By Johannah Sakimura
Green coffee bean supplements, the latest weight loss craze to lure dieters, may also improve blood sugar levels, according to new research. The latest findings could send people with type 2 diabetes flocking to the drugstore to pick up a bottle, but experts say you're better off waiting to see if the science catches up to the hype.
The supplements contain extracts from green coffee -- coffee beans in their raw, unroasted state. Green coffee contains hundreds of plant compounds, including chlorogenic acids, the antioxidants that are thought to be most responsible for the fresh beans' unique health perks. Unfortunately, regular brewed coffee made from roasted beans doesn't deliver the same potent dose of chlorogenic acids because the roasting process destroys most of the compounds.
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Green coffee started generating buzz last year when a small study found that the supplements could help people shed weight. Sixteen overweight individuals who took two different doses of green coffee extract over the course of a 22-week study lost a total of 17 pounds and 4 percent of their body fat.
Shortly after, the beans got a big boost from Mehmet Oz, MD, America's favorite television doctor. When Dr. Oz promoted green coffee as one of the top five "fastest fat burners" on his popular daytime show, demand for the pills exploded, said Joe Vinson, PhD, the lead author of the weight loss study and a chemist at the University of Scranton.
Green Coffee for Better Blood Sugar Control?
Now, Dr. Vinson and his colleagues have completed a second study on green coffee extract, this time showing that the supplement may have beneficial effects on blood sugar levels.
In the latest trial, 56 men and women with normal blood sugar levels drank a solution containing a standardized amount of pure glucose -- or sugar -- and had their blood sugar measured at regular intervals for the following two hours. The participants then repeated the glucose test multiple times using different doses of green coffee extract.
At all doses, green coffee extract caused a significant reduction in blood sugar compared to levels during the baseline test, but the highest dose -- 400 milligrams -- had the greatest effect. When individuals consumed the maximum amount tested, their peak blood sugar 30 minutes later was 24 percent lower on average than when they didn't take the supplement.
The results were presented today at the annual meeting of the American Chemical Society in New Orleans. The study, like Vinson's earlier weight loss trial, was conducted in India and funded by Applied Food Sciences, Inc., a company that manufactures green coffee extract.
High blood sugar is a concern for people with type 2 diabetes. A supplement that aids weight loss and improves blood sugar control simultaneously could be very valuable, according to Vinson, since obesity and diabetes often occur together. "If you had something that dealt with both problems, that's a very good thing," Vinson said.
However, it's unclear whether the supplements have the same blood sugar-lowering benefits for people with type 2 diabetes. "The people in this study were not diabetic -- they had healthy blood sugars," said James Lane, PhD, a psychophysiologist at Duke University who studies caffeine metabolism. "There's no evidence that these results would apply to people who are diabetic."
Also, the new study looked only at the immediate changes in blood sugar levels. Vinson hopes other researchers will conduct long-term studies to see if the favorable effects persist when people take the supplements for several weeks or months.
Scientists haven't yet determined how chlorogenic acids might act to reduce blood sugar. Laboratory studies have shown that the compounds may interfere with the breakdown of starch into glucose, possibly reducing sugar absorption into the blood, but experts said the mechanisms are still largely theoretical.
"Chlorogenic acids have been talked about for about 15 years now," said Terry Graham, PhD, a physiologist at the University of Guelph in Canada who has studied coffee extensively. "They're definitely very exciting compounds, but their immediate effects are still not well known."
If chlorogenic acids do in fact block carbohydrate absorption, that may not necessarily be a healthy outcome, said Dr. Graham. Supplements that meddle with digestion can cause malnutrition, diarrhea, and other health problems.
However, the participants who used the supplements in the 22-week weight loss study did not report any side effects, noted Vinson.
Graham said there just isn't enough information for him to recommend green coffee supplements at this time. "The data are very interesting, and it's worth following up, but it would take a lot more information before I think it would be worth swallowing the supplement," said Graham.
The Diabetes-Coffee Conundrum
Unlike a cup of coffee, green coffee supplements are typically low in caffeine, which may also help to explain their blood sugar-lowering potential.
Caffeine negatively affects blood sugar in both healthy people and those with type 2 diabetes, at least in the short term, according to studies. "There's a solid body of evidence showing that caffeine impairs glucose control and raises blood sugar after a meal," said Dr. Lane.
However, the relationship between coffee and diabetes is a complicated one. Despite caffeine's ability to increase blood sugar, long-term population studies consistently show that coffee drinkers are at lower risk for type 2 diabetes than non-drinkers. A Harvard University review of nine studies that followed nearly 200,000 participants found that people who drank four to six cups of coffee per day were 28 percent less likely to develop diabetes than those who drank two or fewer cups.
It's difficult to unravel the complex interaction between coffee, caffeine, and diabetes, since many of the studies on coffee consumption and diabetes don't distinguish between caffeinated and decaffeinated drinkers. Nevertheless, it appears that the health-boosting properties of chlorogenic acids - and the hundreds of other substances found in a single cup of joe - may offset the negative impact of caffeine.
The bottom line, according to Graham: "Coffee is healthy in terms of diabetes -- caffeine is not."
All of the experts agreed that people with type 2 diabetes and those at high risk are better off drinking decaf coffee if they're looking to improve blood sugar control.
Weight-Loss Benefits of Green Coffee Still Uncertain
As for evidence of green coffee's fat-burning benefits, scientific support is limited. While a handful of studies have shown that the supplement boosts weight loss, most are of poor quality and involved only a small number of participants.
"I would be very hesitant to endorse it as pro-weight loss," said Graham. "It might work but I don't think there's strong evidence one way or another."
Further, many of the green coffee supplements sold today may be little more than pricey placebos. After Dr. Oz touted green coffee supplements as a "miracle" fat burner to millions of viewers, Vinson said companies flooded the market with imitation products that contain little or no chlorogenic acid. A recent analysis by ConsumerLab.com, a company that evaluates nutrition supplements, found that half of the eight brands tested didn't deliver the amount of chlorogenic acid stated on the label.
In regard to both weight loss and blood sugar regulation, scientists still don't have a good understanding of what the supplement is doing, how it does it, or what its long-term effects might be, according to Graham. "On that," he said, "it's buyer beware."
"Green Coffee Supplements: Science Doesn't Support the Buzz" originally appeared on Everyday Health.