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Mayo Clinic talks caffeine myths before National Coffee Day

Donald Hensrud, the director of the Mayo Clinic Healthy Living Program, answered some questions about coffee and caffeine before National Coffee Day on Oct. 1. The takeaway: go forth and imbibe, coffee-drinkers.

Dr. Donald Hensrud

Today is International Coffee Day. But what are some truths and myths about that steaming cup of java?

Donald Hensrud, director of the Mayo Clinic Healthy Living Program, had the answers to our questions.

I'm confused — is caffeine good or bad for us?

First of all, there's a difference between caffeine and coffee. One of the things people don't realize is that there are a lot of antioxidants in coffee. … There's fairly good data that coffee is protective against Type 2 diabetes. That effect is seen both in caffeinated and decaf coffee. So it's the other compounds in coffee that are responsible for the effect on diabetes.

Now on the flip side, there was an article (recently) in Mayo Clinic proceedings that showed that caffeine, separate from coffee, was related to lower overall mortality in a population study.


Why do we worry about drinking too much coffee, then?

Patients come in and say, 'I drink too much coffee.' And I say, 'Why?' And they say, 'Well, it's not good for you.' And I say, 'Why's that?' From a health standpoint, it's a no-brainer. The health effects are much more beneficial than any health risks. There's fairly good evidence that coffee is protective against Type 2 diabetes, Parkinson's disease, liver disease, and liver cancer. And possibly other conditions too that aren't quite as well worked out — alertness, processing speed, some suggestion about dementia, although it isn't entirely clear. And perhaps even some cancers as well.

The limiting factors are not health risks, such as increasing the risk of high blood pressure — which it doesn't — but side effects. And these are well-known: problems sleeping, heartburn, urinary symptoms, especially in people who are predisposed. Palpitations, heart racing and things like that. So if people are having side effects from it, they should cut back.

Is it possible to overdose on coffee?

Yes, it is, and again, it's not necessarily severe health risks, but severe side effects. Anxiety, nervousness, irritability. The other aspect of this is if caffeine is combined with alcohol (especially in energy drinks). And there are many case reports of adverse side effects, people having to go to the emergency department.

On that note, can coffee sober you up?

Haha. It will — independent of alcohol, it will increase alertness slightly. But it won't override the effects of alcohol.

Does coffee make people dehydrated?


Not as much as what people think. The body's pretty smart, and if it's dehydrated, if it needs fluid, it'll hang onto it, even if it comes from coffee or alcohol. Now, at large amounts, if might promote some dehydration, a little bit. Very large amounts.

Can it stunt children's growth?

I'm aware of no evidence of that, although I remember hearing that quite a bit when I was younger.

Does drinking black coffee help people lose weight?

Not anything clinically significant. People have looked at caffeine as an adjunct and it might have a very minor effect, but in general, not anything clinically significant.

Is there an ideal amount of coffee to consume every day?

You'll hear moderation, you'll hear one to two cups a day. But I'll go back to what I said earlier, that if somebody's not having side effects, that the data on diabetes show that there's a benefit, a dose-response relationship, up to six cups a day. The one caveat there is if someone's trying to get pregnant, at high amounts, it does interfere with conception and there's an increased risk of miscarriage.

Do you know any other coffee facts or fictions?


Another myth is with blood pressure. The data show that in people who don't consume coffee, if someone has a cup of coffee, it will raise blood pressure a little bit, for a while, a few hours or so. But tolerance develops to that. So if somebody consumes coffee regularly, there's no increased risk of high blood pressure or hypertension, and it doesn't seem to raise blood pressure in that setting. So the moral of the story is, if you are gonna drink it, probably best to consume it on a regular basis, to avoid that effect.

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