The Case for Unsweet Tea

Thoughts on diving and hydration

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Steve Lewis is a British diver, instructor, dive industry consultant and author based in Canada.

He teaches and lectures at home and abroad.

His main focus is to dive safety and to make each of us aware of the things that will make us better divers than we are now.

His latest book, Staying Alive: Risk Management Techniques for Advanced Scuba Diving, is available through Amazon.

For more information, visit or

I am an expat Brit, so it may probably come as no surprise to tell you that I enjoy a cup of tea. A few shots of strong espresso in a bowl of hot milk is my morning drink, but tea is on the menu for most of the rest of the day.

Perhaps less easy to fit into the ethnic stereotyping is the way I prefer my tea made. My strong preference is not the traditional British Cuppa (pipping hot with milk and sugar) but ice-cold, black with lemon, and unsweetened—a version of tea drunk in the southern part of the United States and often difficult to find most any place else, especially where I live in rural Canada.

Unsweetened tea is a great drink anytime but it’s a particularly good way to punctuate scuba dives. I guess it’s common knowledge among the dive crowd that “being well hydrated” is a good tactic that helps one’s body off-gas during ascents and surface intervals. We believe, in short, that hydration is a factor in decompression stress management; and although we might debate that this is a sweeping generalization, let’s just say that drinking lots of fluid is good behavior for any diver. In my opinion, drinking unsweet tea as well as plain water encourages higher consumption. In other words, tea is less boring than water.

Now just in case you are reading this and saying quietly to yourself: “Guy’s an idiot. Tea is a serious diuretic and divers should steer away from it,” give me a couple more minutes.

And by the way, if you ARE thinking that, you’re not alone. I was recently on a dive boat (an excellent liveaboard working out of the Florida Keys). Always open for suggestions and customer feedback, one of the owners asked what I would change about their operations. I suggested their soda gun have a button for unsweetened tea added. She looked at me with a smile and explained that tea being “the most powerful diuretic known” I would not be seeing it on the menu for her divers anytime soon. I resisted the temptation to argue with her.

For example, I resisted the temptation to point out the boat’s soda offerings included cola and root beer, both of which have serious dietary side effects from ingredients not to be found in tea. I also chose to not point out that there was a huge canteen of coffee on the galley counter below decks… surely if tea is diuretic, that must be too. Right?

Facts about tea

Tea is, at worst, mildly diuretic—with the emphasis on mildly. While you may poo-poo the veracity and question the bias of any study I care to cite here, data—and not some hearsay from a dubiously researched diving manual—indicates that everyday consumption of tea (hot or otherwise) does not produce a negative diuretic effect unless the amount of tea consumed at one sitting contains more than 300mg of caffeine. Since the average cuppa contains around 50mg, you’d have to drink about 1.5 litres of tea in one sitting to ingest this level of caffeine. That, my friends, would take some serious guzzling.

It may be worth noting that the British Dietetic Association (BDA) has suggested tea can be used to supplement normal water consumption! Nothing there about tea being counter-indicated for good hydration… the opposite, in fact. The BDA report went on to state that “the style of tea and coffee and the amounts we drink in the United Kingdom are unlikely to have a negative effect [on hydration]”. I think we are safe to apply the same logic anywhere else in the world.

A clinical study published by the British Tea Advisory Panel (admittedly a potentially biased source) stated that a cup of tea can be just as good as a glass of water at keeping your body hydrated. It explained that four to eight cups of tea consumed throughout the day, is thirst quenching “without any diuretic side effects”. Now, I am willing to squint a little at one or two of those assumptions without adding some provisos but it’s interesting nevertheless.

In addition, the Harvard School of Public Health rates tea as one of the healthiest beverages. Tea contains essential nutrients that are being studied for their value in possibly preventing heart disease and diabetes. For instance, brewed tea is rich in free-radical fighting antioxidants.

Unsweetened ice tea is also naturally low in calories. A 16-ounce glass of unsweetened ice tea (that’s a little less than half a litre) will deliver about three calories. The same volume of cola contains about 180 calories, all of which come from sugar.

Now you are free to drink whatever you want. And if I am on your boat, I will follow your rules and allow you to live by whatever odd dietary foibles you may have. But, please get something straight, unsweetened iced tea is NOT a serious diuretic and, in fact, may encourage divers who have an issue drinking a healthy dose of water to actually better hydrate.

Good hydration—or at least being conscious of it—is a lifestyle choice that one should adopt outside diving. Being well hydrated begins long before walking onto a dive boat or driving to the dive site... days before. But for a great number of people, drinking copious volumes of water simply doesn’t appeal. They want flavor. My argument is that unsweetened ice tea delivers it, and at the same time, helps, not hinders, one to attain and maintain a good level of hydration.

Of course, when we consider the overall factors that influence decompression stress, hydration is only one of more than perhaps a couple of dozen. But it is a simple one to manage... Anyone for a cuppa? â–