Coffee as Good as Water for Hydration

Coffee in moderation keeps the body as hydrated as drinking normal water

/ Author:  / Reviewed by: Joseph V. Madia, MD Beth Bolt, RPh

(RxWiki News) If you ever worried about your morning coffee leaving you dehydrated, the results of a new study may put you at ease.

This new study set out to determine the effects, if any, that caffeinated drinks have on hydration.

The researchers looked at hydration levels of men who consumed moderate amounts of coffee and compared them to men drinking equal amounts of water.

This study showed that coffee drinkers maintained the same level of hydration as their water drinking counterparts.

"Stay hydrated throughout the day."

This study was led by Sophie C. Killer, of the School of Sport and Exercise Sciences at the University of Birmingham in the United Kingdom.

The researchers set out to reexamine a 1928 study that showed caffeine to have a diuretic effect, leaving many to believe that consuming coffee could lead to dehydration.

These researchers looked at 52 healthy, non-smoking males between the ages of 18 and 46 who were moderate coffee drinkers consuming three to six cups a day. All of the study subjects met a long list of criteria such as stable weight and a basic diet free of extreme food or beverage consumption to ensure the most accurate results possible.

This study did not include women due to possible disruptions to fluid balance by the menstrual cycle.

The investigators randomly assigned half of the participants to drink four cups of black coffee for three consecutive days while the other half drank the same quantity of water during the same period.

The researchers gave the men a 10-day break and the groups switched roles — the water drinkers changed to coffee and coffee drinkers began the water routine.

The research team controlled each group’s diet by providing meals to participants, and activities such as drinking alcohol or physical activity were stopped at least 24 hours prior to the beginning of the trial.

The researchers used body mass, total body water and blood and urine tests to evaluate the hydration level of each participant.

This research showed that both groups lost a small amount of body mass (0.2 percent reduction) but never came close to the 1 to 3 percent loss where dehydration is diagnosed.

The researchers saw no changes or differences in the blood work between the coffee and the water drinking groups. The blood tests included total plasma protein, sodium and potassium.

The researchers also found no difference in the total volume of urine from each participant.

These researchers concluded that drinking a moderate amount of coffee, among men who were used to drinking coffee, provided the same level of hydration as an equal amount of water, and did not negatively affect fluid balance.

"Coffee is predominantly water! Therefore, it should come as no surprise that studies have found that coffee is hydrating. It's the caffeine in the coffee that can be dehydrating!" said Dr. Mark Mincolla, legendary health care practitioner and author of "WHOLE HEALTH: A Holistic Approach to Healing for the 21st Century" and dailyRx Contributing Expert.

"Researchers have established that a dose of caffeine in excess of 500 mg can dehydrate! The average cup of generic home brewed coffee contains between 95-200 mg of caffeine. De-caf contains 8.6-13.9 mg of caffeine. So, either limit your coffee intake to 1-2 cups, or hydrate with decaf!" he said.

This study was published online January 9 on PLoS ONE.

Funding for this study was provided by the Institute for Scientific Information on Coffee.

Asker E. Jeukendrup disclosed the he is currently employed by PepsiCo Inc.

Review Date: 
January 10, 2014
Last Updated:
March 12, 2015