"In our daily lives, water is so commonplace that it's often overlooked. Yet precisely because of this, most people remain unaware of how much water they should drink daily, what kind of water is best, and when to drink it... and this directly impacts our health," Professor Cheng Yiyong, Vice Chairman of the Chinese Nutrition Society, told Life Times.To address this, we invited Professor Li Li, Deputy Director of the National Food and Nutrition Advisory Committee and Professor at the College of Food Science and Nutrition, China Agricultural University; Wang Yi, Director of the Department of Dietary Therapy and Nutrition at Guang'anmen Hospital, China Academy of Chinese Medical Sciences; and Professor Cheng Yiyong to answer 10 critical questions about water consumption that are closely tied to health and of great public concern. Next, we'll delve into whether it's safe to drink water left overnight.
Question 1: What nutrients are actually in water?Li Li: Many people do wonder if water contains various nutrients, yet they overlook a fundamental fact—water itself is a nutrient. We often talk about the six major nutrients the human body needs: carbohydrates, fats, proteins, vitamins, minerals, and water. Water is the essence of life, an indispensable nutrient for the survival of both animals and plants.Moreover, water constitutes the most abundant component in the human body. With sufficient water intake, a person can survive for weeks without food; however, without water, death occurs within days. Therefore, whether you prefer plain water, tea, or soup, daily consumption of adequate "water nutrients" is essential to keep this complex machine—the human body—functioning properly.
Question 2: Is plain water the most effective for hydration?
Cheng Yiyong: This view is somewhat one-sided. Plain water is indeed effective for hydration, but its plain taste may make it seem "unpleasant" to some. Studies indicate that people tend to consume more fluids when drinking beverages they enjoy.
The latest edition of the Chinese Dietary Guidelines by the Chinese Nutrition Society also notes that the vast majority of beverages on the market contain over 80% water.The primary function of beverages is to replenish the body's water needs while providing consumers with a pleasant taste experience. However, many beverages contain calories, meaning hydration comes with increased caloric intake. Therefore, portion control is essential when consuming drinks like cola. Beyond plain water, options like a glass of milk in the morning or juice between meals are also good choices.
Third Question: What are the nutritional differences between plain water, purified water, and mineral water?
Li Liti: Composition-wise, both boiled water and mineral water contain minerals, while purified water is simply pure water. In northern China, like Beijing, kettles often develop thick mineral deposits on their inner walls—this mineral presence makes boiled water a form of mineral water. But does this mean mineral-rich water is inherently better?Not necessarily. After all, the mineral content in water is very low and does not significantly impact the body's mineral intake. Therefore, it is incorrect to claim that long-term consumption of mineral water leads to excessive mineral intake or even poisoning, just as it is incorrect to say that long-term consumption of purified water causes nutritional deficiencies.
Question 4: Can drinking soup hydrate you?
Cheng Yiyong: Absolutely. Since over 90% of soup is water, it is an excellent way to hydrate.However, soups should not be overly salty. Excessive sodium intake alters the body's osmotic pressure, forcing us to drink more water to balance it—which is why soup sometimes makes us feel thirstier. When preparing soups, salt should be strictly controlled. Broths made from chicken or mushrooms are naturally flavorful and can be enjoyed without added salt.
Question 5: Is it safe to drink water left overnight?
Li Li: While some microorganisms may multiply in overnight water, the harm to the human body isn't as severe as some claim. As long as it hasn't been contaminated, the water's properties remain unchanged, so drinking it overnight poses no significant issue. The spring water we drink today likely originated tens of thousands of years ago.
Question 6: Is it safe to drink water that's been boiled multiple times?
Wang Yi: Some refer to this as "thousand-boil water," meaning water repeatedly heated in water dispensers or kettles. Generally, such water contains higher levels of nitrites. Large amounts of nitrites can cause direct poisoning because they react with human blood to form methemoglobin, which impairs the blood's oxygen-carrying capacity, leading to oxygen deprivation and poisoning.While nitrite levels in repeatedly boiled water may not reach such high concentrations, nitrites are carcinogenic, teratogenic, and mutagenic substances when ingested in sufficient quantities, posing serious health risks. Therefore, avoid repeatedly boiling water whenever possible. For water dispensers, it's best to boil water "as needed" rather than leaving it in a constant "heat-preserve" state.
Question 7: Is water's pH level truly important?
Li Liti: In the 1990s, Japan developed electrolyzed water—a process using electrodes to treat water into acidic water for sterilization and alkaline water for health benefits. Both types were recognized by Japan's Ministry of Health and Welfare.However, alkaline water must have a pH level above 8.5 to effectively reduce stomach acid and regulate intestinal flora. Certain waters marketed as "weakly alkaline" claim to alter the body's acid-alkaline balance, which is impossible and largely conceptual hype.
Question 8: Can drinking water detoxify the body?
Li Liti: First, what exactly is "detoxification"? To this day, no one has clearly defined this concept. However, the human body requires water for metabolism. Drinking more water can promote gastrointestinal motility and ease bowel movements. From this perspective, it is correct to say that drinking more water can aid detoxification.
Question 9: What exactly is the "eight glasses of water" daily requirement?
Cheng Yiyong: This question troubles many because cup sizes vary. Our new dietary pyramid includes a water icon to emphasize adequate hydration. For adults with light physical activity in temperate climates, at least 1200 milliliters daily—equivalent to two bottles of mineral water—is recommended.Some may ask: Why has the recommendation dropped from the previous guideline of at least 2000 milliliters per day to just 1200 milliliters? In fact, 2000 milliliters refers to the total daily water requirement. Fruits and vegetables contain substantial amounts of water, and even staple foods and meat contribute hydration. A significant portion of the water our bodies need comes from the foods we eat.
Question 10: How should we drink water upon waking and before bed?
Wang Yi: The first glass of water in the morning is like lifesaving water. After a night of metabolic activity, the body needs to flush out all waste products.Our cells act like dry sponges—they absorb water upon intake and expel it within about 40 minutes. This metabolic process is the detoxification we seek. For this morning water, choose one of these three options: First, clear water—boiled water, purified water, or mineral water—which reduces blood viscosity.Second, lemon water. Citric acid boosts morning appetite, and its small molecular size doesn't burden kidney metabolism, promoting urination. Third, lightly salted water, which is highly beneficial for those with constipation.
For evening hydration, honey water, milk, or yogurt are suitable options. However, those concerned about nighttime bathroom trips should avoid drinking water right before bed. Additionally, after getting up at night, you may drink a glass of water; if you didn't get up, you can drink it in the morning instead.
Can you drink water left overnight? That concludes our introduction. We hope this information proves helpful. Finally, we wish you good health and smooth sailing this winter.