Betaine: Can it improve body composition and performance in women?

Trimethylglycine is a molecule that is structurally the amino acid glycine with three methyl groups attached to it. In chemistry, betaine^[1] refers to a category of molecules, with trimethylglycine, technically, being a betaine. However, as trimethylglycine was the first betaine discovered and named “betaine” because it was found in sugar beet, the terms trimethylglycine and betaine are used interchangeably in the literature.

While betaine can be produced in the body from the oxidation of choline in the liver and kidneys, it can also be obtained from food^[2] such as wheat, spinach, beets, and shellfish. You can find more info on some top betaine-rich foods in Figure 1. The average intake^[3] of betaine from foods in U.S. adults is 100-400 milligrams per day, but its ergogenic and body composition effects have been observed at doses of 2.5 grams per day.

While there is quite a bit of research on betaine’s effects in animals, the literature investigating its ergogenic and body composition effects in humans is limited. Overall, the results from the available research are inconsistent, with some studies suggesting that betaine may improve performance^[4] and body composition^[5], while other studies report no relevant beneficial effects^[6][7].

There are three main mechanisms through which betaine is believed to act on strength, power, and muscle mass development: (i) as a methyl donor^[1] to increase creatine availability and, consequently, accelerate adenosine triphosphate (ATP) recycling^[8] which, in turn, can improve performance by delaying fatigue^[9] during high-intensity activities; (ii) by acting as an osmolyte^[10] to improve cellular hydration and resilience to stressors^[11], thereby enhancing overall work capacity; and (iii) by activating the protein kinase B-mechanistic target of rapamycin (Akt-mTOR^[12]) pathway, thus augmenting muscle protein synthesis and, therefore, increasing muscle mass.

In addition, a number of mechanisms have been proposed through which betaine may act to reduce fat mass, such as: (i) by promoting the translocation of fatty acids into mitochondria, thereby enhancing fatty acid oxidation^[13]; (ii) by lowering the levels of acetyl-CoA^[14] (the substrate for fatty acid synthesis) and by decreasing the activity and mRNA expression in adipose tissue of acetyl-CoA carboxylase, fatty acid synthase, and malic enzyme, thus reducing the capacity for lipogenesis^[15]; and (iii) by increasing hormone sensitive lipase activity^[16], thereby promoting the breakdown of fatty acids.

To date, only a handful of trials investigating the effects of betaine supplementation on training performance have been conducted, with even fewer trials examining betaine’s effects on body composition, and no studies looking at the effects of betaine supplementation in women when accompanied by structured resistance training. The study under review aimed to add to the body of literature by evaluating the effects of betaine supplementation with resistance training on performance and body composition in young, active women.

Betaine, also known as trimethylglycine, is a molecule synthesized in the body from choline and obtained in small amounts in the diet. In vitro and animal studies have suggested that betaine supplementation may improve body composition and muscular performance, but relevant human research is sparse, especially in women performing structured resistance training. The study under review sought to add to the body of literature by examining the effects of betaine supplementation on strength, power, and body composition in young, active women undertaking a resistance training routine.