does milk beat water?

Dioralyte (an oral rehydration solution used after fluid loss from diarrhea), tea, coffee, diet cola, regular cola, orange juice, and Powerade. The researchers found that fluid retention was best after drinking either type of milk or the oral rehydration solution; results for the other drinks were similar to water.

Sounds like milk is a winner, right? Maybe. But there are other things to consider.

The study details matter

The findings of these studies aren’t definitive. As with all research, there are important limitations. For example:

• The small number of participants in these studies means that just a few people could have an outsized impact on the results.

• Two of the three studies involved significant dehydration by intensely exercising in a warm environment, leading to several pounds of fluid loss. Therefore, the results may not apply to people engaged in more typical daily activities or workouts.

• The advantage of milk reported in these studies may be too small or too temporary to matter much. For example, in the study of 72 people, milk drinkers produced about 37 ounces of urine over four hours while water drinkers produced 47 ounces. Does the 10-ounce difference have a meaningful health impact? If the study participants had been monitored for a longer period, would this difference disappear?

• The amount of milk consumed in the study of seven men would contain more than 1,000 calories. That may be acceptable for an elite athlete after hours of intensive exercise in the heat, but counterproductive and costly for someone working out for 30 minutes to help maintain or lose weight. Tap water is free and has no calories!

Hyping hydration: Many claims, little evidence

The billboard promoting milk reflects our relatively recent focus on hydration for health. This is promoted — or perhaps created — by advertisers selling sports drinks, energy drinks and, yes, water bottles. But does drinking “plenty of water” translate to weight loss, athletic performance, and glowing appearance? Does monitoring urine color) and downing the oftrecommended eight glasses of water daily make a difference in our health? On the strength of evidence so far, I’m not convinced.

Before water bottles were everywhere and monitoring fluid intake became commonplace, medically important dehydration wasn’t a problem for most healthy people who were not rapidly losing fluids due to heat, intense exercise, diarrhea, or the like.

The fact is, drinking when thirsty is a sound strategy for most of us. And while there are important exceptions, you probably don’t need fluids at hand at all times or to closely monitor daily fluid intake to be healthy.

The bottom line

Despite the claims of milk ads and the iffy studies justifying them, the idea of replacing water with milk for rehydration may not convince everyone: the taste, consistency, and extra calories of milk may be hard to get past.

As for me, until there’s more convincing evidence of an actual health advantage of milk over water for routine hydration, I’ll stick with water. But I’ll forego the water bottle.