Health Library

Water in diet

Diet - water; H₂O

Water is a combination of hydrogen and oxygen. It is the basis for the fluids of the body.

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Function

Water makes up more than two-thirds of the weight of the human body. Without consuming water, most people would die in three to seven days. All the cells and organs need water to function.

Water serves as a lubricant. It makes up saliva and the fluids surrounding the joints. Water regulates the body temperature through perspiration. It also helps prevent and relieve constipation by moving food through the intestines.

Food Sources

You get some of the water in your body through the foods you eat. Some of the water is made during the process of metabolism.

You also get water through liquid foods and beverages, such as soup, milk, tea, coffee, soda, drinking water, and juices. Alcohol does not add to the body's water because it is a diuretic. It causes the body to release water.

Side Effects

If you do not get enough water each day, the body fluids will be out of balance, causing dehydration. When dehydration is severe, it can be life threatening.

Recommendations

The Dietary Reference Intake for water is between 91 and 125 fluid ounces (2.7 to 3.7 liters) of water per day for adults.

However, individual needs will depend on your sex, weight, age, and activity level, as well as any medical conditions you may have. Keep in mind that this is the total amount you get from both food and beverages every day. There is no specific recommendation for how much water you should drink.

If you drink fluids when you feel thirsty and have beverages with meals, you should get enough water to keep you hydrated. Try to choose water over sweetened drinks. These beverages can cause you to take in too many calories.

As you get older, your thirst may change. It is always important to take in fluids throughout the day. If you are concerned you may not be consuming enough water have a conversation with your health care provider.

Related Information

References

Cooney J, Neild P. Diet and nutrition. In: Court DS, Kadri A, Xiu P, eds. Medical Sciences. 4th ed. Philadelphia, PA: Elsevier; 2025:chap 16.

Hensrud DD. Diet and nutrition. In: Goldman L, Cooney KA, eds. Goldman-Cecil Medicine. 27th ed. Philadelphia, PA: Elsevier; 2024:chap 13.

Institute of Medicine of the National Academies. Dietary Reference Intakes for water, potassium, sodium, chloride, and sulfate (2005). National Academies Press. nap.nationalacademies.org/read/10925/chapter/2#5. Accessed July 22, 2025.

Review Date: 7/9/2025  

Reviewed By: Stefania Manetti, RDN, CDCES, RYT200, My Vita Sana LLC - Nourish and heal through food, San Jose, CA. Review provided by VeriMed Healthcare Network. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

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