Oat milk has gained popularity as a plant-based alternative to traditional dairy milk, with more than a third of Britons choosing it, according to a 2021 report. Its smooth texture and mild flavor make it a favorite in coffee and other drinks. However, the nutritional value and health benefits of oat milk are still being studied and debated by experts. Research has looked into how well different beverages help the body retain fluids. A 2007 study tested various drinks on people who were dehydrated after physical activity. Milk was found to keep more water in the body compared to water or energy drinks. While water kept the body hydrated for up to five hours, the effect of other drinks, including milk, returned to normal after just one hour. A similar study at the University of Limerick, involving seven young men who regularly exercised, found that milk helped restore water balance more effectively, likely due to its nutrient content. In 2016, a study published in The American Journal of Clinical Nutrition compared several beverages, including water, whole milk, skim milk, tea, coffee, sodas, orange juice, beer, energy drinks, and oral rehydration solutions. Both types of milk and the oral rehydration solution were most effective at retaining fluids. A 2020 study in the journal Nutrients confirmed these findings. Milk's ability to retain water is linked to its electrolytes, like sodium and potassium, which help the body hold onto fluids. It also contains calories that slow down the emptying of the stomach, allowing for a more gradual absorption of fluids and delaying the urge to urinate. Dietitian Melissa Majumdar explains that while milk has these properties, it contains only modest amounts of sodium and potassium compared to rehydration solutions. The protein and lactose in milk may play a bigger role in its hydrating effect. Skim milk performs similarly to whole milk, suggesting that fat is not the main factor behind the effect. However, these studies have limitations. They involved small numbers of participants, mostly men, and focused on short timeframes, up to five hours. A Harvard professor has raised questions about whether the difference between milk and water would still be significant over longer periods. These studies also focus on hydration after physical activity, not the broader concept of public health hydration. During heatwaves, the need for continuous hydration over several days becomes more important than optimizing fluid retention from a single drink. In such conditions, drinking about eight glasses of water daily is recommended. Water remains the standard for hydration due to its lack of calories and sugar, and it can be complemented by a diet rich in water, fruits, and vegetables that provide essential minerals. While milk is a nutritious food that provides calories, sugars, and fats, it is not a neutral substitute for water. It may not be suitable for people with lactose intolerance, and it requires careful storage in hot weather. Public health guidelines continue to emphasize water as the primary drink for hydration, with alternatives available for those who prefer other beverages. Drinking excessive amounts of water in a short time can be harmful, potentially lowering blood sodium levels. Consistent, regular drinking is more important than consuming large volumes at once.