As summer activity climbs — walking, gardening, running, cycling, swimming — so does the body’s demand for fluids. Milk, which is 87–91% water and naturally carries electrolytes and high-quality protein, is increasingly seen as an effective hydration drink for hot weather and exercise, writes Mary Wilcox for Dairy Foods.
Water makes up 45–75% of body weight depending on age, health, diet, activity and environment, factors that shape daily fluid needs as set out in the 2015 National Academies of Sciences, Engineering, and Medicine report on reference intakes for water and key electrolytes. A fluid loss of just 2% of body mass already counts as dehydration and can dull both mental and physical performance, because water underpins thermoregulation, respiration during exercise, digestion, joint and spinal cushioning, tear and saliva production, waste removal and brain function.
Hydration is managed by the brain, which tracks blood-plasma osmolality driven by sodium, chloride, potassium, magnesium and sulfate, and signals the kidneys to conserve or excrete water accordingly. Extreme imbalances can be life-threatening, while balanced hydration is linked to lower risk of cardiovascular, metabolic and renal disease. The National Academies recommend roughly 15.5 cups of total water a day for men and 11.5 for women (about 3.7 and 2.7 liters), from water, other drinks and water-rich foods.
Hydration also matters for weight management. A 2025 review in the Jordan Journal of Agricultural Sciences reported that higher water intake can affect metabolism, appetite, hormonal balance, satiety and total energy intake. With the World Health Organization estimating 2.5 billion overweight or obese adults worldwide in 2022, hydration-supportive drinks are a real opportunity — especially milk and dairy-based beverages that deliver water and nutrients together. The rise of GLP-1 medications, which curb appetite and thirst and raise dehydration risk, only sharpens that case.
Milk’s composition supports the claim: its 87–91% water content comes with sodium, potassium, calcium and magnesium that aid fluid balance and water retention, while its carbohydrates and complete protein help muscle recovery — a combination particularly useful for GLP-1 users. The evidence base is growing too: a 2015 Beverage Hydration Index (BHI) trial in the American Journal of Clinical Nutrition found whole and skim milk scored higher than water and performed much like oral rehydration solutions.
Matt Pikosky, Ph.D., R.D., vice president of nutrition research at the National Dairy Council, notes that milk is not right for every moment. For those who find a creamier, heavier drink unappealing around exercise, he points to milk permeate — a dairy ingredient made by ultrafiltering milk, which strips out protein and fat but keeps the naturally occurring minerals and carbohydrates. It can be formulated into a clear beverage comparable to a conventional sports drink, with demonstrated hydration benefits.
A 2020 Nutrients study on a milk permeate-based oral hydration solution showed it improved fluid retention, cut cumulative urine output and held a positive fluid balance longer than water or a standard carbohydrate-electrolyte sports drink, which researchers credited to its higher mineral content and osmolality. A 2026 study validated and extended those results, finding the same permeate-based drink rehydrated participants better than traditional sports drinks and water, keeping fluid on board for several hours after exercise.
As Pikosky puts it, dairy keeps proving it can meet a range of consumer hydration needs: milk for water, electrolytes and high-quality protein, and clear milk permeate-based drinks as a lighter option with dairy’s natural electrolytes. That built-in balance of electrolytes, protein and carbohydrate is hard for plant-based rivals to match — and by innovating on portion size, packaging, flavor and functional add-ins, the dairy sector can keep expanding across hydration, wellness and performance.
About the author
Mary Wilcox is the founder of Significant Outcomes LLC, an Ohio-based consultancy providing technical and business expertise across the dairy and food industries. She holds a B.S. in Biological Science, an M.S. in Animal Nutrition and an MBA. Learn more at site.
Source: Dairy Foods
