Drinking plenty of water supports hydration, digestion, kidney function, energy, and skin health.
Benefits
- Hydration and temperature control.
- Better digestion and fewer constipation issues.
- Kidney function and fewer kidney stones.
- Energy and focus: even mild dehydration lowers mood.
- Skin and joint lubrication.
How much
About 3.7 L a day for men and 2.7 L for women, from all drinks and food.
Signs of enough
Pale yellow urine.
Caution
Too much can cause hyponatremia.
Hydration numbers
The National Academies set adequate total water intake at about 3.7 liters per day for men and 2.7 liters for women, including food, which supplies roughly 20 percent. That means about 13 cups of beverages for men and 9 cups for women. Needs rise with heat, exercise, pregnancy and breastfeeding.
- A 2018 review linked adequate hydration to better kidney stone prevention, and doctors advise producing at least 2.5 liters of urine per day for stone formers.
- Mild dehydration of 1 to 2 percent of body weight can impair concentration and mood.
- Water has no calories and replacing sugary drinks lowers calorie intake.
Signs and caution
Pale yellow urine is a simple marker of good hydration. Drinking far beyond thirst offers no extra benefit and can be dangerous in extreme volumes, causing hyponatremia. People with heart failure or kidney disease may be on fluid limits and should follow medical advice. Coffee, tea, milk and fruits also contribute to fluid intake.
Hydration numbers
The National Academies suggest total water intake from all drinks and food of about 3.7 liters for men and 2.7 liters for women daily. Water supports temperature control, joint lubrication and kidney function. A 2018 study in Annals of Family Medicine linked increased water intake with lower risk of kidney stones, and the usual advice is to produce about 2 to 2.5 liters of urine a day.
Signs and caution
Pale yellow urine suggests good hydration. Too much water can cause hyponatremia. Needs rise with heat, exercise, pregnancy and illness. People with heart or kidney failure may be given fluid limits.
Physiology of water
Water makes up about 60 percent of adult body weight. A 2 percent loss of body water reduces cognitive performance, mood and exercise capacity, according to reviews. Water supports kidney function, and higher intake lowers urinary tract infection recurrence in women, shown in a 2018 JAMA Internal Medicine trial of 140 women who drank 1.5 extra liters daily.
Practical advice
About 20 percent of water comes from food. Drink more in heat, exercise, fever, pregnancy and breastfeeding. Water does not guarantee weight loss, though drinking 500 mL before meals reduced intake in some trials. Thirst, urine color and body weight changes guide hydration. People with heart failure or kidney failure follow their doctor’s fluid limits.
Based on data from the National Academies of Sciences and JAMA Internal Medicine
