Coffee and Tea Are Not Dehydrating?

coffee and tea

Story at-a-glance -

  • A notion many have accepted as a matter of course for years — that drinking coffee or tea essentially saps your body of moisture through the dehydration process — is false information, a new study reveals
  • Drinking the right amount of coffee per day may lower your risk of developing atherosclerosis, and previous reports note other benefits, from lowered cognitive decline to helping ringing in the ears (tinnitus)
  • A recent study shows that coffee consumption may have a potential beneficial effect for fighting cardiovascular disease (CVD) as well as coronary calcification, particularly in nonsmokers
  • Consumption of sugar-sweetened soda is associated with a higher risk of kidney stone formation, while drinking tea and coffee — both caffeinated and decaffeinated — lower the risk

By Dr. Mercola

When you're really thirsty, a refreshing glass of water is the healthiest thing to drink, but in those moments, you probably don't crave coffee or tea. However, in spite of the fact that the caffeine in those beverages will have a diuretic effect, those comforting pick-me-ups are not dehydrating, as many people believe. So essentially, the notion many have accepted as a matter of course for years is false information.

While drinking coffee and tea tends to generate an urge to empty your bladder and simultaneously flush waste from your kidneys, it does not dehydrate you. The good news about drinking coffee and tea is that when you urinate, you won't lose more than you take in when you drink a caffeinated beverage.

One reason people feel that coffee and tea must be dehydrating, aside from this myth being standard nutritional dogma for some time, is that caffeine does tend to trigger frequent urination, which only stands to reason would pull moisture out of your body, right?

But quotes Daniel Vigil, associate clinical professor of family medicine at the David Geffen School of Medicine at the University of California Los Angeles, who contends that when you drink a cup of coffee or a glass of iced tea, you're also taking in fluid along with the caffeine. In fact:

"Even though caffeine is a mild diuretic, Vigil says, you won't lose more fluid through urine than you take in by drinking a caffeinated beverage. Your body is able to absorb as much fluid as it needs and expel the rest … For that reason, your morning pick-me-up actually helps hydrate you, not the opposite. Vigil says that coffee and tea 'can and should' count toward your daily eight-or-so cups of water per day."1

As an aside, the fact that you may develop a headache or other not-so-pleasant symptoms when deprived of your go-to mug of energy probably isn't about dehydration but instead may be more about caffeine deprivation, especially if you've been drinking it for a long time and suddenly find yourself deprived for a day or more.

If you're an avid coffee drinker, it may come as no surprise that more than half the population — 64 percent, according to the National Coffee Association (NCUSA)2 — declare themselves to be coffee imbibers, but that rate is climbing. Fully 70 percent of the coffee consumed is considered gourmet, the site says, and the rest is just "regular." Some may not be aware that, as the Journal of the American Heart Association reported, coffee may help protect your heart.

Coffee Has Its Merits, Including Those for Your Heart

A number of clinical findings reveal that coffee has a number of rather surprising merits, from boosting your energy to enhancing your mood. Medical News Today3 recently divulged another highly interesting discovery: Drinking more than three cups of coffee a day may lower your risk of developing atherosclerosis, also known as clogged arteries, a condition that seriously increases your heart disease risk, by 63 percent.

The study, called ELSA‐Brasil (Brazilian Longitudinal Study of Adult Health), used only participants from São Paulo, and noted that "habitual consumption" of coffee was beneficial but only among "never smokers." More specifically:

"The current study found that habitual coffee consumption was inversely associated with coronary calcification, a marker of subclinical coronary atherosclerosis … Our findings suggest that coffee consumption could exert a potential beneficial effect against coronary calcification and CVD risk, particularly in nonsmokers."4

But there are more potential benefits for your heart from drinking coffee. A Ph.D. student and two researchers at the University of Colorado School of Medicine in Aurora had the results of their work presented at the 2017 American Heart Association's (AHA) Scientific Sessions in Anaheim, California. According to Medical News Today, the study authors:

" … [U]sed machine learning alongside traditional data analysis techniques to uncover an inverse relationship between how much coffee we drink per week and how exposed we are to heart failure and stroke … In the first instance, the researchers employed the random forests algorithm in machine learning to examine data sourced from the Framingham Heart Study, which has been running since 1948."5

Machine learning, by the way, also referred to as "big data analytics" is used to accumulate, manage, analyze and assimilate large volumes of different types of data, and it's proven effective in health care. It can actually predict outcomes based on associations and identifying patterns in large amounts of information.

Interestingly, the researchers using the machine learning data discovered that an extra cup of coffee every week is associated with even better odds for your heart: a 7 percent decreased risk of heart failure and an 8 percent decreased stroke risk.6 Further, traditional data analysis revealed — and therefore confirmed, the researchers emphasized — the same link between coffee drinking and a reduction in stroke and heart failure risks.

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Coffee and Tea Impart Mental, Physical and Emotional Benefits

Another study showed that the risk for developing kidney stones is raised with the consumption of some beverages, such as sugar-sweetened cola (which elevated the risk by 26 percent), while caffeinated coffee lowered the risk by 26 percent, decaffeinated coffee lowered it by 16 percent, and tea lowered the risk 11 percent.7

You'll find lots of evidence for the advantages you get from having three, four and even five cups of coffee. In fact, indulging in your coffee passion is clinically linked to longer life; another way of saying it is that you have a lower risk of dying earlier than you should (premature death) or, likely, from heart disease or some other cardiovascular issue. Further, at least one study8 shows it can lower your risk of developing:

Nonalcoholic fatty liver disease


Glioma brain tumor9

Cognitive decline and cognitive impairment


Cancer, numerous types10

Tinnitus in women (ringing in the ears)11

Alzheimer's disease and other forms of dementia

As for tea, the second-most-consumed beverage in the world after water, the health benefits from green matcha tea, especially, are also dramatic, serving up such advantages as lowered inflammation, lowered blood pressure and less oxidative stress. In addition, it's associated with a reduced risk of death of any cause, which may have something to do with improvements in such areas as:

Weight loss

Heart health

Stronger bones

Type 2 diabetes

Protected vision


However, there is a caveat: While many prefer their coffee and tea to be plain and their coffee black, sans cream, sugar or the plethora of unhealthy additives like fake creamers and fake sweeteners, there are just as many who want them, even if they know they're not a wise health choice and usually are not even real. In other words, the benefits discussed above are for plain coffee and tea only.

But for (nearly) every rule, there are exceptions, such as the coffee addition that actually enhances the advantages. Adding coconut oil or medium-chain triglyceride (MCT) oil (the "ultimate ketogenic fat") may help you not only burn fat faster but improve your mitochondrial function. And to address the main point — that coffee and tea aren't dehydrating after all — remember, the best way to hydrate your body is by drinking plain, pure water (and not the many sports drinks currently on the market).

There's a simple mechanism for hydrating the right amount for your body: let thirst be your guide. Last but not least, when drinking coffee, certified organic and shade grown is by far the healthiest option, because coffee beans are one of the most heavily pesticide-sprayed crops. It's equally important to choose organic tea, when available, as well as choose varieties grown in nonpolluted areas, as tea plants readily absorb lead and fluoride from the soil.