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Are your favourite caffeinated drinks dehydrating you?

29 Nov 2022


You may have heard that caffeinated beverages aren’t ashy drating as plain water and might even have the potential to make you dehydrated. If you’re a coffee or tea lover, you’re probably keen to know if there is any truth in this - so we take a look at the evidence.

Does caffeine make you lose water?

Caffeine acts as a mild diuretic, which means that drinks such as coffee, tea and energy drinks might encourage you to urinate more than a caffeine-free beverage would. More frequent urination causes your body to lose water, although there are conflicting reports as to whether it’s the caffeine that is stimulating this urination, or whether it’s just because you’re taking on extra fluids. Of course, there is a high water content in coffee, which fills your bladder and gives you the urge to go.

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What does the research say?

A thorough study published in 2014 compared the results of coffee consumption with water consumption on 50 men in two separate trials and found no significant difference in the men’s total body water (TBW) at the end of each trial. This indicates that the men who drank the coffee didn’t lose any extra water as a result of the caffeine. Therefore coffee, when consumed in moderation, is as hydrating as plain water.1 It’s worth noting,however, that the participants in this study were already used to drinking between three and six cups of coffee daily, which might suggest they had developed a tolerance to the caffeine’s diuretic qualities.2

An earlier study on whether caffeine increases urination looked at doses of 45mg, 90mg, 180mg and 360mg of caffeine taken daily, and it was only at 360mg when urine output was increased.3This is the equivalent of three large cups of coffee.

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So, should you avoid coffee to maintain your fluid balance?

Unless you’re drinking more than three large cups per day, the answer is no. You can keep enjoying your coffee in moderation. However, if you are drinking three cups daily you might want to watch out for the stimulating properties of caffeine. Caffeine can stimulate the central nervous system and temporarily increase blood pressure and heart rate which can cause anxiety, heart palpitations and sleeplessness.4 Herbal teas or decaffeinated coffee would be a great choice if you’re prone to insomnia or stress.

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Advice is for information only and should not replace medical care. Please check with your GP before trying any remedies.

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  1.  http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0084154.
  2. https://www.nhs.uk/news/food-and-diet/a-small-amount-of-coffee-will-not-dehydrate-you/.
  3. https://www.ncbi.nlm.nih.gov/pubmed/3297472.
  4. https://www.ncbi.nlm.nih.gov/pubmed/10516914.

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