Preliminary findings from several animal experiments and some human studies have shown that both green coffee extract and its major phenolic compound chlorogenic acid have shown thermogenic fat-burning effects, as well as other health promoting actions. For example, a green coffee extract prevented weight gain and fat accumulation in mice. Green coffee extract has been shown to contain significant amounts of chlorogenic acid, and other polyphenolic compounds with anti-oxidant activities. Animal studies have reported that chlorogenic acids appear to target fat stores in the liver. One of the key questions is whether these bioactive nutrients are bioavailable when humans ingest green coffee extract. French researchers studied the pharmacokinetic profile after ingestion of green coffee extract in healthy men and women. Subjects consumed 2 capsules (400 mg) of decaffeinated green coffee extract containing 170 mg of chlorogenic acids. Blood samples were measured sequentially for 8 hours and urine samples collected to estimate bioavailabilty of various compounds in green coffee extract. The total bioavailability varied from person to person from as little as 7.8% to as high as 72% with an average of 33%. Several different chlorogenic acids were detected in blood after ingestion including caffeoylquinic, ferulic, caffeic, and isoferulic acids. The significant increase in ferulic acid is interesting because it has been shown to stimulate nitric oxide bioavailability and have a positive effect on vascular dilation and blood pressure. The authors conclude that the major compounds in green coffee extract are highly absorbed and metabolized in humans.

Farah A, Monteiro M, Donangelo CM, Lafay S. Chlorogenic Acids from Green Coffee Extract are Highly Bioavailable in Humans. J Nutr. 2008 Dec;138(12):2309-2315.