Just as black tea is made by processing green tea leaves from their original state, ordinary coffee is made by roasting green coffee beans. This processing alters the chemical makeup of the plant product. In an analogy to the medicinal study of green tea, an extract made from green coffee beans is undergoing increasing investigation as a possible health-promoting supplement.

Like green tea, green coffee bean extracts (GCBE) contains strong antioxidants in the polyphenol family. The primary polyphenol antioxidants in green coffee bean extract are in a family known as chlorogenic acids (CGA). Meaningful, if still preliminary, evidence hints that CGA may help reduce blood pressure. Other proposed uses of GCBE are based primarily on its caffeine content, as well as observational studies of ordinary coffee consumption and the possible health benefits of antioxidants in general.

Animal studies have found evidence that chlorogenic acids from green coffee bean extract can reduce blood pressure.1 Based on this, researchers have conducted human trials.

In a double-blind, placebo-controlled study of 117 males with mild hypertension, GCBE was given for one month at 46 mg, 93 mg, or 185 mg daily.2After 28 days, the results showed a significant improvement in blood pressure as compared to placebo in the 93 mg and 185 mg groups. The results seen were dose-related, meaning that the greater the dose, the greater the improvement. The finding of dose-relatedness tends to increase the likelihood that a studied treatment is actually effective. Antihypertensive benefits were also seen in a much smaller study using purified chlorogenic acids.3

GCBE has also shown a bit of promise for aiding weight loss4, perhaps in part due to its chlorogenic acid content.5 The caffeine in GCBE might also provide a slight weight loss benefit.

GCBE products are sometimes said to help prevent diabetes; however, this claim derives only from weak evidence involving consumption of ordinary coffee,6 and cannot be relied upon at all.

Roasted (as opposed to green) coffee beans contain the substances kahweol and cafestol, which appear to increase levels of LDL ("bad" cholesterol).7 The fact that GCBE does not contain these substances is used as an argument in its favor. However, these substances remain in the coffee grounds and so they are also not present in standard beverage coffee, so this is probably not a significant point. (Unfiltered or boiled coffee, with the grounds left in, however, may present a risk.)