The role of water is most important in the entire structure and functioning of the human body. About 60 to 70 percent of our body is made up of water only. From the brain's ability to think to muscle functioning, joint lubrication, digestion, elimination of toxins and blood circulation, every basic process depends on water. In today's busy life, most of the people keep drinking tea, coffee or packaged drinks throughout the day, but ignore the required amount of pure water. On the other hand, some people who are very health conscious put extra pressure on their kidneys by drinking more water than required throughout the day. In such a situation, this question comes up again and again that how much water should a healthy person drink in a day? Is the traditionally believed rule of '8 glasses of water' scientifically correct or do the body's needs differ from person to person? Let us understand in detail the correct mathematics of water according to modern medical science, World Health Organization (WHO) and nutritionists. The 8 Glass Water Rule: Scientific Truth or Just a Popular Myth? Since childhood, we all have been hearing that we must drink at least 8 glasses of water (about 2 liters) daily. This is called the '8×8 rule' in the health world. Although this rule may be a general guideline according to modern medical science, it does not apply equally to every person. Scientists believe that every person's physical structure, daily routine, nature of work, living environment and metabolic rate are different. For example, the water requirement of a person who works for 8 hours sitting in an air-conditioned office and a laborer who sweats in the sun and heat and does physical labor can never be the same. Therefore, it is not completely scientifically correct to accept a certain figure as mandatory for everyone. What is the right amount of water per day according to age, gender and weight? According to the guidelines of the US National Academy of Sciences, Engineering and Medicine (NASEM) and the Indian Council of Medical Research (ICMR), the daily requirement of water and fluids for a healthy adult in normal weather is as follows: Adult male: An average of 3.5 to 3.7 liters of fluids per day (about 13 to 15 cups). Adult women: Average 2.5 to 2.7 liters of fluids per day (about 9 to 11 cups). Pregnant and lactating women: 500 to 700 ml more water than usual i.e. about 3 to 3.5 liters per day. Children (4 to 13 years): 1.5 to 2.2 liters per day (depending on age and activity). Elderly (over 60 years): At least 2 to 2.5 liters per day, as the natural feeling of thirst weakens with age. A simple formula to find your correct dose based on weight is to divide your total weight (in kilograms) by 30. For example, if you weigh 60 kg, then 60/30 = 2 liters. To this, half to one liter additional water should be added depending on the daily physical exertion. Not just plain water, the body also gets hydration from these foods. About 20 percent of the total water we consume comes from solid and liquid foods, while the remaining 80 percent comes from direct water and other healthy beverages. If you get bored of drinking just plain water, you can include these high water-content foods in your diet: Cucumber: These contain about 95 to 96 percent water, which cools the stomach and replenishes electrolytes. Watermelon and Muskmelon: Rich in 92 percent water, these seasonal fruits give instant energy and hydration to the body. Coconut water: A natural electrolyte drink rich in potassium, magnesium and sodium that provides instant protection from dehydration. Buttermilk and Lemon Water: Rich in probiotics and Vitamin C, this drink helps in maintaining water balance in the body while keeping the digestion process healthy. Tomato, bottle gourd and ridge gourd: The natural juice present in green vegetables keeps the body internally hydrated. 6 hidden signs of lack of water in the body: Recognize dehydration in time. When the water level in the body starts decreasing, the body starts giving many subtle and hidden warning signals even before feeling thirsty: Dark yellow color of urine: The easiest and most accurate way to check hydration is the color of urine. If the color of urine is light transparent or light yellow like lemon then the body is fully hydrated. Dark yellow or brown color indicates severe water deficiency. Heaviness in the head and brain fog: 75 percent of the brain is made up of water. Even slight dehydration can cause headaches, irritability, difficulty concentrating and mental dullness. Dryness of skin and lips: Dry skin, cracked lips and burning sensation in the eyes are the result of internal dehydration. Constant craving for sweets: When the body is dehydrated, the liver is hampered in releasing glycogen, which the brain mistakes as hunger or sugar cravings. Bad breath: Due to lack of water, the production of saliva decreases, due to which bacteria start growing in the mouth and bad breath starts. Muscle cramps: When electrolytes and water are lost through sweat, the muscles in the legs and calves suddenly experience severe pain and strain. Can drinking too much water be harmful? Know the danger of 'water intoxication'. In order to get health benefits, many people make the mistake of drinking 5 to 6 liters of water without feeling thirsty. According to medical experts, drinking more water than required can prove fatal for the body. This condition is called 'Hyponatremia' or 'water intoxication' in medical language. When we drink too much water in a short period of time, our kidneys become unable to expel the excess water. This results in blood sodium levels becoming dangerously thin and low. Due to lack of sodium, the cells of the body and especially the brain start swelling. Symptoms include nausea, vomiting, severe headache, seizures, and in severe cases, the risk of coma or even death. Therefore, always drink water according to your thirst and physical needs. Ayurveda and Modern Science: 5 Golden Rules of Drinking Water It is not enough to know only how much water to drink, but how and when to drink it is equally important: Lukewarm water (Ushapan) on an empty stomach in the morning: Drinking 1 to 2 glasses of lukewarm water after waking up in the morning flushes out the toxins accumulated in the intestines overnight and activates the metabolism. Drink while sitting and sip: Never drink water while standing or by sipping from the bottle. By sitting quietly and drinking water sip by sip, the saliva in the mouth mixes with the water and balances the acid in the stomach. Do not drink cold water immediately after eating: Drinking very cold or too much water immediately after eating slows down the digestive fire of the stomach and the food starts rotting instead of being digested. Drink water at least 40 to 45 minutes after meals. Balance during and after workout: Do not drink a lot of water at once while exercising. Just sip one or two sips of water every 15 to 20 minutes and drink enough water 15 minutes after the workout is over. Avoid excessively chilled water: Instead of extremely cold water from the fridge, drink pot water or normal temperature water, which is safe for the nerves of the throat and digestive system. Water is not an ordinary drink but the lifeline of our body. Listen to your body's signals, understand your hydration status by looking at your color and drink balanced amounts of water at the right time to keep yourself healthy, energetic and refreshed throughout the year.