If coffee is your favorite morning pick-me-up, read on.
The World Health Organization's cancer research agency has given coffee the green light. The group concludes that coffee does not pose a cancer risk, and experts say a regular coffee habit may even be protective of good health.
So, you'd never heard that there had been concern of a cancer risk from coffee? Yeah, that makes lots of us. In 1991, the World Health Organization's International Agency for Research on Cancer listed coffee as a possible carcinogen. This classification was based on what the IARC says was "limited evidence" that coffee was associated with a higher risk of bladder cancer.
But over the past 25 years, the body of evidence has pointed in a new direction. "Many epidemiological studies now available showed that coffee drinking had no carcinogenic effects for cancers," the IARC statement concludes.
Researchers reviewed more than 500 studies on more than 20 different types of cancers. The group concludes that coffee may in fact help protect against the risk of cancers of the liver and uterus. In addition, coffee consumption has been associated with a reduced risk of colorectal cancer in a number of studies.
As we've reported, a regular coffee habit has also been linked to longevity and a reduced risk of diabetes.
One word of caution: The agency warns that extremely hot beverages may increase the risk of cancer. For instance, the group looked at studies from South America where mate is consumed at very hot temperatures.
"Epidemiological studies found that cancer of the esophagus is associated with drinking mate at very hot temperatures but not with drinking mate warm or cold," the IARC concludes. The researchers also point to studies of tea in Asian countries, including China, that found the risk of esophageal cancer may increase with temperature.
The group concludes that the cancer-causing effects probably occur at drinking temperatures of 150 degrees Fahrenheit and above.
So, enjoy that cup of Joe — but not too hot.
ARI SHAPIRO, HOST:
This week, the World Health Organization turned its attention to everybody's favorite morning pick-me-up, coffee. The group's cancer research arm gave java a green light, concluding that coffee does not cause cancer. And, in fact, it might help protect against certain types of cancer. The announcement created a lot of buzz, especially the warning that came with it which boils down to this - don't drink your coffee or tea scalding hot. NPR's Allison Aubrey is here in the studio to explain.
ALLISON AUBREY, BYLINE: Hi there, Ari.
SHAPIRO: You brought a prop that we'll talk about in a moment.
AUBREY: I've got a nice cup of coffee here. It's...
SHAPIRO: What did this study find?
AUBREY: What the World Health Organization's cancer research arm is really concluding is that they've looked at over 500 studies now, and they say there is no evidence that a regular coffee habit - so drinking a cup or two of this every day - is linked to a higher risk of cancer.
And, in fact, there's gathering evidence that drinking a couple or two a day may actually decrease the risk of kidney and colorectal cancer. So I'd say, yes, the World Health Organization is giving us the green light. As long as we drink coffee in moderation, go ahead. Drink up.
SHAPIRO: Sort this out for me because 25 years ago, the World Health Organization said there might be a link between drinking coffee and cancer. How did they get this wrong? I feel like first it was wine then chocolate, now coffee that first we thought was bad for us now may be good for us.
AUBREY: Sure. They just didn't have the complete picture. So back in 1991 when they listed coffee as a possible carcinogen, they had very limited data. As I just mentioned, they've now reviewed 500 studies. And what they see is a much more complete picture. For many years, the habit of drinking coffee went hand-in-hand with cigarette smoking. So it was tough to disentangle the risk. What looked like a risk from drinking coffee was really from the smoking.
And the World Health Organization pointed this out this week. They say a lot of the early research, the research that pointed to perhaps a higher risk of bladder cancer linked to coffee drinking didn't account for this tobacco smoking. And, of course, now we know that tobacco smoking is a major risk for bladder cancer and coffee's not.
SHAPIRO: So I want to talk about one part of this study. In front of you, you have a cup of coffee with an enormous thermometer sticking out of it. Why is extremely hot coffee or tea something to worry about?
AUBREY: Sure. So the World Health Organization also looked at studies from South America and China and Japan, and they found that drinking very hot beverages - so in those countries tea and mate - was linked to an increased risk of cancer of the esophagus.
Now, the thought is that this extreme heat might play a role in producing tumors, at least that's what's been shown in animal experiments. And so the World Health Organization looked into this, and what they found is it's not the mate, it's not the tea. It's actually the temperature. They say...
SHAPIRO: How hot is too hot?
AUBREY: Right. They say that the risk starts at about 150 degrees. So what I did, I've just gotten a cup of coffee here from the coffeemaker down the hallway. It's too late in the day to be drinking caffeine, so this is decaf. When I first brewed it, it was coming out right at about 140.
Now it's down - way down because we've been sitting here a few minutes. So I have to say I'm not concerned. It seems that for most of us by the time we brewed it, put a little cream in it and get it to our lips, we're down under 150 degrees.
SHAPIRO: NPR's Allison Aubrey, thank you.
AUBREY: Thank you so much.
(SOUNDBITE OF SONG, "FORTY CUPS OF COFFEE")
ELLA MAE MORSE: (Singing) ...pulling out my hair. I drink 40 cups of coffee, 40 cups of coffee. Transcript provided by NPR, Copyright NPR.