The attenuated obesity and reduced systolic blood pressure were observed in rats fed a high-carbohydrate, high-fat diet to induce metabolic syndrome—a cluster of conditions that occur together, increasing risk of heart disease, stroke, and type 2 diabetes, according to the Mayo Clinic’s definition.
These improvements came without any changes in glucose homeostasis and plasma lipid concentrations, the researchers added.
“As coffee is one of the most accepted beverages in the world, green coffee has the potential to be developed as a safe dietary supplement to manage weight and blood pressure,” the researchers argued in their study, published this month in the Journal of Functional Foods.
While studies on roasted coffee are abundant (the researchers noted 201 meta-analyses linking it to lower risks of cardiovascular disease, some cancers, and neurological and liver conditions), studies on green coffee are lacking.
For the few that have been published, many researchers, including the Australian authors of this present study, characterized them as poor quality.
Green coffee bean extract was dubbed as a ‘magic, miracle pill’ by Dr Oz in a show that aired in 2012. This caused a spike of searches for the extract, based on Google Trends analysis—but then it only went downhill from there.
Looking at sales data, sales for supplements with the extract fell in the multi-outlet channel (MULO) by almost 41% year-over-year in 2015, according to the 2015 Herb Market Report by HerbalGram. This is the same time period when researchers retracted a study on green coffee bean extract’s benefits, The Washington Post reported.
The retraction led to a $3.5 million fine from the FTC to one green coffee extract supplier.
“However, green coffee could be a cost-effective functional food to reverse or prevent metabolic syndrome, as it contains caffeine, chlorogenic acids and trigonelline,” wrote the Australian researchers.
Study details and results
This latest data on green coffee bean extract was based on an analysis of 72 male rats.
They were divided into six groups and fed for 16 weeks with either 1) corn starch diet alone; 2) corn starch diet with 5% green or 3) decaffeinated green coffee in for the last eight weeks; 4) high-carbohydrate high-fat diet alone; or 5) high carbohydrate and high-fat diet with 5% green or 6) decaffeinated green coffee in food for the last eight weeks.
Characterizing the ingredients, the researchers reported that green coffee contained chlorogenic acids, trigonelline, caffeine and diterpenoids. Decaffeinated green coffee contained these compounds, but no caffeine.
Rats that received the green coffee exhibited less body weight gain, a closer-to-normal systolic blood pressure, and less inflammation in the heart and liver.
They did not find significant differences between caffeinated and decaffeinated supplements. "The responses of green and decaffeinated green coffee were similar except for the increases in plasma triglycerides in decaffeinated green coffee-treated obese rats," they explained. This contradicts results from a previous study done by the same team, where both caffeine and decaffeinated coffee was linked to increases in triglycerides, "thus making it difficult to interpret the main cause of the increase in triglycerides."
“This study, along with some of our previous studies, has now defined the potential health benefits of coffee and coffee components in the same rat model of obesity,” they argued.
Limitations included the absence of other studies using the same model but with trigonelline and diterpenoids alone, making it hard to compare and come to conclusions.
“Moreover, a dose-response study of coffee extract would be able to define if the lower dose of coffee is similarly effective as the dose studied here,” they added.
Source: Journal of Functional Foods
Published online ahead of print, doi.org/10.1016/j.jff.2019.04.003
“Green coffee ameliorates components of diet-induced metabolic syndrome in rats”
Authors: Nikhil S. Bhandarkar