Decoding Betaine: A Critical Analysis of Therapeutic Potential Compared with Marketing Hype—A Narrative Review

Research interest in betaine supplementation has surged in recent years, for both enhancing sports performance and treating metabolic conditions. This surge aligns with an expanding market for betaine supplements, which are often marketed as promising aids for a range of metabolic conditions. Despite numerous in vitro and in vivo studies elucidating betaine’s involvement in crucial metabolic pathways, consensus remains elusive on its clinical efficacy as a dietary supplement, based on results from randomized controlled trials. One analysis of dietary betaine intake in 28 observational studies showed a mean intake of 182 mg/d of betaine, with the main sources including grain-based foods, baked products, grains, cereals, and vegetables. Analysis of the results from human randomized clinical trials has shown that betaine supplementation improves body composition when combined with physical activity. Additionally, betaine supplementation decreases serum homocysteine levels, but does not affect liver enzymes, triglycerides, or high-density lipoprotein cholesterol levels, although it does increase total cholesterol and low-density lipoprotein cholesterol levels at doses ≥4 g/d. Market analysis has demonstrated that betaine is a popular supplement for supporting various physiological processes, such as digestibility, methylation, physical performance, and liver or cardiovascular health. Manufacturers suggest a diverse range of applications for betaine supplements, with 14 different uses identified. Additionally, high variability can be seen in the recommended usage directions for betaine. This narrative research sheds light on the evolving landscape of betaine supplementation and highlights the need for further investigation to clarify its clinical efficacy.