Eight cups a day is such a persistent myth that you might think you know the answer to this question. But the fact is, how much water you need to drink each day depends on a few factors, including your age, gender, activity level and even the weather. The Institute of Medicine, which sets Dietary Reference Intakes for all nutrients, says that in general, women need around 11 cups of water a day, while men need 15.6 cups a day.
Does that mean I need to guzzle water all day long?
Those 11-16 cups a day include all liquid in your diet, so if you’re envisioning needing to sip water nonstop to meet the requirement, don’t worry. All the liquids you drink — including tea, juice, coffee and soda (not that you’re drinking soda, right?) — give you some of the water you need each day. Even a beer will hydrate you, although multiple alcoholic beverages or hard alcohol act as a diuretic. You can also hydrate through many of the foods you eat. Soup is obviously hydrating, but so are foods with a high water content, like cucumbers, lettuce or watermelon (find more hydrating foods here).
Any other factors to consider?
- Exercise: If you’ve been sweating a lot (like after a long, hard workout), you need more than just water to rehydrate you. When you sweat you also lose electrolytes, such as sodium, chloride, calcium, magnesium and potassium. So if you’ve been working out for over an hour, make sure you get some salt back in you, either through a snack (like a handful of pretzels) or a recovery beverage (studies have shown that milk, which delivers both sodium and protein, makes an excellent recovery beverage). If you’re exercising for less than an hour, plain water is just fine — you don’t want to undo all those calories burned with a sugary sports drink.
- Weather: You need to drink more water if you’re in a hot environment. High humidity also increases your water needs, so make sure you drink enough water and eat water-rich foods when it’s hot out, especially if you’re exercising.
- Weight loss: Water fills you up — it’s one of the reasons eating water-rich, low-calorie foods can help you feel satisfied and ultimately slim down. In a 2010 study, older adults who drank 2 cups of water before meals lost a few more pounds over 4 months than those who didn’t drink water first.