligns with the diets of long-lived populations."

The research team plans to conduct a controlled clinical trial to determine if the observed health benefits from the LDMM can be replicated in humans.

The study was conducted by scientists from the USC Leonard Davis School of Gerontology, along with contributors from the University of Toronto, Harvard University, the University of Campinas, the Keck School of Medicine of USC, and Children's Hospital Los Angeles. Funding came from various grants, including the National Institute on Aging and the National Institutes of Health.

Longo has a financial interest in L-Nutra, a company developing medical foods, and has filed patents related to the Fasting-Mimicking Diet. Longo and Fanti are also listed as inventors on a U.S. provisional patent application pertaining to the study’s methods and findings.