Findings in a 2016 study published in The American Journal of Clinical Nutrition suggest that water isn’t the best drink for hydration — at least in terms of long-term bodily fluid balance. The answer is actually milk, which may be shocking. Both skim and whole milk can be more hydrating than still water, even when accounting for the drink’s inherent water content.
Hydration isn’t only defined by fluid balance, but also retention, meaning the beverage’s benefits aren’t quickly lost due to urination. Nutrients in milk like fat, lactose (or milk sugar), and sodium (or salt) contribute to its ability to stay in the body longer, thus providing more hydration. Sodium, in particular, is an electrolyte — the body’s most common one, according to the Cleveland Clinic. Electrolytes are notably helpful in terms of maintaining body fluid balance.
The study authors from the St. Andrews University School of Medicine in Scotland carried out testing to develop a beverage hydration index. Nearly 90 people participated in the study, and milk’s hydrating effects weren’t the only surprise noted in the results — orange juice actually proved to be surprisingly hydrating as well.
Proper hydration is critical for many body functions. We feel better and think better when our bodies are properly hydrated, notes the Harvard T.H. Chan School of Public Health. Hydration also plays an important role in maintaining our body temperature and providing nutrients to our cells. Water is traditionally the beverage recommended for hydration.
There are daily minimums touted in terms of the water we should drink to stay hydrated. For men, this total is 3.7 liters; for women, it’s 2.7 liters. Water isn’t the only beverage we drink, though, and other options can also be useful for helping us stay hydrated. As the Mayo Clinic points out, one of the reasons milk and orange juice are so hydrating is that they’re composed mostly of water. Both milk and orange juice, in fact, have a water content of nearly 90%.
Not all beverages are quite as hydrating, however, despite their high water content. Sugary sodas, for example, may seem hydrating, but they cause water loss over time — this is because water is needed to help your body process the sugars. Coffee and teas, by contrast, are more hydrating, particularly when a little milk is added to offset caffeine’s diuretic qualities. Diuretics, which remove water from the body through frequent urination, can actually be dehydrating, as is the case with alcohol.
In order to measure retention and long-term effects of hydration, the authors of the 2016 study published in The American Journal of Clinical Nutrition looked at the level of hydration two or more hours after beverages were consumed. Both milk (skim and whole) and orange juice proved more hydrating than water, with better measurements up to four hours after consumption. After accounting for water content, however, only milk was more hydrating than water.
“This study tells us much of what we already knew,” noted dietician Melissa Majumdar to CNN Health. “Electrolytes — like sodium and potassium — contribute to better hydration, while calories in beverages result in slower gastric emptying and therefore slower release of urination.”
That doesn’t mean, of course, that we should be relying on milk rather than water for the bulk of our hydration. Milk, despite its excellent hydration qualities, also has a lot of calories. However, it can be a great way to recover from high-intensity workouts. Fruit juice, too, is another good beverage for hydration, as suggested by the study results. Juices that contain added sugars, however, should be avoided.
