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Green coffee bean extract is popular for its weight loss and blood pressure lowering properties. This article discusses the evidence behind these two health claims and whether green coffee bean extract is safe.
Green coffee bean extract – weight loss myth
The purpose of creating a green coffee extract was to produce a supplement containing a high level of and concentrated chlorogenic acid, which is believed to have various health properties including widely claimed weight loss properties.
The weight loss properties of these products usually come from the information on the products themselves, from scientific studies which are mostly biased (since they are sponsored by the industry) and from anecdotal evidence (which could also be initiated by the industry).
Green (raw) coffee beans are the best source of chlorogenic acid and the best way to obtain it is by extracting it.
Note: these products can contain caffeine, however decaffeinated types are also available.
There are other ways of obtaining chlorogenic acid but GCE supplements seem to be the best option. Brewing green beans produces an awful tasting beverage and roasting beans drastically reduces the amount of chlorogenic acid.
Studies on the effectiveness of chlorogenic acid in weight loss
A recent systematic review from 2011 (a study that combined all of the available studies and used statistics to calculate the overall results) concluded that all studies regarding the GCE might have been industry bias, and the methodology of these studies had poor quality.
More independent and high quality studies are needed to show if GCE or chlorogenic acid are effective in weight loss. (1)
One study, for instance, which showed significant weight loss in overweight people taking GCE has been retracted by the authors with the reason that “The sponsors of the study cannot assure the validity of the data”. (2)
Two studies from 2007, with no reported conflict of interest, showed that chlorogenic acid reduces weight when consumed as an addition to instant coffee. This effect is attributed to the decrease of glucose absorption.
The first study, using 12 participants, showed that when chlorogenic acid is mixed with instant coffee it shows a 6.9% reduction in glucose absorption compared to when instant coffee is taken on its own.
The second study, using 30 overweight participants, showed that overweight people who had chlorogenic acid added to coffee, lost 3 times more weight over a 3 month period than those that had only instant coffee. (3)
- There is insufficient evidence that green coffee extract (GCE), with its main active ingredient chlorogenic acid, has weight loss effects.
- The lack of strong evidence is because most studies were sponsored by companies producing GCE and, therefore, are biased.
- The long term effects of this supplement have not yet been thoroughly investigated. Therefore, caution is needed before starting to take GCE.
- More studies, with wider samples and independent from the industry, are needed.
Does green coffee bean extract reduce blood pressure?
In summary, studies clearly show the reduction in blood pressure following supplementation with green coffee extract, especially in people with mild hypertension.
Two studies clearly show the reduction in blood pressure following supplementation with green coffee extract.
The first 12 week study has shown that taking 140mg of chlorogenic acid daily from green coffee bean extract significantly reduced blood pressure in people with mild hypertension. This reasonably small amount of chlorogenic acid has not presented any side-effects. (6)
Another study found that, after 28 days, mildly hypertensive participants taking 93mg and 185mg doses of green coffee bean extract have shown a reduction in both systolic and diastolic blood pressure.
The drop in blood pressure was dose related – the higher the dose, the bigger reduction in blood pressure. (7)
TIP: If you consider taking green coffee bean extract for blood pressure reduction, take into account the recommended daily dosage to avoid possible toxicity and be aware that you might lose some nutrients if you take it with meals.
See other methods of blood pressure reduction here.
- Systolic and diastolic pressure is reduced significantly with the supplementation of green coffee extract.
Green coffee bean extract side effects and safety
There is a lack of sufficient evidence that green coffee extract is unsafe, toxic or unhealthy. However, a small number of people have presented some side effects after having green coffee extract.
The following explanation is based on studies on the green coffee extract effects sponsored by the supplement companies. Please bear in mind that the results presented may be biased.
There are no specific studies focusing on the daily dosages or safety levels of this product or chlorogenic acid itself. For this reason and the lack of sufficient reports on negative effects, the maximum dosage or recommended daily dosage has not yet been established.
It seems that the supplement companies set the available recommendations based on the chlorogenic acid amounts derived from the usual daily coffee intake.
Some studies conducted so far have identified cases of allergic reaction in green coffee factory workers due to the dust of the processed green coffee beans or contaminants from other products rather than the green coffee extract itself.
Other studies using the actual extract have recorded a small percentage of participants experiencing green coffee bean extract side effects from the commonly suggested (on the product labels) dosages.
Overall, there are very few reports on the negative side effects of the chlorogenic acid or green coffee extract and it is not entirely clear if these ill effects are due to other factors, chlorogenic acid or combinations.
It is important to note that green coffee extract is a reasonably new product, which in a short time became a new craze on the market and, as in most similar cases, its benefits may be way above the realm.
Yes, it may have a good set of benefits but we need to consider that it can cause some unwanted side effects in some people. The bottom line is that there is not enough evidence to support either conclusion.
Studies on green coffee extract and chlorogenic acid (main active ingredient of the supplement):
- Studies showing allergic reactions in workers in coffee factory (not directly linked to the supplement itself, but worth investigating further):
Some studies showed that allergens associated with green bean coffee are mainly found in the dust generated from processing coffee and primarily affects coffee factory workers.
These allergens are destroyed, nevertheless, by roasting the coffee beans. The other allergen found in green coffee beans comes from castor beans, through castor bean contaminated sacks which may be shared between the two products.
It was also found that green coffee extract inhalation may cause an allergic reaction (bronchoconstriction) in some people. (8)
A recent study from June 2012 discovered a new coffee allergen called (Cof a 1) that affected 3 out of 17 people working in the coffee processing factory. This allergen has not been linked to chlorogenic acid. However, it was extracted from green coffee extract. (9)
These studies found some evidence of the potential side effects from green coffee beans. However, it is unlikely that it is related to the supplement itself.
- Study on chlorogenic acid safety shows that it is safe in its purer form:
This study looked at the chlorogenic acid itself and discovered that high purity (92%) chlorogenic acid has not shown allergenic properties. (10)
- Study showing some side effects:
One small study (using 200mg of chlorogenic acid per day derived from 400mg of green coffee extract) (11) found some side effects such as headache and urinary tract infections in 2 out of 17 participants, placing some doubt on the safety of the extract. (12)
- Study showing no side effects (please note the smaller dose):
140 mg of chlorogenic acid from green coffee extract per day didn’t show side effects in participants with mild hypertension. (6)
NOTE: As described in the section below, absorption of minerals iron and zinc is reduced considerably when chlorogenic acid is taken within about an hour of the meal. It is best to take the supplement over one hour before or two hours after the meal for the maximum absorption of the minerals.
- There is lack of sufficient evidence showing that green coffee extract (or chlorogenic acid) is unsafe, toxic or unhealthy, even after long term intake or if taken in high dosages.
- Although there is no official upper limit, 200mg per day seems to be the amount used in the studies that haven’t recorded serious side effects.
- Pregnant women, children or people on medication should avoid it, due to possible untested side effects or contraindications.
Does chlorogenic acid deplete nutrients?
Many claims without references to the scientific studies have been made that chlorogenic acid is a “drug mugger” of magnesium, iron, zinc and vitamin B1. They recommend that green coffee extract consumption should be accompanied by supplements.
These claims are related to a recommendation that if green coffee extract is taken, it should be accompanied by trace mineral supplements containing all of these minerals. Since there are no strong scientific references to back-up those claims, here is a summary of the studies:
Phenolic compounds such as chlorogenic acid contained in coffee and black tea inhibit the absorption of iron. There is evidence that absorption of non-heme iron decreases with an increased concentration of coffee. (14)
When black tea is taken with a meal it reduces absorption of non-heme iron from that meal by 62% (35% by coffee). The reduction in absorption of iron is believed to be due to polyphenolic compounds such as chlorogenic acid. (15)
Another study showed that beverages containing 20-50mg of polyphenols such as chlorogenic acid reduce the absorption of non-heme iron by 50-70%. Beverages containing 100-400mg of polyphenols decreased absorption by 60-90%. Black tea showed the highest reduction in absorption of 79-94%. (16)
A cup of coffee taken with a hamburger reduced the absorption of iron by 39% and a cup of black tea by 64%. When the strength of coffee increased, the absorption fell even further. (17)
Chlorogenic acid was shown not to induce vitamin B1 deficiency, to what was believed before. (18)
- Green coffee extract contains chlorogenic acid which reduces the absorption of iron and possibly zinc.
- Green coffee extract supplement should not be taken with meals to guarantee the optimal absorption of these nutrients from food.
NUTRITION FACTS VS NUTRITION MYTHS
You will find a summary of the most common nutrition myths and evidence-based nutrition facts here.