Water is essential for sustaining life, and drinking enough water is one of the simplest and most effective ways to maintain health. Especially in hot summer weather, proper body fluid maintenance becomes even more critical to prevent heat-related illnesses. Water, which makes up about 70% of our body, is vital for regulating body temperature, lubricating joints, digestion, detoxification, nutrient transport, energy production, and heart and brain function. Recent studies show that adequate hydration can reduce the risk of chronic diseases and premature death, and prevent biological aging.

Dr. Dana Cohen, an integrative medicine specialist in New York, states, "Water intake is essential for every cell function in the body." She warns, "Many people experience low levels of dehydration without realizing it. Chronic dehydration can lead to fatigue, headaches, poor concentration, joint pain, and even cravings that are mistaken for hunger."

Here are the most common myths and truths about hydration, compiled by National Geographic with expert opinions:

Myth 1: Adults should drink 1.9 liters of water daily 

Truth: The common notion that one should drink eight glasses (about 1.9 liters) of water a day is widely spread, but actual fluid needs vary greatly depending on an individual's body size, activity level, and environment. The Institute of Medicine of the National Academies of Sciences, Engineering, and Medicine in the U.S. recommends that women consume about 11.5 cups (about 2.7 liters) and men about 15.5 cups (about 3.7 liters) of fluids daily. This fluid intake includes not only pure water but also all fluids consumed through beverages and food.

Especially when it's hot and humid in summer, or during outdoor activities and exercise, you should drink more water. This is because water is continuously lost through breathing and evaporation from the skin surface, even if you don't visibly sweat. Therefore, it's important to adjust your fluid intake according to environmental changes and activity intensity.

Myth 2: Thirst is a sure sign that you need water 

Truth: While thirst is a useful signal that your body needs water, it already means that a certain degree of dehydration has occurred. Nutrition expert Dr. Wendy Bazilian explains, "Thirst is more like a late-arriving warning light, like the 'E' on a car's fuel gauge." By the time you feel thirsty, your fluid intake is already insufficient.

Particularly for the elderly, the ability to feel thirst dulls with age, increasing the risk of dehydration. Dr. Cohen warns, "Regardless of age, a decrease of just 1-2% in body fluid can impair physical and cognitive performance."

One good way to gauge your body's hydration status is to check the frequency and color of your urine. Dr. Cohen advises, "Ideally, you should urinate every 2-3 hours while awake, and clear or pale yellow urine indicates good hydration."

Myth 3: The only way to stay hydrated is by drinking water 

Truth: According to Dr. Bazilian, about 20% of the fluids we consume come from foods with high water content. Summer fruits and vegetables like watermelon, cucumbers, tomatoes, grapes, and leafy greens are excellent sources of hydration. Foods like smoothies and patbingsu (shaved ice with red beans) also help replenish fluids.

Especially for Koreans who often enjoy soup-based dishes like guk, jjigae, naengmyeon (cold noodles), and kongguksu (noodles in cold soybean soup), the proportion of fluids obtained from food might be even higher. Therefore, consuming fluids through a variety of foods is also an effective method.

Myth 4: Drinking a lot of water at once will keep you well-hydrated 

Truth: If you consume more water at once than your body can excrete, it can lead to hyponatremia. This is a condition where the body has too much water, causing sodium levels to drop dangerously low, leading to symptoms such as nausea, headaches, confusion, and muscle weakness, and in severe cases, seizures. While rare, it is common among endurance athletes.

Therefore, it is generally more effective to drink water steadily in small amounts throughout the day rather than a large amount at once. It is recommended to set alarms every hour or use a water bottle with time markings to regulate your intake.

Myth 5: Drinking coffee or caffeinated tea can dehydrate you 

Truth: Dr. Bazilian emphasizes that "coffee and tea absolutely contribute to hydration," highlighting this as a widespread misconception. Ultimately, coffee and tea are made with water, so they have a hydrating effect. In the past, it was thought that the diuretic effect of caffeine caused dehydration, but recent studies show that at typical consumption levels, the diuretic effect is minimal and does not negatively impact overall fluid balance.

Similarly, the information that sparkling water causes dehydration is also incorrect. Sparkling water is just as effective as regular water for hydration, so feel free to drink it if you prefer it.

Myth 6: Sports drinks are better than water during exercise 

Truth: This depends on the duration, intensity, and environmental conditions of the exercise. According to Leslie Bonci, a sports dietitian who runs the health consulting firm Active Eating Advice, for short walks or exercise lasting less than an hour in cool weather, water alone is sufficient.

However, if you sweat a lot, engage in high-intensity exercise, or exercise for more than an hour, it's good to replenish electrolytes like sodium and potassium through low-sugar electrolyte powders. Sports drinks provide electrolytes and carbohydrates, helping to replenish energy lost during exercise and prevent muscle cramps. However, high-sugar sports drinks can lead to unnecessary calorie intake, so it's wise to choose low-sugar products or mix electrolyte powder with water.

Bonci emphasizes that hydration during exercise alone is not enough and that you should hydrate beforehand. "You should think of hydration as part of your internal equipment. Exercising while dehydrated makes you slower, weaker, and fatigue sets in faster," she explains. She recommends consuming about 0.6 liters of fluid an hour before exercise, stating that this is the time needed for the fluid to reach the muscles that will drive the exercise from the stomach. During exercise, it's good to take a few sips of fluid every 20 minutes to stay hydrated, and consume an additional 0.6 liters after exercise.

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