Although soaking in hot tubs filled with red wine may not sound that appealing in the middle of summer, some people—like the New York Knicks’ Amar’e Stoudemire—swear by the expensive spa treatment’s health benefits. That’s because red wine has antioxidants that, at least popularly, are thought to hunt down free radicals that can damage proteins and DNA in the body. (Scientists are actually still evaluating how these compounds function in humans.) Now, a new video from the American Chemical Society dives into the science behind the health claims. The video explains that although red wine does have antioxidants, most of them are phenolic compounds—responsible for flavors and color in red wines—that don’t penetrate skin well. And the longer the wine is out of the bottle, the more the antioxidants are reacting with oxygen in the air and losing whatever “thunder” they had in the first place.