Drinking cold water is perfectly safe for most people and offers a real advantage during exercise, where it helps keep your body cool. Outside of physical activity, cold water hydrates you just as well as room-temperature water. There are a few situations where it can cause minor discomfort or worsen existing conditions, but for the average healthy person, the temperature of your water comes down to preference.
The Calorie-Burning Claim Is Real but Tiny
One of the most popular reasons people reach for ice water is the idea that it forces your body to burn extra calories warming it up. This is technically true. Your body does spend energy raising cold water to its core temperature of 98.6°F. The problem is the amount: a glass of ice water burns roughly eight calories more than the same glass at room temperature. That’s less than a single potato chip. Over the course of a day, even if you drank several glasses, the extra burn is negligible. Cold water won’t meaningfully contribute to weight loss.
Cold Water Shines During Exercise
Where cold water genuinely earns its keep is during prolonged physical activity in the heat. A 2025 study in Frontiers in Sports and Active Living tested athletes performing a two-hour task in a 104°F chamber. One group drank water at about 41°F, while the other drank room-temperature water. All eight participants who got cold water finished the full session. Only two of eight in the room-temperature group made it to the end, with the rest stopping early because they felt dizzy, unable to concentrate, or simply couldn’t continue.
The cold water group also had a measurably lower rise in core temperature: about 1.17°F compared to 1.69°F in the room-temperature group by the time the session ended. Beyond the physical cooling, participants reported that cold water felt more refreshing, which helped them stay motivated to keep going. If you exercise in hot conditions, cold water is a clear and practical advantage.
How Cold Water Affects Your Heart Rate
Drinking cold water triggers a brief, predictable shift in your cardiovascular system. The cold stimulates nerve fibers in your mouth, esophagus, and stomach that activate the vagus nerve, a major pathway connecting your brain to your heart and gut. The result is a temporary dip in heart rate. In a study of young, healthy women, resting heart rate dropped from about 73 beats per minute to around 68 within moments of drinking cold water, then gradually returned to normal over the next 10 to 20 minutes.
This is not dangerous for healthy people. It’s actually your body’s built-in safety mechanism: cold water briefly raises blood pressure through blood vessel constriction, and the vagus nerve responds by slowing the heart to prevent any spike from getting too high. For most people, this happens seamlessly and without any noticeable sensation.
Cold Water and Nasal Congestion
If you have a cold or sinus congestion, you may want to skip the ice water. A study testing 15 healthy subjects found that drinking cold water significantly slowed nasal mucus movement, dropping it from 7.3 millimeters per minute to 4.5 millimeters per minute. That mucus velocity hadn’t recovered even 30 minutes later. Slower mucus clearance means your nose stays stuffier for longer.
Hot water and hot soup, by contrast, temporarily sped up mucus flow. This is why warm liquids feel soothing when you’re sick. It’s not just psychological comfort; warm fluids actively help your sinuses drain. When you’re congested, warm or hot beverages are the better choice.
Migraines and Cold-Stimulus Headaches
Some people get a sharp headache after drinking very cold water, and it’s more than just brain freeze from ice cream. In a study of 669 women, 7.6% developed a headache after drinking just 150 milliliters (about five ounces) of ice-cold water through a straw. Women who had experienced a migraine in the past year were twice as likely to get one of these cold-triggered headaches compared to women who had never had migraines.
The mechanism involves a cold-sensitive receptor in your mouth and throat that, when activated, can stimulate the trigeminal nerve, the main pain-sensing nerve in your face and head. In people prone to migraines, this nerve is already more reactive, which is why cold water can tip it into producing pain. If you notice that cold drinks consistently give you headaches, drinking water closer to room temperature is an easy fix.
Digestive Conditions Where Cold Water Can Be a Problem
For people with achalasia, a condition where the esophagus has trouble moving food down into the stomach, cold water can make symptoms noticeably worse. A study in the Journal of Neurogastroenterology and Motility found that cold water increased resting pressure in the lower esophageal sphincter (the muscular valve at the bottom of the esophagus) and prolonged the duration of esophageal contractions. In practical terms, cold liquids can cause that valve to spasm and slow the passage of food, worsening swallowing difficulty and regurgitation. Nine out of 12 patients in the study reported discomfort from cold food and drinks.
People with acid reflux or other esophageal motility problems sometimes report similar discomfort with very cold beverages, though the effect is most pronounced in achalasia. If swallowing feels harder after cold drinks, warmer liquids are worth trying.
The Bottom Line on Temperature
For most healthy people in everyday life, cold water is fine. It hydrates identically to warm water, and the cardiovascular and metabolic effects are minor and temporary. During exercise or in hot weather, cold water is actively beneficial. The situations where cold water works against you are specific: nasal congestion, migraine susceptibility, and certain esophageal conditions. Outside of those, drink your water at whatever temperature you enjoy. Staying hydrated matters far more than the number on the thermometer.