Nutrition and healthy eating

How much water should you drink each day? It's a simple question with no easy answer.

Studies have produced varying recommendations over the years. But your individual water needs depend on many factors, including your health, how active you are and where you live.

No single formula fits everyone. But knowing more about your body's need for fluids will help you estimate how much water to drink each day.

What are the health benefits of water?

Water is your body's principal chemical component and makes up about 50% to 70% of your body weight. Your body depends on water to survive.

Every cell, tissue and organ in your body needs water to work properly. For example, water:

• Gets rid of wastes through urination, perspiration and bowel movements
• Keeps your temperature normal
• Lubricates and cushions joints
• Protects sensitive tissues

Lack of water can lead to dehydration — a condition that occurs when you don't have enough water in your body to carry out normal functions. Even mild dehydration can drain your energy and make you tired.

How much water do you need?

Every day you lose water through your breath, perspiration, urine and bowel movements. For your body to function properly, you must replenish its water supply by consuming beverages and foods that contain water.

So how much fluid does the average, healthy adult living in a temperate climate need? The U.S. National Academies of Sciences, Engineering, and Medicine determined that an adequate daily fluid intake is:

• About 15.5 cups (3.7 liters) of fluids a day for men
• About 11.5 cups (2.7 liters) of fluids a day for women

These recommendations cover fluids from water, other beverages and food. About 20% of daily fluid intake usually comes from food and the rest from drinks.

What about the advice to drink 8 glasses a day?

You've probably heard the advice to drink eight glasses of water a day. That's easy to remember, and it's a reasonable goal.

Most healthy people can stay hydrated by drinking water and other fluids whenever they feel thirsty. For some people, fewer than eight glasses a day might be enough. But other people might need more.

You might need to modify your total fluid intake based on several factors:

• Exercise. If you do any activity that makes you sweat, you need to drink extra water to cover the fluid loss. It's important to drink water before, during and after a workout.
• Environment. Hot or humid weather can make you sweat and requires additional fluid. Dehydration also can occur at high altitudes.
• Overall health. Your body loses fluids when you have a fever, vomiting or diarrhea. Drink more water or follow a doctor's recommendation to drink oral rehydration solutions. Other conditions that might require increased fluid intake include bladder infections and urinary tract stones.
• Pregnancy and breast-feeding. If you are pregnant or breast-feeding, you may need additional fluids to stay hydrated.

Is water the only option for staying hydrated?

No. You don't need to rely only on water to meet your fluid needs. What you eat also provides a significant portion. For example, many fruits and vegetables, such as watermelon and spinach, are almost 100% water by weight.

In addition, beverages such as milk, juice and herbal teas are composed mostly of water. Even caffeinated drinks — such as coffee and soda — can contribute to your daily water intake. But go easy on sugar-sweetened drinks. Regular soda, energy or sports drinks, and other sweet drinks usually contain a lot of added sugar, which may provide more calories than needed.

How do I know if I'm drinking enough?

Your fluid intake is probably adequate if:

• You rarely feel thirsty
• Your urine is colorless or light yellow

Your doctor or dietitian can help you determine the amount of water that's right for you every day.

To prevent dehydration and make sure your body has the fluids it needs, make water your beverage of choice. It's a good idea to drink a glass of water:

• With each meal and between meals
• Before, during and after exercise
• If you feel thirsty

Should I worry about drinking too much water

Drinking too much water is rarely a problem for healthy, well-nourished adults. Athletes occasionally may drink too much water in an attempt to prevent dehydration during long or intense exercise. When you drink too much water, your kidneys can't get rid of the excess water. The sodium content of your blood becomes diluted. This is called hyponatremia and it can be life-threatening.