We know exercise is good for us , but scientists are still figuring out why, at the most fundamental and molecular level. A new small but long-term study may have yielded a crucial answer, identifying the metabolite betaine as a key driver of the benefits of exercise. Betaine, a small molecule found in foods like sugar beets and spinach, has previously been linked to improved health, but it hasn't been connected to exercise before. In this study, a team led by researchers from the Xuanwu