Milk tops water for rehydration, says study

By Helen Glaberson

- Last updated on GMT

Milk tops water for rehydration, says study
Milk can rehydrate active children more effectively than water or energy drinks, according to new research funded by the Dairy Farmers of Canada.

The study, to be published next month in The Proceedings of the XXVIIth International Symposium of the European Group of Paediatric Work Physiology, ​claims that children consuming milk after exercise retained more fluid than those who drunk alternative beverages.

Higher salt content

Milk has a higher salt content than a typical sport drink, study author Brian Timmons from McMaster University, Canada told

The salt in the milk tells the body to retain the fluid, whilst salt lost through sweat is also replaced, he explained.

In addition to loss of water and salt, other minerals such as potassium, calcium and magnesium are lost through exercise, said Timmons.

As the milk also contains protein it may empty from the stomach more slowly,​which would allow the body to gradually retain the fluids, rather than being “flooded​” with plain water, said​Timmons.

However, he said this benefit had not been proven as the scientists had not measured how quickly the drinks emptied from the stomach.


Fourteen children participated in the study, with an average age of nine years.

The participants exercised on a stationary bike (cycle ergometer) for 40 minutes inside an environmental room that controlled temperature at 35 degrees celsius.

During the exercise session, the children dehydrated about 1.5 per cent, which means 1.5 per cent of their body weight was reduced by losing water through sweat.

After the exercise, the participants were given either water, skimmed milk, or a typical sport drink in a volume that equalled how much water they lost during exercise.

The scientists then monitored the children for two hours to see how they rehydrated.

The amount of fluid retained in the body and how much urine was produced as measures of rehydration was analysed.

Each child repeated the exercise on three separate days, about a week apart, so that each child could try the three different drinks.

After two hours of recovery, about 75 per cent of the skimmed milk consumed was retained in the body. In comparison 60 per cent and 50 per cent of the sport drink and water consumed were retained in the body, said the scientists.

Following two hours of recovery, there was twice as much urine produced with water than with skimmed milk.

However, Timmons said it was important to note that all three drinks were effective at rehydrating the children.

“Of course, there’s nothing bad about drinking water after exercise for kids. The water just doesn’t have the same ingredients that help kids replace all of what they’ve lost when they’re active.”

The scientist said the study’s findings were most relevant for children who may be playing multiple games in the same day or attending sports camps, where there is often limited time to recover before the next game or match. has not seen the full data of this study.

The research will be presented next month at the XXVIIth International Symposium of the European Group of Pediatric Work Physiology.

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