Betaine: A comprehensive review on dietary sources, health benefits, mechanisms of action, and application

Background: Betaine (N, N, N-trimethylglycine) is a naturally occurring compound, and found widely in many animal and plant foods, such as grains, seafood, vegetables and fruits. As a novel functional food ingredient, betaine has received more and more attention. Scope and approach: This review summarizes and discusses dietary sources, health benefits, safety and application of betaine, with a special focus on its underlying mechanisms of action. Furthermore, future research directions for betaine are suggested. Key findings and conclusions: Betaine has variety health benefits, such as antioxidant, anti-inflammatory, antiobesity, anti-diabetic, hepatoprotective, neuroprotective and cardiovascular protective activities, regulating gut microbiota, as well as kidney protection. Betaine has a wide range of applications in many fields, such as functional foods, pharmaceutics, cosmetics, and personal care products. This paper aims to provide a foundation for the future development of betaine as functional foods.