Why water is the best drink during a heat wave

Katia Hetter, CNN | 7/1/2024, 11:22 a.m.
More water, please. Millions of Americans are experiencing a record-breaking heat wave that has continued for days on end.
Many people don't need to drink anything other than water to hydrate approriately. Mandatory Credit: Frederic J. Brown/AFP/Getty Images via CNN Newsource

More water, please.

Millions of Americans are experiencing a record-breaking heat wave that has continued for days on end.

We know that keeping hydrated is important to staying healthy in the summer heat, but is water still the best drink during a heat wave? Or should people turn to sports drinks instead? What about soda, coffee and beer — is it advisable to keep drinking these beverages during extremely hot weather?

To help guide us through drinks we should choose — and avoid — during hot weather events, I spoke with CNN wellness health expert Dr. Leana Wen. Wen is an emergency physician and clinical associate professor at the George Washington University. She previously served as Baltimore’s health commissioner.

CNN: How much water should people normally drink, and does that change during extreme hot weather?

Dr. Leana Wen: A quick rule of thumb that’s often cited is the “8 x 8 rule,” which is eight 8-ounce glasses of water, or 64 ounces, of water per day for adults. That’s half a gallon. This rule is not set in stone. There are many factors that influence how much water people need, including the type of food they eat, their body size and their physical activity.

Other factors include air temperature and humidity, and, specifically, how much time you spend outdoors during hot weather. People working in the heat or otherwise engaging in physical activity should drink an 8-ounce cup of water every 15 to 20 minutes, according to the US Centers for Disease Control and Prevention. This would total about 24 to 32 ounces per hour. People should also keep well hydrated before and after their outdoor time in the heat.

CNN: Is it possible to drink too much water?

Wen: Yes. The CDC guidance is that people should not drink more than 48 ounces (about 1.5 quarts) of water or other fluids in an hour. A large amount of fluid all at once can dilute the concentration of salts in our blood and be unsafe.

CNN: When it’s really hot outside, is water still the best fluid, or should people turn to sports drinks?

Wen: Sports drinks are beverages with added electrolytes. Their main purpose is to replenish water and electrolytes that are lost with sweating. These drinks contain electrolytes like sodium, potassium, calcium and magnesium. Some have added sugars like fructose, glucose and sucrose.

Most people do not need drinks other than water. In general, adults engaging in mild to moderate physical activity and kids playing on the playground or doing recreational after-school sports do not need electrolyte replacement. The foods that we eat contain the electrolytes we need.

People who could consider sports drinks are athletes who are engaging in vigorous exercise for at least an hour outdoors in hot weather. Again, though, not all these individuals will need electrolyte replacement beyond what they get from eating normally. Whether they do depends on factors such as how much they sweat, how hot and humid the environment is and how intensely they exercise.

CNN: What’s better, a sports drink that comes ready-made in a bottle or an electrolyte powder that you can add to make your own drink?

Wen: Personally, I prefer the powder. There are also tablets that dissolve in water. These do-it-yourself options are cheaper, and I like to choose the brands that don’t have much added sugar or chemicals. But this is a question of personal preference. Whatever you buy, make sure to look carefully at the ingredients. For instance, if you don’t want added sugar or caffeine, make sure what you’re drinking doesn’t have these ingredients.

CNN: What about energy drinks? Are these a good replacement for water?

Wen: This is an important question. The short answer is no, energy drinks are not a replacement for water. They should be used with caution in adults, and children should not drink them.

Energy drinks are different from sports drinks, which are meant to help you restore water and electrolytes. Energy drinks are not meant mainly to hydrate you. They often contain large amounts of caffeine and other legal stimulants such as L-carnitine and guarana. While caffeine can boost energy in the short term, it is also a diuretic, meaning that it causes someone to lose water. Too much caffeine also can cause jitteriness, anxiety and irregular heartbeats.

The American Academy of Pediatrics recommends against energy drinks for children and adolescents. In some studies, though, as many as 30% to 50% of adolescents report using energy drinks. I urge parents to be careful to distinguish between sports drinks and energy drinks. Neither are needed, but energy drinks, in particular, should be used with caution.

CNN: What about other drinks with caffeine, like coffee? Is a cold brew or iced mocha a bad idea in hot weather?

Wen: Not necessarily, though people should be aware that these caffeinated drinks may not hydrate you and may even dehydrate you further. This doesn’t mean you should stop all coffee when it’s hot outside. Just be aware of the effect of caffeine and consider drinking extra water while you are enjoying caffeinated beverages.

CNN: What about sodas, punches and alcoholic beverages?

Wen: Sodas and punches are considered ultraprocessed foods, which have been linked to many adverse long-term health consequences, such as increased risk of diabetes, heart disease and early death. Consumption should generally be kept at a minimum, and hot weather is no exception. Again, water is the preferred substance for hydration.

Alcohol is best avoided when it’s very hot outside. Be especially careful not to drink large amounts and become inebriated, as this could blunt your body’s response to temperature regulation. You also may miss early signs of heat-related illnesses. Alcohol can be dehydrating as well. If you do choose to drink alcohol, limit your drinks, make sure there are people around you in case you get into trouble medically and be sure to drink plenty of additional nonalcoholic fluids.

CNN: What about kids who are in all-day sports camps?

Wen: It’s hard to answer this without knowing exactly how the camp is structured. Many sports camps have indoor activities for at least a portion of the day, and even those that are predominantly outdoors should move their activities indoors during extreme heat warnings.

When in doubt, it’s advisable to speak with the camp director and ask about how much time will be spent outdoors. If the time is limited, there are regular breaks and much of the activity is low to moderate intensity, it’s probably sufficient to hydrate with water and supplement with nutrient-dense snacks such as watermelon, coconut and avocado. Also focus on hydrating before and after camp. Sports drinks probably aren’t needed, and, again, it’s advisable for children to avoid energy drinks.

CNN: What other precautions would you follow during extreme heat?

Wen: Know the symptoms of heat exhaustion and heatstroke. Take extra care of children and the elderly, as well as people with chronic medical conditions that could be exacerbated by the heat. Be careful while exercising and try to move activities indoors or go in the early morning or late evening. And make sure to keep well-hydrated with the best substance for hydration — water!