What research says about green coffee’s ability to support metabolic health
Coffee enjoys the limelight as a compound with profound potential to support healthy aging. Within the plethora of coffee research in recent years, green coffee beans have also gained recognition over the last two decades as a wellness supplement rich in health benefits.
As a source of an important class of polyphenols known collectively as chlorogenic acids, unroasted (or green) coffee beans have been studied for their effects on blood sugar, blood pressure, and cardiovascular health. In fact, research shows that chlorogenic acids exhibit antioxidant, anti-inflammatory, and neurological benefits while also exerting significant effects on glucose and lipid metabolism.(1) As such, chlorogenic acids may influence a broad range of health conditions.
Despite being the subject of controversy-most notably a 2014 FTC investigation surrounding green coffee and deceptive advertising claims(2)-the science supporting green coffee continues to shine in areas including vascular health, insulin metabolism, liver function, and body composition. Several exciting new studies are highlighted ahead.
1. Tajik N et al., “The potential effects of chlorogenic acid, the main phenolic components in coffee, on health: a comprehensive review of the literature,” European Journal of Nutrition. Published online April 8, 2017.
2. “FTC Charges Green Coffee Bean Sellers with Deceiving Consumers through Fake News Sites and Bogus Weight Loss Claims | Federal Trade Commission.” (2014). www.ftc.gov/news-events/press-releases/2014/05/ftc-charges-green-coffee-bean-sellers-deceiving-consumers-through. Accessed May 23, 2017.
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Improved Vascular Health
Various polyphenols have been shown to support vascular health. In a recently published paper, European researchers led by Charlotte Mills of the University of Reading (Reading, UK) investigated the ability of chlorogenic acid and its metabolites from green (unroasted) coffee beans to influence endothelial health.(3)
The researchers conducted two randomized, controlled, crossover studies looking at the acute effects of supplementation with coffee containing 89 mg or 310 mg of chlorogenic acids, as well as the chlorogenic acid metabolite 5-caffeoylquinic acid (5-CQA) administered in amounts of 450 mg or 900 mg, in a single dose. Both studies included healthy male participants and investigated flow-mediated dilation (FMD), a measure of endothelial health.
In the first study, the investigators observed a biphasic response to coffee administration with low and high chlorogenic acid content, with increases in FMD seen at 1 and 5 hours after consumption. These increases correlated with the appearance of chlorogenic acid metabolites in the blood.
In the second study involving direct administration of the metabolite 5-CQA, the researchers also noted an improvement in FMD versus control, supporting the vascular health benefits of chlorogenic acid and its metabolites.
3. Mills CE et al., “Mediation of coffee-induced improvements in human vascular function by chlorogenic acids and its metabolites: two randomized, controlled, crossover intervention trials,” Clinical Nutrition. Published online November 30, 2016.
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Healthy Glucose and Insulin Metabolism
Research indicates that chronic coffee consumption may enhance long-term glucose metabolism. Scientists believe this a function of chlorogenic acid and its metabolites. A new study aimed to explore this relationship in healthy men and women.
As green (unroasted) coffee is richer in antioxidant polyphenols such as chlorogenic acids than roasted coffee, Beatriz SarriÃ¡ and colleagues from the Spanish National Research Council (Madrid, Spain) evaluated the effects of long-term consumption of a green coffee/roasted coffee blend (35:65) in a randomized, controlled, crossover study on glucose metabolism and measures of insulin resistance in 52 individuals.(4)
Participants consumed the coffee blend three times daily for eight weeks. At the end of the study, coffee consumption led to significant reductions in fasting glucose and HOMA-IR, a measure of insulin resistance, while the researchers also noted improved insulin sensitivity. Based on the results of the study, the authors postulate that regular consumption of the coffee blend may turn out to be an effective recommendation to prevent conditions such as type 2 diabetes and reduce overall cardiovascular risk.
4. SarriÃ¡ B et al., “Long-term consumption of a green/roasted coffee blend positively affects glucose metabolism and insulin resistance in humans,” Food Research International, vol. 89, no. 2 (November 2016): 1023-1028
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Enhanced Liver Support
Recent lines of research suggest that coffee consumption may confer protective effects on liver health and function. Coffee is a source of a number of bioactive compounds, including methylxanthines (like caffeine), amino acids, and polyphenols, which all may contribute to health benefits. Given earlier research indicating liver-health benefits associated with coffee consumption, Iranian researchers sought to evaluate the benefits of green coffee bean extract in patients with non-alcoholic fatty liver disease (NAFLD). (5)
The double-blind, placebo-controlled study included 44 individuals with NAFLD who were asked to consume green coffee bean extract (1 g/day, standardized to 50% chlorogenic acids) or a placebo for eight weeks. All participants were also advised to follow a standardized diet and physical activity program. Liver ultrasound was conducted at baseline as well as at the end of the study, while blood markers of liver function, antioxidant capacity, inflammation, insulin resistance, and cholesterol were also assessed.
After eight weeks of supplementation, there were no differences in ultrasound results between the two groups; however, the green coffee extract significantly improved levels of AST (an enzyme marker of liver function), triglycerides, total cholesterol, fasting blood sugar, C-reactive protein (a marker of inflammation), insulin resistance, and total antioxidant capacity, compared to placebo. These improvements indicate that green coffee extract beneficially supports metabolic function and liver health in individuals with NAFLD.
5. Shahmohammadi HA et al., “Effects of green coffee bean extract supplementation on patients with non-alcoholic fatty liver disease: a randomized clinical trial.” Hepatitis Monthly. Published online March 26, 2017.
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Blood Pressure and Weight Maintenance
Previous clinical studies have indicated the ability of chlorogenic acids to support healthy blood pressure, namely by increasing the bioavailability of nitric oxide and improving endothelial function.(6) In a recent pilot clinical study, researchers sought to analyze the short-term benefits of green coffee extract on blood pressure and weight maintenance, both of which are related to stress, in healthy Jordanian volunteers.(7)
The single-blind, crossover study design looked at the effects of supplementation with green coffee extract (containing 500 mg of chlorogenic acids/day) or placebo for one week, followed by a one-week washout period. Treatments were then switched and supplementation commenced for an additional week.
The results showed that, while no significant changes were evident in the placebo group, green coffee extract supplementation led to statistically significant reductions in diastolic blood pressure levels (a mean decrease of 4.3 mm Hg) and systolic blood pressure levels (a mean decrease of 4.6 mm Hg) after only seven days. Additionally, the researchers found significant reductions in body mass index (BMI) and body weight with green coffee extract compared to no significant differences in the placebo group.
While these results are preliminary, and the study included only 16 subjects, the findings indicate that supplementation with green coffee may yield significant benefits for blood pressure and body weight maintenance within a short period of time.
6. Rodrigo R et al., “Beneficial effects of chlorogenic acids on essential hypertension,” International Journal of Food and Nutritional Science, vol. 3, no. 2 (2016):1-5
7. Al-Dujaili AS et al., “Effect of green coffee bean extract consumption on blood pressure and anthropometric measures in healthy volunteers: a pilot crossover placebo controlled study,” Jordan Journal of Pharmaceutical Sciences, vol. 9, no. 3 (September 2016): 181-191
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