By Jessica Cote, BS
Updated February 2013
Many of us are bombarded with spam advertising various weight loss products that we are happy to ignore, but when Dr. Oz showed his enthusiastic support for green coffee bean extract, it caught our attention. Since then, Dr. Oz has shown support for several other weight loss products, and green coffee beans are no longer flying off the shelves.
So what’s the verdict? The hype sounds too good to be true, and usually that means it isn’t true. This time, there’s some intriguing research to back it up, but if these pills really worked, wouldn’t the fad have lasted longer? Here’s what we know so far.
What are green coffee beans?
Green coffee beans are the raw, unroasted version of the roasted black coffee beans we use to make coffee. Because green coffee beans are bitter, they are usually consumed in the form of a supplement made from green coffee bean extract. The extract is made by simmering the raw beans in distilled water for 15 minutes. If bought in pill form, it should consist of 50% chlorogenic acid and does not need to contain caffeine.
Does green coffee bean extract really work for weight loss?
Human study #1: Effects on body weight, BMI, body fat, and heart rate
A study by Vinson, Burnham and Nagendran, published in a diabetes journal in 2012, tested 16 overweight but otherwise healthy adults over a period of 22 weeks. The men and women were randomized into three different treatments: high dose green coffee extract (1050mg), low dose extract (700mg), and a placebo (no active ingredient). After each six-week treatment, subjects went through a two-week “wash-out” period in which they stopped taking pills to cleanse their system. The order of these three testing conditions was random for each person and neither the subjects nor researchers knew which testing condition the subjects were assigned and when (that is referred to as a “double-blind study”). Dr. Nagendran tells us that the men and women were urged to consume no more than 1500 calories a day and had to report their diet in weekly journals. That should have resulted in weight loss for everyone, especially since the calorie intake was almost identical for all three groups during the 22 weeks of the study.[i]
What happened? Over the 22 weeks of the study (which included 10 weeks with either placebo or no pills at all), the men and women lost an average of about 17 lbs, which was more than 10% of their body weight on average. In addition, their percent body fat was reduced by an average of 16%. Heart rate and blood pressure either improved or stayed the same, indicating no serious health risks from the extract, and no other adverse reactions were reported. During the six weeks that they took placebo, they didn’t lose any weight. Perhaps most surprising, each of the 16 men and women lost weight during the 22-week period, which is extremely unusual in any weight loss study.
The study has three enormous shortcomings, however. The first is the very small number of patients (only 16) and the second was the short number of weeks (22). Dr. Nagendran tells us that in the weeks after the study was completed and the pills were no longer available, weight loss was generally maintained and some continued to lose some weight. However, those data were not presented in the article.
The study’s third weakness is that there are many companies selling green coffee bean extract in the U.S. and we don’t think any of them are the same company that made the pills for this study. Since neither the FDA nor any other agencies monitor the actual ingredients in dietary supplements, there is no way to know which (if any) green coffee bean products sold in the U.S. would work as well as those in the study.
There are a few other studies that also indicate the possible benefits of green coffee.
Human study #2: Effects on body weight
A peer-reviewed study published in 2007 tested 30 overweight people for 12 weeks.[ii]
They were randomly assigned to drink either regular caffeinated instant coffee or coffee enriched with chlorogenic acid. The researchers and subjects were not told which coffee each person was drinking.
Did anyone lose weight? The people who drank the enriched coffee lost an average of about 12 lbs, while those who drank normal instant coffee only lost an average of 4 lbs. Although the coffee enriched with chlorogenic acid might not have tasted exactly like regular coffee, it is unlikely that knowing whether or not they were taking the extract resulted in such a large difference in weight loss.
Human study #3: Effects on sugar absorption
In the same 2007 article, a second experiment tested 12 normal-weight healthy people. Each volunteer drank four types of beverages: regular caffeinated instant coffee, regular decaffeinated instant coffee, chlorogenic acid-enriched coffee, and water. Subjects drank one of the beverages with sugar and then researchers followed their sugar levels for two hours. The individuals waited one week between each testing phase and the order of beverages for each subject was randomly assigned. All researchers and subjects were blind to what they were taking, and their diets did not change during the study.[ii]
Results of this study showed that when people drank a coffee enriched with chlorogenic acid they absorbed 7% less glucose compared to when they drank the caffeinated and decaffeinated regular instant black coffee and water. Glucose, a type of sugar derived from the carbohydrates we eat, is absorbed by our intestines and the excess glucose not used to “fuel” our bodies is converted into fat. Reduced glucose absorption seems to lead to less fat production.
It works for mice
The studies of people were conducted after green coffee extract was shown to be effective with mice. A study published in 2006 showed that mice who ate green coffee bean extract gained less weight over two weeks than mice eating a regular diet. The green coffee bean extract also reduced the fat between their organs by 50% and slightly reduced levels of triglycerides (a type of fat) in the bloodstream.[iii] A similar study published in 2010 showed that mice who ate a special diet enriched with chlorogenic acid gained 16% less body weight and had 46% less fat mass after eight weeks compared to mice on a diet that was identical except it did not include chlorogenic acid.[iv]
Does it really work, and if so, why?
Before we draw any conclusions, we’d need larger human studies which last for more than a year. These preliminary results suggest that green coffee bean extract is safe and we know it’s relatively inexpensive. However, we really do not know if it works.
The black coffee beans used to make coffee have been roasted at 350-600°F. This extreme heat changes the chemical composition of the unroasted beans, greatly reducing the chlorogenic acid found in raw coffee beans. A study that tested seven different types of coffee beans from South America, Asia and Africa found that raw, green coffee beans contain anywhere from 34-43mg of chlorogenic acid per gram of beans, whereas the same beans roasted only contain between 2-9mg of chlorogenic acid per gram of beans.[v]
While experts are still not certain of all the roles chlorogenic acid plays in the human body, they believe that chlorogenic acid slows the release of glucose into the bloodstream, perhaps by inhibiting sugar absorption from starch consumption, thus decreasing caloric input and thereby reducing fat production.[i],[ii] Researchers also believe that chlorogenic acid increases the liver’s processing speed.[iv] This is important because the liver is in charge of breaking down insulin, a hormone that plays a major role in metabolizing carbohydrates and fats in the body.
Scientists designed an experiment to confirm that our bodies can digest and use chlorogenic acid. The results showed that humans can almost fully metabolize the acid. This finding confirms that chlorogenic acid might play a key role in altering metabolism.[vi]
In addition to raw coffee beans, chlorogenic acid is also found in sunflower seeds, apples, potatoes and eggplant. However, the levels are much higher in green coffee beans.
Could green coffee bean extract also provide other health benefits?
Whether or not green coffee bean extract can help you lose weight, could it have other health benefits? Studies in humans and animals have shown that using green coffee bean extract lowers blood pressure.[vii],[viii] A new study showed that chlorogenic acid might have the ability to target and kill some cancer cells. This cancer-fighting potential is most likely related to chlorogenic acid’s activity as an antioxidant, which can fight cellular damage.[ix] These results sound promising, but more research is still necessary to further investigate all potential health benefits.
Can green coffee beans harm you?
Individuals taking green coffee bean extract have not noticed any side effects during these clinical trials. However, there are some potential risks that have been identified. A study published in 2001 showed that chlorogenic acid, a major component of the raw beans, slightly raised concentrations of homocysteine in the blood.[x] Homocysteine is an amino acid that tends to be more prevalent in people with cardiovascular disease than in healthy people. Experts are still debating whether or not high levels of homocysteine cause cardiovascular disease, but even if they do there is no evidence that small increases in homocysteine would be harmful.[xi] A 2012 study demonstrated that chlorogenic acid might cause damage to DNA (the genetic “blueprints” of our bodies) in regular cells, but these results are very new and need further investigation.[ix]
Because the studies have only tested very small groups of people so far, it is difficult to know how safe or effective the extract would be if taken by thousands of people. The largest studies to date, which are also quite small, were financed by companies with interests in the sales of the extract. A study by Dr. Dellalibera and colleagues that was published in a French journal in 2006 tested 50 overweight volunteers for 60 days.[xii] The people who took green coffee extract lost 11 lbs on average while those who took placebo lost an average of 5 lbs. A second study tested 62 overweight volunteers for only four weeks.[xiii] People who drank a caffeinated coffee enriched with chlorogenic acid lost an average of 3 lbs while people who drank regular coffee only lost a quarter of a pound on average.
Green coffee bean extract is currently sold by different companies with varying directions and dosages. We think the best advice for anyone taking the extract is to follow the directions that were used in Human Study #1 (above). They found that a total daily dose of either 700 or 1050 mg of chlorogenic acid was safe and effective, taken 350 mg at a time either two or three times a day. Dr. Nagendran told us that the men and women took the pills two or three times a day, either before or during meals. Their patients were told to try to take the pills approximately six hours apart.
The bottom line
- Small studies of humans have shown that green coffee bean extract might help you lose weight and body fat.
- So far, people taking the extract in small studies have not experienced any serious side effects but it is important to do studies of the impact on heart disease. Diarrhea has been mentioned sporadically in online forums. As always, if you are on any medications or have any health problems, you should check with your doctor before taking any supplement. It might be helpful to bring a copy of this article, because many physicians are unfamiliar with the latest research on green coffee beans.
- Dietary supplements aren’t usually inspected by the FDA, which means that they may not contain the ingredients that are listed on the label. For the safest options, the only ingredient in the supplement should be Green Coffee Bean Extract (Chlorogenic Acid 50%).
- There are no studies examining long-term health effects.
[i] Vinson JA, Burnham BR, Nagendran MV. Randomized, double-blind, placebo-controlled, linear dose, crossover study to evaluate the efficacy and safety of a green coffee bean extract in overweight subjects. Diabetes Metab Syndr Obes 2012; 5:21-7.
[ii] Thom E. The Effect of Chlorogenic Acid Enriched Coffee on Glucose Absorption in Healthy Volunteers and Its Effects on Body Mass When Used Long-term in Overweight and Obese People. J Int Med Res 2007; 35(6): 900-908.
[iii] Shimoda H, Seki E, Aitani M. Inhibitory effect of green coffee bean extract on fat accumulation and body weight gain in mice. BMC Complement and Altern Med 2006; 6:9.
[iv] Cho AS, Jeon SM, Kim MJ, Yeo J, Seo KI, Choi MS, Lee MK. Chlorogenic acid exhibits anti-obesity property and improves lipid metabolism in high-fat diet-induced-obese mice. Food Chem Toxicol 2010; 48(3): 937-943.
[v] Moon JK, Yoo HS, Shibamoto T. Role of Roasting Conditions in the Level of Chlorogenic Acid Content in Coffee Beans: Correlation with Coffee Acidity. J Agric and Food Chem 2009; 57(12):5365-5369.
[vi] Farah A, Monteiro M, Donangelo CM, Lafay S. Chlorogenic Acids from Green Coffee Extract are Highly Bioavailable in Humans. J Nutr 2008; 138(12): 2309-2315.
[vii] Mubarak A, Bondonno CP, Liu AH, Considine MJ, Rich L, Mas E, Croft KD, Hodgson JM. Acute Effects of Chlorogenic Acid on Nitric Oxide Status, Endothelial Function, and Blood Pressure in Healthy Volunteers: A Randomized Trial. J Agric Food Chem 2012; 60(36):9130-9136.
[viii] Suzuki A, Kagawa D, Ochiai R, Tokimitsu I, Saito I. Green coffee bean extract and its metabolites have a hypotensive effect in spontaneously hypertensive rats. Hypertens Res 2002; 25(1):99-107.
[ix] Burgos-Moron E, Calderon-Montano JM, Orta ML, Pastor N, Perez-Guerrero C, Austin C, Mateos S, Lopez-Lazaro M. The Coffee Constituent Chlorogenic Acid Induces Cellular DNA Damage and Formation of Topoisomerase I- and II-DNA Complexes in Cells. J Agric Food Chem 2012; 60(30):7384-7391.
[x] Olthof MR, Hollman PC, Zock PL, Katan MB. Consumption of high doses of chlorogenic acid, present in coffee, or of black tea increases plasma total homocysteine concentrations in humans. Am J Clin Nutr 2001; 73(3): 532-538.
[xi] Wald DS, Morris JK, Wald NJ. Reconciling the Evidence on Serum Homocysteine and Ischaemic Heart Disease: A Meta-Analysis. PLoS One 2011; 6(2): e16473.
[xii] Dellalibera O, Lemaire B, Lafay S. Svetol, green coffee extract, induces weight loss and increases the lean to fat mass ratio in volunteers with overweight problem. Phytotherapie 2006; 4(4): 194-197.
[xiii] Ayton Global Research. Independent market study on the effect of coffee shape on weight loss- the effect of chlorogenic acid enriched coffee (Coffee Shape) on weight when used in overweight people. 2009.