Is Caffeine Considered a Diuretic?

Because of the diuretic effect of caffeine on the reabsorption of water in the kidney, it was previously thought that the consumption of caffeinated beverages, could lead to a total body water deficit.

Although slight variations have existed, the prevalent message has been that eight 8-oz glasses of water will assure hydration and that caffeinated beverages should be excluded or the volume significantly reduced when assessing fluid intakes. However, as early as 1928, it was reported that caffeine-containing beverages did not significantly increase 24-hour urinary output.

In 2005, the Dietary Reference Intake guideline for water was published. The Adequate Intake (AI) for total water, which includes water from food and beverages, was determined to be 3.7 liters (L) and 2.7 L per day for men and women (ages 19 and older), respectively. The report went on to say that the contribution of caffeinated beverages to the daily total water intake appears to be similar to the contribution of noncaffeinated beverages.

A 2015 meta-analysis investigated caffeine intake in healthy adults, which ranged from a minimum of 114 milligrams (mg) to a maximum of 741 mg with a median intake of 300 mg. Researchers found that caffeine consumption resulted in only mild diuresis but not following exercise and was higher in female participants.

Although caffeine consumption may not pose a threat relative to hydration status, it is considered a safety concern especially for children and adolescents and when consumed in excessive amounts. Several natural sources of caffeine exist, but it also may be added to foods, beverages, dietary supplements and even medications. As a result, products such as energy drinks may be marketed as beverages or as dietary supplements resulting in different product labeling requirements.

The 2020-2025 Dietary Guidelines for Americans refer to the U.S. Food and Drug Administration's limit of 400 mg of caffeine per day as a safe intake for healthy adults, since that amount is "not generally associated with dangerous, negative effects." It is also recommended to limit caffeine intake while breastfeeding to 300 milligrams or less per day.

However, there is no amount of caffeine that is considered to be safe for young children. Although the DGAs indicate that caffeine should be avoided by children under the age of 2, the "Healthy Drinks, Healthy Kids – Consensus Beverage Guidelines for Children", which originated from a collaboration that included the Academy, recommend that children 5 and under avoid drinks containing caffeine.

The bottom line is that most adults do not need to avoid caffeine if consumed in moderate amounts and that caffeinated beverages do contribute to the daily water requirements in a manner similar to other fluids.

References:

• U.S. Department of Agriculture and U.S. Department of Health and Human Services. Dietary Guidelines for Americans, 2020-2025. 9th Edition. December 2020. Available at DietaryGuidelines.gov.
• Institute of Medicine. Dietary Reference Intakes for water, potassium, sodium, chloride, and sulfate. 2005. The National Academies Press Web site. Available online. Accessed November 19, 2021.
• Kraak VI, Davy BM, Rockwell MS, Kostelnik S, Hedrick VE. Policy Recommendations to Address Energy Drink Marketing and Consumption by Vulnerable Populations in the United States. J Acad Nutr Diet. 2020 May;120(5):767-777. Accessed August 24, 2021.
• Zhang Y, Coca A, Casa DJ, Antonio J, Green JM, Bishop PA. Caffeine and diuresis during rest and exercise: A meta-analysis. J Sci Med Sport. 2015;18(5):569-574. doi:10.1016/j.jsams.2014.07.017
• Healthy Eating Research. Technical Scientific Report. Healthy Beverage Consumption in Early Childhood: Recommendations from Key National Health and Nutrition Organizations. September 2019. Accessed December 1, 2021.