When it comes to diabetes, is caffeine good or bad? The answer seems to be ... it's both.
By Joseph V. Amodio
Most of us are like Charlie Sheen. Or Lindsay Lohan. We could do with a little rehab.
Not because of criminal activity or illegal substances, but because of a perfectly legal — albeit addictive — substance consumed by millions worldwide. We're talking caffeine, that beloved ingredient in your morning coffee, afternoon Diet Coke or Mountain Dew, or late-night Red Bull that perks you up and helps you focus.
In terms of diabetes, however, caffeine can be perplexing. According to various scientific studies, coffee drinkers have a lower risk of developing type 2 diabetes — but for those with diabetes, caffeine raises blood sugar and increases insulin resistance.
Scientists admit the results are contradictory.
The Good, the Bad, and the Ugly Truth
First, the good news — a review of 18 studies with more than 450,000 participants found that each cup of coffee a person consumed was associated with a 7 percent lower risk of developing type 2 diabetes. In one study, those who drank seven or more cups per day were half as likely to develop diabetes as those who drank two or fewer cups per day.
But these were epidemiological studies — scientists ask about coffee intake, then watch to see who develops diabetes. It shows an interesting correlation, but doesn't establish cause and effect. It could be something else about the heavy coffee drinkers that protected them.
The bad news comes from several experimental studies, like one at Duke University in which 10 people diagnosed with type 2 diabetes ingested 500 milligrams of caffeine daily (250mg in gelatin capsule form — the equivalent of 1½ mugs of coffee — at breakfast and lunch) and had their glucose levels continuously monitored for several days. In this study, caffeine raised average daytime blood glucose levels by 7.5 percent and increased postprandial levels by 9 percent, 15 percent, and 21 percent following breakfast, lunch, and dinner, respectively.
Caffeine by the Numbers
This doesn't necessarily mean you should go cold turkey. First, consider your caffeine intake:
- NoDoz Maximum Strength (1 tablet) — 200mg
- Ground roasted coffee (10oz ceramic mug) — 170mg*
- Red Bull (8.3oz serving) — 67mg
- Excedrin Extra Strength (2 tablets) — 65mg
- Scharffen Berger Extra Dark 82% Cacao bar (1/2 bar) — 57mg
- Diet Mountain Dew (12oz can) — 50mg
- Ben & Jerry's Coffee Heath Bar Crunch ice cream (1/2 cup) — 42mg
- Tea (black, 8oz) — 40 to 50mg
- Diet Pepsi (12oz can) — 35mg
*Coffee's caffeine content varies, due to factors like coffee bean variety and brewing time. University of Florida researcher Bruce Goldberger, Ph.D., studied specialty coffees in 2003, purchasing a 16 ounce grande of Starbucks' Breakfast Blend at the same outlet on six consecutive days. Caffeine counts ranged from 259mg to 564mg of caffeine — nearly three times that of a NoDoz.
On the other hand, adding chocolate (which has small amounts of caffeine) to your beverage of choice doesn't affect the outcome much. Starbucks' 8-ounce Caff Latte (espresso in steamed milk) contains 75mg of caffeine; the Caff Mocha has just 10 mg more.
Until we know more, it's too soon to suggest those with diabetes avoid coffee entirely, according to Duke University researcher James D. Lane, Ph.D., in a 2011 review article in the Journal of Caffeine Research. Coffee's protective benefits might not come from caffeine at all, but another compound, he says. If you want to cut down, consider switching to decaf, but remember that doesn' mean "no caf," just less (about 6mg in a 10-ounce mug).
Or perhaps coffee drinkers have something else in common. A 2010 review found that consumers of sugar-sweetened beverages like sodas, fruit drinks, and energy drinks have an increased risk of type 2 diabetes. "Heavy coffee drinkers probably consume little or none of these other beverages," explains Lane. "The apparent benets of coffee drinking may simply be due to an avoidance of the sugar-sweetened alternatives."
Bottom line: Enjoy coffee and tea in moderation, and test after drinking so you stay aware of the effects on your blood sugar.
Reviewed by Susan Weiner, RD, MS, CDE, CDN. 5/12
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