Milk is a better hydrator than water

Milk is a better hydrator than water
Milk is a better hydrator than water

A new hydration index has revealed some surprising results. Contrary to popular belief, beer and coffee are not as bad as they are made out to be. In fact, milk is even more effective at hydrating the body than water.

The question of how much water a person should drink each day to stay healthy and productive is a topic of much debate. There are many different recommendations from experts, but they often conflict.

A new "hydration index for beverages" developed by researchers at the University of Loughborough in the United Kingdom provides the first empirical data on this question. The study found that milk, both whole and skimmed, has a hydration index of 1.5, meaning it retains moisture in the body for 50% longer than water. Orange juice also performed well, with a hydration index of 1.1. All other beverages, such as iced tea, Coca-Cola, hot tea, coffee, beer, or soda, have a hydration index below 1.0, meaning they are excreted from the body more quickly than water. Study lead author Ronald J. Maughan explained in a blog post for,The New York Times«.

A study was conducted on 72 men.

The study participants were 72 men aged 20 to 30 years old. All of them drank one liter of water, plus from 1 to 3 other popular beverages within 30 minutes.

The amount of water that was not excreted after 4 hours was given a value of 1.0. The volume of all other remaining beverages in the body was set in a quantitative ratio. A value greater than 1.0 indicates that more moisture remains in the body, a lower value indicates a higher rate of excretion than water.

Whole milk, skim milk, and orange juice

The result was surprising: 3 beverages had a significantly higher hydration index than water. These were whole milk, skim milk, and special solutions such as Pedialyte. All of them came to values of 1.5. Orange juice also showed 1.1 points – better than water. All other beverages, such as cold tea, Coca-Cola, hot tea, coffee, beer, or carbonated water, were equally worse than water.

Maughan RJ, Watson P, Cordery PA, Walsh NP, Oliver SJ, Dolci A, Rodriguez-Sanchez N, Galloway SD: "A randomized trial to assess the potential of different beverages to affect hydration status: development of the hydration index" – publication in the "American Journal of Clinical Nutrition", March 2016.

Why is milk so hydrating?

Study leader Ronald J. Maughan explained in a blog post on the New York Times: "Normally, the kidneys react normally to water and, in order to get rid of excess water, they produce more urine. However, if the beverage – as in the case of milk – contains mineral particles, such as sodium and potassium, which act as an electrolyte, the stomach empties slowly. The kidneys work in a softer mode, the fluid remains in the body longer."

Coffee and beer do not have a dehydrating effect

Contrary to popular belief, it is possible to consume caffeine, alcohol, and sugary drinks in moderation. The dehydrating effect of coffee and beer is nothing but unproven rumors. Even soft drinks provide the body with moisture just like water, although they contain sugar, and nutrition experts do not recommend their consumption.

The following recommendations can be drawn from the results of the study. It is good to drink milk during a long trip when there is no access to fluids. The same is true for the elderly, who have a reduced sense of thirst, or for the dehydration of small children, especially in the summer. However, it is important to remember that milk is much more calorie-dense than water.