The Truth About Caffeine, Dehydration, and Extreme Heat

Yahoo

18-07-2025

Key Points
Much of the U.S. faces heat advisories with heat index up to 109°F, prompting the National Weather Service to recommend hydration, limiting outdoor activities, and wellness checks.
The CDC advises avoiding caffeine, alcohol, sugary drinks, and very cold beverages during extreme heat, as they can lead to fluid loss or cause discomfort like stomach cramps.
Some health experts suggest matcha as a milder coffee alternative during heatwaves, citing its lower caffeine, steady energy, and less dehydration from L-theanine.Now is the perfect time to hide away under a rock, as it might be the coolest spot in town — at least temperature-wise. At the very least, you can still relax there with a cup of coffee in peace.
On Wednesday, large portions of the United States were once again under a heat advisory, including "portions of northern Delaware, central, northern, and southern New Jersey, and southeast Pennsylvania," reaching heat index values of up to 102 degrees, according to the National Weather Service. On Thursday, areas of "southeast Maryland, northeast North Carolina, and central, east central, eastern, north central, south central, and southeast Virginia" also faced a similar warning, with "Heat index values of 105 to 109 degrees expected." In both advisories, the National Weather Service warned people to "drink plenty of fluids, stay in an air-conditioned room, stay out of the sun, and check up on relatives and neighbors." It added, "Take extra precautions when outside. Wear lightweight and loose-fitting clothing. Try to limit strenuous activities to early morning or evening. Take action when you see symptoms of heat exhaustion and heat stroke."
Related: What's the Difference Between Cold Brew and Iced Coffee?
However, there's one more warning people should heed with this heat, and that's from the Centers for Disease Control and Prevention.
"Don't drink liquids that contain caffeine, alcohol, or large amounts of sugar — these actually cause you to lose more body fluid. Also, avoid very cold drinks because they can cause stomach cramps," the CDC wrote in its Extreme Heat guidance. It doubles down on this warning on its Heat and Your Health page, though with softer language, stating, "Consider limiting beverages high in sugars and sodium, caffeine, and alcohol, if possible."
Considering most of the eastern seaboard is under either "major" or "moderate" heat warnings, that advice can be overwhelming. But is it really necessary to give up your favorite cup of joe when the mercury rises?
"The CDC's advice reflects an abundance of caution approach to dehydration in high-risk settings (such as extreme temperatures), but it isn't a one-size-fits-all situation," Jason Eastty, nutrition expert and owner of Healthspan Longevity, shared. "In moderate amounts (up to 400 milligrams per day), caffeine does not cause net fluid loss in regular consumers. Habitual caffeine drinkers develop a tolerance to its mild diuretic effect, so coffee and tea both contribute to your daily fluid intake."
Want to really negate any diuretic effects? Take a walk after that cup of coffee. A 2015 literature review study published in the Journal of Science and Medicine in Sport found that "Caffeine exerted a minor diuretic effect which was negated by exercise." The findings added, "Concerns regarding unwanted fluid loss associated with caffeine consumption are unwarranted, particularly when ingestion precedes exercise."
Related: The Top 10 US Cities for Coffee, According to the Experts
Still, the positive benefits of simple drinks during a heatwave shouldn't be overlooked. "The main thing is to keep hydration simple," Dr. Hussain Ahmad, a consulting practitioner at Click2Pharmacy, explained. "Water is the best option. Oral rehydration solutions or electrolyte drinks can help if you've lost a lot of fluid through sweat, vomiting, or diarrhea. Avoid fizzy drinks, alcohol, and overly sugary juices as they're not helpful and can actually make dehydration worse."
This advice, Ahmad noted, is especially important for young children, older adults, people with chronic health conditions, and those working outdoors in high temperatures. "They're more likely to get dehydrated quickly, and small choices (like what you drink) can make a big difference," he added.
If you really can't do without your caffeine, licensed nutritionist and health expert Linda Lin shared that there are some good alternatives. "If you're going to have caffeine, matcha is a gentler choice than coffee," Lin said. "It has less caffeine overall, and it delivers it more gradually, thanks to an amino acid called L-theanine. That means less of the jittery spike and more of a calm, focused energy. It's also less dehydrating and easier on your nervous system, especially in the heat."Lin also mentioned not to forget that "you can eat your hydration too. Juicy fruits are amazing — they give you fluids, minerals, and a little natural sugar for energy and to help with absorption. Oranges, watermelon, cucumbers, and berries are some of my go-tos."
Related: Move Over, Cold Brew, Yemeni Coffee Is Having a Moment
As for the recommendation to avoid cold drinks, Ahmad added that "most people can have them without any problem. But in extreme heat or after a lot of physical activity, very cold fluids might cause a bit of stomach cramping in some people. It's more about comfort than safety."
So, if you have to, it's better to be safe than sorry and avoid these drinks. Or, just go back under your nice, cool rock and invite us over for a drink.Smart hydration options
If you're cutting back on caffeine, alcohol, or sugary beverages during a heatwave, you're not limited to plain water. Here are expert-approved (and actually enjoyable) alternatives to help you stay cool and hydrated:
Coconut Water: Naturally rich in potassium and electrolytes, it's a great low-sugar option for rehydration, especially after sweating.
DIY Electrolyte Mix: No sports drink on hand? Mix water with a pinch of sea salt, a squeeze of lemon or lime, and a splash of fruit juice. It replenishes minerals without the artificial stuff.
Herbal Iced Teas: Caffeine-free blends like hibiscus, rooibos, peppermint, or chamomile can be steeped and chilled. Bonus: Hibiscus tea may help lower body temperature and blood pressure.
Water-Rich Fruits: Snack on produce like watermelon, cantaloupe, cucumbers, and oranges. They're over 90% water and deliver fiber, vitamins, and natural sweetness.Read the original article on Food & Wine