Off The Record

The Drink That Will Keep You Hydrated Most On A Hot Sunny Day – And It’s Not Water

Published on August 1, 2023

Some parts of Ireland have seen temperatures as high as 30 degrees Celsius due to the recent heatwave.

Dehydration is a common problem in warmer climates, and staying hydrated is crucial, but is water really the best choice?

When it comes to satisfying your body’s thirst, water is an excellent option. There are no calories and no cost associated with drinking tap water.

How much should I drink?

Niamh Hennessy, Lead Dietitian at Bupa Cromwell Hospital, estimates that the average adult should consume between 2 and 2.5 liters of liquids every day.

Water has many functions in the human body, including waste elimination via urine, joint lubrication, nutrient transportation, and temperature regulation.

“The needs of a physically active person with an outdoor job on a hot day may be different from the person who lives in an air-conditioned house, who drives an air-conditioned car to an air-conditioned office,” said Professor Ron Maughan of the School of Medicine at St. Andrews University.

It’s important to replenish the fluids you lose every day by drinking water and eating foods high in water content.

And as Professor Maughan points out, “replacing lost fluid just with plain water means the body has too much water and not enough salt, so to even things out, it will get rid of water by producing urine.”

It may seem like a monumental task to drink the necessary eight(ish) glasses of water every day.

He also says that milk is a good way to replenish fluids on a warm summer day.

“For this reason, milk can actually be more effective than drinking water. Milk naturally contains salt and lactose, a sugar, which we need in small amounts to help stimulate water absorption in the gut,” Maughan says.

St. Andrews University in Scotland conducted a study to determine which beverages were most effective in keeping participants hydrated.

The study discovered that while water is effective in rehydrating the body rapidly, beverages with a small amount of sugar, fat, or protein are even more effective at doing so for an extended period of time.

Milk, for instance, was discovered to be even more hydrating than plain water due to the presence of the sugar lactose, as well as some protein and fat, all of which contribute to maintaining hydration levels for longer.

Scientists have shown that the electrolytes, carbs, and protein found in milk contribute to its beneficial effects.

Caffeinated beverages have a reputation for being dehydrating, however this is only the case if we consume excessive quantities of caffeine without also consuming sufficient water.

Among a group of 72 healthy, physically active males, the American Journal of Clinical Nutrition compared the hydrating effects of 13 different beverages and found that both fat-free and full-fat milk ranked well, with fat-free milk coming out on top.

When compared to other liquids like water and a sports drink, both types of milk improved the men’s hydration status and kept them hydrated for longer.

Lisa Young, Ph.D., RDN, author of Finally Full, Finally Slim begs to disagree. She says that “Water is the best way to keep yourself hydrated during a sweaty hot day and it’s best for the body and it’s what the body craves.”

If you’re bored of plain water, try one of these:

Electrolyte-enhanced water

“During those hot summer days or a tough workout session, a beverage with electrolytes will help to keep you hydrated or help to replenish you more effectively than just plain water, but assess whether or not you really need the sports drinks with sugar,” says Laura Burak MS, RD, founder of GetNaked® Nutrition and author of Slimdown with Smoothies. “Because these innocent-looking beverages can pack on more calories than you just burned.”

Burak recommends Smartwater, a bottled water brand that restores electrolytes and minerals (such as magnesium, potassium, and calcium) that are lost during the distillation process.

“Smartwater is a top choice because it’s like a sports drink without the liquid calories or sugar,” says Burak. “It is just water with electrolytes which is really all a ‘regular’ person needs.”

She goes on to say that if you’re a serious athlete or spend a lot of time sweating or working in hot locations, the calories and glucose in the other beverages might be useful for keeping your energy up and your electrolyte balance in check.

Blended fruit drink

Fruits high in potassium, such oranges and bananas, are recommended by Young to combat dehydration.

“A fruit smoothie made with banana, berries, unsweetened almond milk, and ice is also super hydrating and rich in potassium,” she says.

Potassium, according to Harvard Health, helps maintain a healthy intracellular fluid balance. It is a mineral that is used as an electrolyte and is required by all human tissues.

This is due to the fact that it carries a weak electrical charge, which stimulates several cellular and neural processes.

Coconut water

According to Sydney Greene MS, RDN, “coconut water is an excellent all-natural way to rehydrate.”

Coconut water, as Greene claims, is a good source of calcium and magnesium in addition to its high potassium content. “This drink has got electrolytes covered,” she explains.

“Coconut water is a great choice on a hot day,” Young says. “Unsweetened coconut water is the best choice, and it also contains electrolytes, including potassium.”

In addition, Greene claims that there is a trace amount of coconut sugar in each meal.