Top Surprising Study Reveals: Water Isn’t the Most Hydrating Drink
Why Your Favorite Beverage Might Be Better at Hydration Than Plain Water
For decades, we’ve been told that drinking eight glasses of water a day is the gold standard for staying hydrated. But a recent scientific study has flipped that idea on its head, revealing that plain water may not be the most effective way to hydrate the body. That honor, surprisingly, goes to certain beverages you might not expect—some of which are already in your fridge.
The Study That Shook Up Hydration Advice
Researchers at St. Andrews University in Scotland conducted a study to measure how different beverages affect hydration levels in the body. Participants were given various drinks, including still water, sparkling water, milk, juice, coffee, tea, and soda. Then, scientists tracked fluid retention and urination rates to determine which drinks kept the body hydrated the longest.
Their surprising finding? Milk—both full-fat and skim—proved more hydrating than plain water. So did oral rehydration solutions (used to treat dehydration), and even orange juice.
Why Water Isn’t the Most Hydrating
Water is still great for hydration—it’s calorie-free, widely available, and essential for countless bodily functions. However, water lacks electrolytes, sugars, and other nutrients that help the body retain fluid. When you drink plain water, especially in large amounts, much of it passes through the body quickly, causing you to urinate sooner. This means your body doesn’t necessarily hold onto it for long-term hydration.
In contrast, drinks that contain a small amount of salt, sugar, and fat—like milk or juice—stay in the system longer because they slow down the emptying of the stomach and provide nutrients that help the body absorb and retain fluids more effectively.
The Beverage Hydration Index (BHI)
To quantify hydration potential, researchers developed the Beverage Hydration Index (BHI). Water was used as the baseline (with a BHI score of 1.0). Beverages with a score higher than 1.0 were more hydrating than water. Some results:
Skim milk: 1.5
Full-fat milk: 1.4
Orange juice: 1.1
Oral rehydration solution: 1.5
Sports drinks: Slightly more hydrating than water
Coffee and tea: About equal to water in hydration, despite their caffeine content
Interestingly, caffeinated beverages like coffee and tea were not dehydrating, as commonly believed. In moderate amounts, their hydration effect was virtually identical to that of water.
What This Means for Your Daily Routine
Before you swap your water bottle for a gallon of milk, it’s important to understand context matters. While milk and other beverages may provide better fluid retention, they also come with calories, sugars, or fats that may not suit every diet or health goal.
Here are a few hydration tips based on the findings:
Mix it up: Don’t rely solely on plain water. Add in hydrating foods and nutrient-rich drinks like low-fat milk or orange juice.
Hydrate with meals: Consuming fluids along with food can help slow fluid absorption and improve retention.
Be mindful of sugar: Some hydrating beverages (like juice and sports drinks) contain high levels of sugar. Use moderation.
Include electrolytes: Especially after exercise or during hot weather, drinks with sodium, potassium, and magnesium can help you retain fluid.
Don’t fear coffee or tea: In moderate amounts, they’re just as effective as water for hydration.
Hydration Isn't One-Size-Fits-All
Every body is different, and hydration needs vary depending on age, activity level, climate, and overall health. Water is still a crucial part of a healthy lifestyle, but this study invites us to take a more nuanced look at how we hydrate.
For athletes, elderly individuals, or those in hot climates, drinks with electrolytes or nutrients may offer better support for staying hydrated over the long term. Meanwhile, those watching their calorie intake or sugar levels might still prefer water as the go-to beverage—just with the understanding that it may need to be consumed more frequently.
Final Thoughts: Time to Rethink Your Drink?
The idea that water isn’t the most hydrating beverage may feel shocking, even heretical. But science is all about challenging assumptions. This study doesn’t knock water off its pedestal—it simply expands our understanding of hydration and encourages us to think critically about our fluid intake.
So the next time you reach for something to quench your thirst, remember: hydration is more than just drinking water—it’s about choosing fluids that your body can hold onto. And sometimes, a glass of milk or juice may do the job even better.
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