You know those times when you’re, like, really thirsty and water suddenly tastes like the nectar of the gods? If you want to rehydrate after a particularly sweaty workout—and fast—your first instinct might be to turn on the tap and guzzle glass after glass of H2O. But a new study published in the The American Journal of Clinical Nutrition suggests that milk (gasp) might be the better option.
Researchers at St. Andrews University in Scotland investigated the rehydration effects of 13 different beverages on 72 male test subjects by measuring their urine output and fluid balance. When you’re just putzing around and living your daily life, the research indicted that sparkling or still water will suit your hydration needs just fine. In the aftermath of a particularly tough HIIT session or training run, however, skim milk reigns supreme. And there’s a really fun, science-y reason what that’s the case.
Study author Ronald Maughan, PhD, a professor at St. Andrews’ School of Medicine, tells CNN that milk’s post-workout merits are due to the fact it contains sugar lactose, protein, and fat, which slow down the natural process of your body emptying fluid from the stomach. These three components perfectly combine to help you stay hydrated over a longer period of time. The sodium in milk also helps your body hold the water and keeps it from producing as much urine.
Ranking right after skim milk was oral rehydration tablets, full-fat milk, orange juice, cola, diet cola. I’m sorry to report that you won’t find alt-milk on this list, because, as Keri Glassman, RD, CDN, previously told Well+Good, vegan milks have very different sugar, protein, and fat content. “Alternative milk beverages wouldn’t work the same way because they have pretty different nutrition profile, a lot less and a different type of protein and carbs, as well as fewer calories,” she says. So if you’re a plant-based kind of person, stick with a tall glass of water and rehydration tablets, like Liquid IV or nuun, for your post-workout refuel.
Here’s what a registered dietitian thinks of oat milk as an alternative: