Methionine is the only essential sulfur-containing amino acid required for the human body and is involved in important metabolic pathways including protein synthesis, transsulfuration, and one-carbon metabolism. However, in recent years, a large number of studies have shown that restricting dietary methionine intake exerts many physiological functions beneficial to body health. This article comprehensively summarizes the benefits of methionine restriction (MR) including promoting gut health, prolonging lifespan, reducing lipid accumulation and body mass, increasing insulin sensitivity, ameliorating diabetes, atherosclerosis and other cardiovascular diseases, improving learning and memory function, and anti-tumor and anti-cancer effects, as well as the effects of MR on bone and skeletal muscle function and protein synthesis. In addition, the strengths and weaknesses of five MR strategies including protein-restriction diet, vegan diet, diet formulation based on monomeric amino acid, oral methioninase, and injection of recombinant methioninase are reviewed in this article. It also discusses future major research directions, which may provide a theoretical reference for the development and application of new foods containing low levels of methionine and the realization of the health functions of MR.

Sulfur-containing amino acids (SAA), primarily including methionine, cysteine and cystine, are abundant in foods and play important roles in maintaining metabolic health. This article begins with a summary of the effects of varying levels of SAA intake on metabolic health. It discusses the benefits associated with moderate SAA restriction, such as lipid-and glucose-lowering effects, mitigation of oxidative stress, and extension of lifespan. It also covers the detrimental effects of excessive SAA restriction, such as growth retardation, increased oxidative stress, and reduced bone mass. Additionally, it explores the benefits of moderate additional SAA intake, such as promoting protein synthesis, improving liver glucose and lipid metabolism, and regulating redox homeostasis. It highlights the detrimental effects of excessive additional SAA intake, such as glucose and lipid metabolic disorders, increased oxidative stress, and an increased risk of cardiovascular diseases. Subsequently, this article reviews the sample pre-treatments (acid hydrolysis, oxidative hydrolysis, and dithiothreitol oxidative hydrolysis) and analytical methods (indirect analysis after derivatization and spectrophotometry) currently used to detect the SAA content in foods, with a discussion about their advantages and disadvantages. Finally, the methods for achieving SAA precision nutrition and their applications are examined. This review is expected to provide theoretical references for SAA detection in foods and the improvement of metabolic health through precision regulation of dietary SAA intake.