Methionine restriction

Methionine restriction (MR) is the dietary reduction of the sulphur amino acid methionine without overall caloric restriction. Orentreich and colleagues first reported in 1993 that a methionine-deficient diet extends maximal lifespan in rats; Miller et al. extended this to mice in 2005, showing a longer lifespan and slowed immune and lens ageing on a low-methionine diet. Proposed mechanisms include reduced one-carbon flux, lower hepatic IGF-1 and altered hydrogen-sulphide signalling. Plant-based protein sources (legumes, cereals) tend to be relatively low in methionine compared with animal protein (eggs, meat, dairy), so a partially plant-leaning diet shifts intake downwards. Human data are limited to short-term metabolic studies; MR is a mechanistic concept rather than a validated clinical intervention.