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.2 After 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 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.)
In the large human trial of GCBE for hypertension noted above, the extract was most effective when taken at a dose of 185 mg daily.
Since green coffee bean extract typically contains about 30% chlorogenic acids, this works out to a dose of about 60 mg of chlorogenic acids daily. Another study used 140 mg of purified chlorogenic acids daily.
GCBE is thought to be a safe substance. In human trials, no significant adverse effects have been seen.
In theory, the caffeine content of GCBE could potentially cause problems for some people. However, since GCBE contains only about 10% caffeine by weight, a high daily dose contains no more than about 20% of the caffeine content of a strong cup of coffee.
Maximum safe doses in pregnant or nursing women, young children, or people with liver or kidney disease have not been established.
1. Kozuma K, Tsuchiya S, Kohori J et al. Antihypertensive effect of green coffee bean extract on mildly hypertensive subjects. Hypertens Res. 2006;28:711-8.
2. Watanabe T, Arai Y, Mitsui Y et al. The blood pressure-lowering effect and safety of chlorogenic Acid from green coffee bean extract in essential hypertension. Clin Exp Hypertens. 2006;28:439-49.
3. Suzuki A, Yamamoto N, Jokura H et al. Chlorogenic acid attenuates hypertension and improves endothelial function in spontaneously hypertensive rats. J Hypertens. 2006;24:1065-73.
4. Shimoda H, Seki E and Aitani M. Inhibitory effect of green coffee bean extract on fat accumulation and body weight gain in mice. BMC Complementary and Alternative Medicine 2006;6:9
5. Arion WJ, Canfield WK, Ramos FC, et al. Chlorogenic acid and hydroxynitrobenzaldehyde: new inhibitors of hepatic glucose 6-phosphatase. Arch Biochem Biophys. 1997;339:315–322.
6. Van Dam RM, Feskens EJ. Coffee consumption and risk of type 2 diabetes mellitus. Lancet. 2002;360:1477–1478.
7. Ranheim T, Halvorsen B. Coffee consumption and human health--beneficial or detrimental?--Mechanisms for effects of coffee consumption on different risk factors for cardiovascular disease and type 2 diabetes mellitus. Mol Nutr Food Res. 2005;49:274-84
Last reviewed December 2015 by EBSCO CAM Review Board Last Updated: 12/15/2015