Green Coffee seeds (Coffea Canephora Robusta) are raw, unroasted coffee seeds. Roasting process appears to destroy or at least to some extent reduce the content of some of the chemicals in the coffee beans, particularly chlorogenic acid (ester of caffeic acid and quinic acid) which is the main constituent of green coffee extract. Green coffee extract is marketed as a weight loss supplement under a variety of brand names such as “Coffee Slender”, and “Svetol” .
Green coffee vs. roasted coffee
A study by Dagalia and others  evaluated in vitro antioxidant activity of green coffee compared to roasted coffee. Green coffee samples had a slightly higher antioxidant activity compared to roasted coffee. The Ochratoxin A (food-contaminating mycotoxin) content was evaluated by many studies in both roasted and green coffee [2-3]. Cleaning of green coffee beans reduces Ochratoxin A to some extent but the most significant reduction happens during roasting . So the roasted powder contains only 13% of the Ochratoxin A initially present in the green beans . Another study showed that roasting eliminates Ochratoxin A contamination from 48% to 100% . Roasting process also destroys green coffee extract constituent – chlorogenic acid . Chlorogenic acid is a plant compound that may have some effect on keeping down glucose absorption .
Can green coffee extract really aid in weight loss?
There is some evidence from animal studies regarding the use of green coffee extract as a weight loss supplement [7,8]. The purpose of a review article published in 2010  was to assess the efficacy of green coffee extract as a weight loss supplement by only using data from human clinical trials. The analysis of three clinical trials that met their inclusion criteria revealed a significant difference in change in body weight between green coffee extract and placebo. However, the trials were not homogeneous compared to each other. Furthermore, the significance was moderate and clinical relevance is therefore not certain.
A small study , funded by Applied Food Sciences (maker of green coffee antioxidant supplements), yielded impressive results. 16 overweight subjects received 700 mg or 1,050 mg dose of the ground coffee beans or a placebo. Body weight declined by an average of 10.5%. The study participants lost slightly more weight with the higher dose compared to the lower dose, but not a significant amount with the placebo.
Are there any side effects?
None of the trials evaluated in the review article mentioned above reported any adverse events associated with the use of green coffee extract . However, green coffee seems to cause few side effects, like roasted coffee, due to caffeine content . Symptoms may include headache, upset stomach, anxiety .
- Daglia, Maria, et al. “In vitro antioxidant and ex vivo protective activities of green and roasted coffee.” Journal of Agricultural and Food Chemistry 48.5 (2000): 1449-1454.
- Studer-Rohr, Irène, et al. “The occurrence of ochratoxin A in coffee.” Food and chemical toxicology 33.5 (1995): 341-355.
- Romani, Santina, et al. “Screening on the occurrence of ochratoxin A in green coffee beans of different origins and types.” Journal of Agricultural and Food Chemistry 48.8 (2000): 3616-3619.
- Blanc, Maurice, et al. “Behavior of ochratoxin A during green coffee roasting and soluble coffee manufacture.” Journal of agricultural and food chemistry 46.2 (1998): 673-675.
- Micco, C., et al. “A study of the contamination by ochratoxin A of green and roasted coffee beans.” (1989): 333-339.
- Onakpoya, Igho, Rohini Terry, and Edzard Ernst. “The use of green coffee extract as a weight loss supplement: a systematic review and meta-analysis of randomised clinical trials.” Gastroenterology research and practice 2011 (2010).
- Shimoda, Hiroshi, Emi Seki, and Michio Aitani. “Inhibitory effect of green coffee bean extract on fat accumulation and body weight gain in mice.” BMC Complementary and Alternative Medicine 6.1 (2006): 9.
- Cho, Ae-Sim, et al. “Chlorogenic acid exhibits anti-obesity property and improves lipid metabolism in high-fat diet-induced-obese mice.” Food and Chemical Toxicology 48.3 (2010): 937-943.
- Kathleen Doheny. “Green Coffee Beans May Aid Weight Loss” Retrieved from WebMD.com at 7. May 2013