7 science-backed benefits of drinking water - and how much water you should drink each day

woman drinking water — Staying hydrated is important for regulating your body temperature and prevent heatstrokes.
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The benefits of drinking water include improving the appearance of the skin, preventing joint pain, and even helping with weight loss.
Drinking water can also improve cognitive functioning by preventing fatigue, short-term memory loss, and trouble focusing.
Men should drink about 3.7 liters of water a day and women about 2.7 liters of water a day — though exactly how much water you should drink depends on a variety of factors, like how much you exercise.
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Water plays a major role in the function of nearly every system in the body, from helping regulate body temperature to lubricating and cushioning your joints. Here are seven health benefits of drinking water and how much you need to drink each day.

1. Can help with weight loss

When incorporated as part of a weight loss plan, drinking water, especially before meals, can help shed extra pounds, says Rajnish Jaiswal, MD, emergency medicine physician with NYC Health + Hospitals Metropolitan.

One reason for this is because water increases satiety by helping you feel full, which then may result in consuming fewer calories.

In a small 2010 study, dieters between the ages of 55 and 75 on a caloric deficit who drank 16.9 ounces of water before meals lost 44% more weight than dieters who didn’t drink water before meals over a 12 week period. Another small 2013 study of women between the ages of 18 and 23 found drinking an additional 16.9 ounces of water half an hour before meals for eight weeks resulted in significant reductions in body fat and body weight.

Drinking water can also help you lose weight because proper hydration allows you to recover faster from exercise and slightly boosts your metabolism, Jaiswal says.

2. Cushions joints

Water plays an important role in joint health by keeping joints lubricated and cushioned. Synovial fluid, which reduces friction in joint cartilage, is mostly made of water. Therefore, low water consumption can contribute to joint pain.

Less fluid in joints can cause friction, increasing inflammation, which can worsen joint pain, especially for people with arthritis. Staying properly hydrated can reduce joint pain in general, Jaiswal says, but for people with arthritis, hydrogen water may offer more benefits.

A small 2012 study found drinking 18 ounces of water with a high concentration of molecular hydrogen (water with additional hydrogen gas dissolved into it) for four weeks significantly reduced joint pain and oxidative stress (a marker of inflammation) in people with rheumatoid arthritis.

3. Boosts skin health

Adequate water intake also keeps skin lubricated and supple, Jaiswal says.

"Skin with normal turgor (elasticity) when pinched snaps rapidly back to its normal position," Jaiswal says. "Dehydrated skin takes time to return to its normal position. When skin cells lose water, they become shriveled and less elastic, leading to creases and wrinkles."

A small 2015 study of women found increased water consumption was associated with better skin hydration and appearance. However, drinking water alone isn't enough to ensure healthy skin, as diet and genetics will also play a role.

4. Regulates body temperature

Hydration is critical to regulating body temperature, says Nate Favini, MD, medical lead of Forward, a preventive primary care practice. Sweating is your body's primary method of cooling itself. Dehydration inhibits your ability to produce enough sweat, making it difficult to properly regulate body temperature.

Dehydration is a risk factor for heat-related illnesses like heatstroke, which can be fatal. A 2010 review found recovery from dehydration in older adults is longer than in younger people, which exacerbates their risk of heat-related injuries.

If you are sweating a lot, either because of warm weather or physical activity, you should drink plenty of water to reduce your risk of overheating, Favini says.

5. Improves athletic performance

Inadequate water intake can also make exercise feel more difficult and reduce your performance, Jaiswal says. According to a 2010 review, athletes can lose 6% to 10% of their body weight through sweat during exercise, and performance is affected at just 2%.

"Water is absolutely crucial in the pursuit of athletic excellence," Jaiswal says. "Dehydration may lead to some adverse results such as decreased muscle endurance and strength. Without adequately replacing [fluids], the body just cannot sustain elite athletic performance and hence will cause the athlete to slow down."

Just how much water you should drink before, during, and after exercise depends on many factors, but in general, the American Council on Exercise recommends drinking:

17 to 20 ounces of water two to three hours before you start exercising
8 ounces of water 20 to 30 minutes before you start exercising
7 to 10 ounces of water for every 10 to 20 minutes of exercise

6. Prevents constipation

Water helps your body flush out waste, both through urine and bowel movements. According to a 2015 study, low water consumption can be a risk factor for constipation in people over the age of 65.

Drinking water can help soften stools and stimulate bowel movements. Consuming foods high in magnesium and fiber - like whole grains, fruits, and vegetables - may also help ease constipation.

7. Helps with brain functioning

The brain operates by sending electrical signals across nerves. Without adequate water and electrolyte levels, your body's cells are unable to receive those signals.

Inadequate water consumption can alter brain function and lead to:

Fatigue
Trouble focusing
Decreased retention time
Loss of short-term memory
Confusion

Mild dehydration can also impair your mood and concentration. In a small 2011 study, researchers found fluid loss of 1.4% after exercise in young women resulted in decreased mood, impaired concentration, and increased frequency of headaches.

How much water should you drink each day?

The amount of water you need to drink each day varies depending on your age, weight, and activity level. Generally speaking, the U.S. National Academies of Sciences, Engineering and Medicine recommends:

3.7 liters of water a day for adult males
2.7 liters of water a day for adult females

This is just a general recommendation, and you may need to drink more depending on additional factors, Favini says. Some of these factors include:

Level of physical activity
Illness - specifically one that causes loss of fluids through vomiting or diarrhea
Climate - for example, if you live in a hot, humid, or dry climate, you need more water
Altitude - those at higher altitudes require more water

Though uncommon, it is possible to consume too much water, which can cause an electrolyte imbalance. This electrolyte imbalance can lead to a condition of low sodium known as hyponatremia, which can be fatal. Signs of overhydration include:

Nausea
Malaise, or a general feeling of discomfort
Headache
Lethargy
Confusion

Overhydration most commonly occurs in athletes who are drinking water without electrolytes, Favini says. To prevent this while exercising for prolonged periods, try to drink two to four cups of fluid per hour and include electrolytes in your fluid replacement by consuming a sports drink with electrolytes or pedialyte.

Insider's takeaway

Water is critical to several functions in the body, and drinking adequate amounts of water can improve your health. The amount of water you need each day varies by person, but a good rule of thumb is to increase your water intake before and after exercising and also when the weather is warm or humid.