Betaine

What is betaine?

Betaine, also called trimethylglycine (TMG), is a compound found in beets, spinach, wheat bran and other whole grains. The body can also make it from choline. Betaine donates methyl groups in a pathway that converts homocysteine into methionine, which happens largely in the liver, and it helps cells manage water balance. Supplement forms include betaine anhydrous, used in sports and wellness products, and betaine HCl, used as a digestive aid.

What the research says

Animal studies suggest betaine can reduce fat buildup in the liver, which is why it appears in liver-support formulas. Human research on body composition is mixed. A 2019 meta-analysis of six trials with 195 participants found that betaine reduced total body fat mass by about 2.5 kg and body fat percentage by about 2.4 percent, without changing body weight or BMI.

A larger and more recent 2022 systematic review and meta-analysis, however, concluded that betaine supplementation did not significantly affect body weight, BMI, body fat percentage, fat mass or fat-free mass. Results were similar regardless of age, sex, BMI, trial length, dose or health status. With the newer and broader analysis finding no effect, the overall evidence does not support betaine as a weight-loss ingredient.

Claims that betaine can repair or reverse liver damage in people are not supported by strong human trials, and statements like this should be read as marketing rather than established fact.

How it’s used in supplements

In sports nutrition, betaine anhydrous is usually taken in gram-level doses. In multi-ingredient capsules, it typically appears in much smaller, undisclosed amounts, making it unlikely to match the doses used in trials.

The meta-analyses above did not identify safety signals that changed their conclusions, but most trials were short. Because betaine is metabolically active in the liver and kidneys, people with kidney or liver conditions, and anyone pregnant or breastfeeding, should ask their doctor before taking concentrated betaine supplements.

Bottom line: betaine has a plausible role in liver metabolism, but human trials on body composition disagree, and the broadest recent analysis found no benefit. It is not a proven weight-loss or liver-repair ingredient, and the small amounts in multi-ingredient capsules make an effect even less likely. Foods such as beets, spinach and whole grains provide betaine as part of a normal diet. The disagreement between the two meta-analyses is also a useful reminder that a single positive review is not the final word, and that newer, larger analyses can overturn earlier, more optimistic conclusions.