Green Coffee Extract: A Weight-Loss Aid?
Green coffee is simply coffee that has not been "cooked." Green coffee products are made from unroasted coffee beans, usually from the plant Coffea arabica.1 Most of the world enjoys coffee products that are manufactured from roasted coffee beans.
The most widely known natural component of coffee is caffeine but, in reality, coffee contains hundreds of bioactive chemicals, many of which are more significant than caffeine.1 Green coffee products have become widely popular as a potential weight-loss aid.
Green coffee extract contains chlorogenic acid, which is derived from a major group of phenolic compounds.2 Green coffee beans contain nearly twice the concentration of chlorogenic acid as do roasted beans. Chlorogenic acid is a major component of many OTC weight-loss products and acts independently of caffeine.2
The theorized mechanism of action by which green coffee produces weight loss is through the inhibition of the enzyme glucose-6-phosphatase.3 In vitro, glucose-6-phosphatase induces the enzymatic process of glucose production in the liver.3 It is this step in the metabolic pathway that researchers attribute to the known reduction of glycemic disorders in long-term coffee-drinkers.4
Green coffee extract is believed to aid weight loss. One trial evaluated the responses of 16 overweight adults who had been randomized to high-dose extract, low-dose extract, or placebo in a 22-week study.5 Body weight decreased by a mean of 8 lbs, with a mean drop in body fat of more than 4%.5
In another study, 50 volunteers with body mass indices >25 were randomized to placebo or to treatment with green coffee extract.6 After 60 days, members of the treatment group had lost an average of 5.7% of their body weight, with a shift in the muscle-mass-to-fat-mass ratio of +4.1%/-0.7% from baseline.6
In a trial designed to compare the effect of green coffee vs. roasted coffee on BP measurements, researchers randomized more than 200 subjects to either a placebo coffee drink or a drink with low, medium, or high chlorogenic-acid content.7
Each participant drank one cup of the treatment coffee per day and recorded BP readings for one month. At the end of the trial, not only were the BP readings of the placebo group higher than the BP readings of the treatment group, but a definite dose-response curve for the three treatment dose levels also was seen.
This indicates that the beneficial effect of coffee intake on BP has nothing to do with caffeine, but rather with the chlorogenic acid content. These findings have been validated by multiple studies examining different green coffee extract concentrations and populations.8, 9 In each trial, a statistically significant reduction of systolic BP was seen with no documented adverse effects.
Researchers looking at human vasoreactivity monitored nitric oxide activity in individuals after daily intake of a measured amount of green coffee extract. For four months, parameters indicative of endothelial function were monitored daily. At the end of the test period, the vasodilatory response was found to be significantly higher in the test group than in the placebo group, and total plasma homocysteine levels were also lower than at baseline.10
A small lab study using human cell culture lines focused on the chemoprotective and antigenotoxic activities of green coffee extract.11 Human colon and liver cells were treated with a dose-calculated solution of chlorogenic acid and cultured under the same conditions as the placebo cell cultures. Both cell lines were then tested for levels of oxidative stress, such as membrane disruption, DNA damage, and cell death.