Scroll through TikTok, Instagram, or Reddit and you'll quickly find a familiar argument: Which is the better sleep aid—melatonin or magnesium? One camp insists melatonin is the body's natural sleep hormone, the obvious choice for insomnia. The other claims magnesium calms the nervous system, relaxes muscles, producing deeper, more restorative sleep. Millions of views, influencer endorsements, and supplement marketing have turned the question int…