Caffeine: Friend or Foe? (Part 2)

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How many of you are nursing a cup of coffee or tea or guzzling a can of diet cola as you read this? (I admit, I just polished off a glass of Diet Coke myself!) This week, we’ll take a closer look at how caffeine may affect diabetes.

Diabetes prevention
If you (or a loved one) are at high risk of getting diabetes, you may want to include a cup of joe in your daily routine. Several studies have shown that folks who drink coffee have a lower risk of getting Type 2 diabetes than those who don’t. One study, published in The Journal of the American Medical Association in 2004, looked at almost 15,000 Finnish people over 12 years. None of the people had diabetes at the start of the study. At the end of the study period, researchers discovered that those who drank at least 10 cups of coffee every day had the lowest risk of diabetes, compared to those who drank very little or no coffee.

Then, in 2006, a study published in Diabetes Care followed about 900 adults with prediabetes for eight years. Those who drank caffeinated coffee had a 60% lower risk of getting diabetes than those who didn’t drink coffee.

And another study published in 2006, also in Diabetes Care, looked at more than 88,000 women in the Nurses’ Health Study II. It found that women who drank two or more cups of coffee daily had a lower risk of getting diabetes than those who drank just one cup of coffee daily, or no coffee at all. And it didn’t matter whether the coffee was high-test or decaf.

So, while it looks like coffee may protect people from getting Type 2 diabetes, it’s probably not the caffeine in the coffee that does the trick, since decaf coffee seems to be protective, as well.

Coffee is more than just caffeine. Your morning java is a pretty good source of magnesium (a mineral that is also known for lowering diabetes risk by helping your insulin work more efficiently), potassium, vitamin B3 (niacin), and chlorogenic acid. Chlorogenic acid is a polyphenol (a type of antioxidant) that seems to enhance glucose metabolism by slowing glucose uptake in the digestive tract.

Diabetes management
Well, what if you already have diabetes? Can caffeine help make managing it a little easier?

Maybe not. According to a study published in February’s Diabetes Care, researchers at Duke University found that participants with Type 2 diabetes who were given 500 milligrams of caffeine a day (equivalent to 6–7 cups of coffee) in pill form experienced an 8% increase in blood glucose levels overall, and between 9% and 26% higher blood glucose levels after meals. Why this happened isn’t exactly clear—the study authors speculate that caffeine may interfere with the transport of glucose into cells, or that caffeine stimulates release of adrenaline (also known as epinephrine), a stress hormone that raises blood glucose. However, this study involved just 10 subjects—hardly enough to make any concrete conclusions. (To read more about this study, see “Caffeine May Affect Blood Glucose Levels.”)

Anecdotal evidence from people with Type 1 diabetes shows that caffeine doesn’t discriminate in terms of type of diabetes. For example, physicians and diabetes educators involved in Joslin Diabetes Center’s pump and glucose sensor programs have found that caffeine, whether in the form of coffee, tea, or diet cola, often raises blood glucose levels. Some of you have likely experienced this, as well.

It’s somewhat ironic, then, that coffee may protect you from getting diabetes, but once you have diabetes, it’s not exactly helpful. Caffeine does appear to have some other beneficial health effects, such as protecting against Parkinson disease and gallstones, along with increasing your alertness, improving your mood, and treating headaches. Yet, the downside is that it may increase the risk of infertility, miscarriage, and birth defects, and it can interfere with sleep and even trigger migraines. Caffeine—friend or foe? You decide!

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