Coffee

Is coffee or tea a diuretic?

Pawel Malczewski
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Short summary

There is no scientific evidence that drinking coffee, tea or iced tea causes dehydration. On the contrary, the studies have shown that, if consumed on regular basis, caffeinated beverages such as coffee or tea do not make you urinate more and so can be counted towards the daily fluid intake. For a quick answer click here.

Explanation

Is coffee or tea a diuretic?

Studies have shown that drinking 2-3 cups of coffee or 5-8 cups of tea or iced tea of standard amount of caffeine per day have no diuretic effect. (1)Maughan RJ, Griffin J. Caffeine ingestion and fluid balance: a review. J Hum Nutr Diet. 2003 Dec;16(6):411-20. Available here. (2)Grandjean AC, Reimers KJ, Bannick KE, Haven MC. The effect of caffeinated, non-caffeinated, caloric and non-caloric beverages on hydration. J Am Coll Nutr. 2000 Oct;19(5):591-600. Available here.

A study on habitual male coffee drinkers has shown that drinking 4 cups of coffee per day has a similar hydrating effect as water. (3)Killer SC, Blannin AK, Jeukendrup AE. No evidence of dehydration with moderate daily coffee intake: a counterbalanced cross-over study in a free-living population. PLoS One. 2014 Jan 9;9(1):e84154. Available here.

Another study showed that taking 4-6 cups of black tea (equivalent to 168 – 252 mg of caffeine) had the same hydrating results as drinking the same amount of water. (4)Ruxton CH, Hart VA. Black tea is not significantly different from water in the maintenance of normal hydration in human subjects: results from a randomised controlled trial. Br J Nutr. 2011 Aug;106(4):588-95. Available here.

However, people who have not been drinking tea, iced tea, coffee or other caffeinated drinks for some time (days to weeks depending on a person), react temporarily to high amount of caffeine.

It has been found that, in these cases, drinks with large doses of caffeine (250-300mg which is about double of a standard, but strong coffee) can increase urination. This increase, however, is only a temporary reaction to caffeine after long abstinence. Once the body accustoms itself to regular coffee intake of standard caffeine contents, the water loss from the body is insignificant. (5)Maughan RJ, Griffin J. Caffeine ingestion and fluid balance: a review. J Hum Nutr Diet. 2003 Dec;16(6):411-20. Available here. (6)Grandjean AC, Reimers KJ, Bannick KE, Haven MC. The effect of caffeinated, non-caffeinated, caloric and non-caloric beverages on hydration. J Am Coll Nutr. 2000 Oct;19(5):591-600. Available here.

Popular drinks contain various amounts of caffeine. Here is a breakdown of the standard amount of caffeine in most popular drinks and chocolate. (7)FDA. U.S. Food and Drug Administration. Caffeine and your body. Available here. 

Caffeine contents of various foods and drinks

ProductCaffeine (mg)
Coffee (5 oz. or 150 ml)60-150
Tea (5 oz. or 150 ml)40-80
Green tea (8 oz.)15
Decaf coffee2-5
Red Bull (8 oz.)80
Soft drinks such as Coke/Diet Coke/Pepsi (12 oz.)30-55
Dark chocolate 1 oz. (28g)20
Hot chocolate (5 oz. or 150 ml)5-20

Is decaf coffee dehydrating?

The myths of coffee or tea being a diuretic exists because caffeine was believed to cause increased urination. Decaf coffee contains very small amounts of caffeine so there are no reasons to think that decaf coffee is dehydrating.

Conclusion

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Coffee, green tea, black tea or iced tea are not diuretic. If you are not accustomed to drinking caffeinated drinks or had a long period of abstinence, insure that you drink extra water with high caffeinated drinks in order to compensate for the temporary water loss trough your body. Otherwise drinking coffee or tea will hydrate rather than dehydrate you.

References   [ + ]

1. Maughan RJ, Griffin J. Caffeine ingestion and fluid balance: a review. J Hum Nutr Diet. 2003 Dec;16(6):411-20. Available here.
2. Grandjean AC, Reimers KJ, Bannick KE, Haven MC. The effect of caffeinated, non-caffeinated, caloric and non-caloric beverages on hydration. J Am Coll Nutr. 2000 Oct;19(5):591-600. Available here.
3. Killer SC, Blannin AK, Jeukendrup AE. No evidence of dehydration with moderate daily coffee intake: a counterbalanced cross-over study in a free-living population. PLoS One. 2014 Jan 9;9(1):e84154. Available here.
4. Ruxton CH, Hart VA. Black tea is not significantly different from water in the maintenance of normal hydration in human subjects: results from a randomised controlled trial. Br J Nutr. 2011 Aug;106(4):588-95. Available here.
5. Maughan RJ, Griffin J. Caffeine ingestion and fluid balance: a review. J Hum Nutr Diet. 2003 Dec;16(6):411-20. Available here.
6. Grandjean AC, Reimers KJ, Bannick KE, Haven MC. The effect of caffeinated, non-caffeinated, caloric and non-caloric beverages on hydration. J Am Coll Nutr. 2000 Oct;19(5):591-600. Available here.
7. FDA. U.S. Food and Drug Administration. Caffeine and your body. Available here.

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