Drinking more coffee may slightly reduce your risk of diabetes, and people who drink three or more cups daily appear to be at the lowest risk of all.
Researchers at Harvard University's School of Public Health analyzed data on more than 120,000 people's coffee consumption over several years. They found that those who increased their intake by more than a cup a day over a four-year period had a lower chance of developing diabetes in the following years.
Dr. Herbert Muncie, Professor of Family Medicine at LSU School of Medicine, says this large survey would seem to validate other, smaller studies done in the past.
"They had, actually, an 11 percent lower risk of type 2 diabetes in the subsequent four years for the people who consumed two cups a day," says Muncie.
And, those who had consistently higher coffee consumption, three or more cups a day, had a risk which was 37 per cent lower than those who consistently drank one or fewer cups a day, according to the Harvard research.
All in all, Muncie says it's good news for coffee drinkers, "especially since diabetes is such a significant problem for us in Louisiana."
The Harvard study is the latest to suggest a possible link between coffee and reduced diabetes risk. And, while the researchers said that bigger, clinical trials would be required to confirm their findings, they believe that existing evidence of coffee's benefit is "well established".
"I think there's more likely to be a benefit, and certainly no harm," says Muncie. "It's not a reason to drink coffee, but certainly a good reason to be reassured that it's okay to drink the two, three or four cups a day that we want to consume."
While researchers say exercise and maintaining a healthy diet were by far the best ways to cut the risk of type 2 diabetes, there were also "biologically plausible" theories as to why coffee might also help.
Coffee has a lot of bio-active compounds, including chlorogenic acid, which improves glucose metabolism when tested in animals. Coffee is also a rich source of magnesium, which is known to be associated with a lower risk of type 2 diabetes.
As for drinking too much coffee, Dr. Muncie says most folks will self-regulate. Once they get beyond a certain amount, they'll start feeling the side effects.
"There's really not any evidence that caffeine or coffee is harmful, from a medical perspective, for almost any of us...and certainly in terms of adults."
What about putting sugar in your coffee? Dr. Muncie says it's really a matter of calories.
"If you have too many calories and gain weight, that's definitely associated with an increased risk of diabetes. And so, if the way you get too many calories is with sugar, that's probably not as good a thing to do."
Is there a difference between sugar and artificial sweeteners?
"There's a difference, mainly, in calories. And so, I don't think the sugar substitutes are at all risky or harmful. So, if people want to reduce their calories and have something sweet...that's how I take my coffee...I put in a sugar substitute for that."
Some experts in the UK said that it was still not clear that coffee was directly responsible for the lower diabetes risk scores shown in the Harvard study.
"There's certainly never a reason for people to absolutely drink caffeine or coffee," says Muncie. "But it's, at least, a good piece of information in terms of reassuring them."