Green coffee is unroasted coffee. The green seeds or "beans" of the coffee cherry are covered in a whitish mucilage, tucked inside the fruit. As health experts tirelessly seek the next great panacea, green coffee continues to gain popularity.
Unlike roasted coffee, green coffee maintains its raw form and has a different chemical profile. It's known for high levels of chlorogenic acid (CGA), a compound purveyed as an aid to weight loss and blood sugar regulation. Chlorogenic acid is an ester of caffeic acid.
Caffeic acid is an antioxidant unrelated to caffeine. While we're on the subject, caffeine is less in a cup of green coffee than in roasted coffee. A cup of green coffee contains 20-50 mg of caffeine. A cup of regular coffee contains approximately 100 mg.
The amount of caffeine in a cup of coffee is determined by the roasting and brewing. During roasting coffee beans release water, making the caffeine in the beans easily extracted when brewed. In contrast, unroasted or green coffee beans release less caffeine on brewing.
However there's more chlorogenic acid in the raw beans, and this is due to the roasting process. Heat can degrade CGA. A report by Blumberg et al shows roasting temperatures inhibit chlorogenic acid precursors, and lower the total extractable CGA concentrations.
Raw green coffee beans are considered edible, acidic with pastoral flavors. They can cause digestive problems. They're harder than roast beans and difficult to chew, not having the crispness or browning Maillard effect of roast coffee. Thus they're usually sold as supplements.
The Biology of Green Coffee
Not surprisingly, green coffee beans come from the coffee plant, primarily Coffea arabica and C. robusta (Coffea canephora var. robusta). Beans of C. robusta have lower acidity, more bitterness, and a woody and less fruity flavor compared to C. arabica beans.
Vietnam tops the robusta records, producing over 90% of the world's consumption. Most of it is used for instant coffee. Chlorogenic acid is present in both types of coffee and also in various foods and plants.
These include apples, bread, artichokes, betel, burdock, carrots, coffee beans, eggplants, grapes, honeysuckle, kiwi fruit, pears, plums, potatoes, black tea, tobacco leaves, tomatoes and wormwood.
Chlorogenic acid neutralizes free radicals, unstable atoms which corrupt cells. Neutralization can prevent DNA damage and potentially guard against carcinogenesis. Also called oncogenesis or tumorigenesis, carcinogenesis is the beginning of cancer formation.
Free radicals damage cells by lipid peroxidation, causing membrane corruption. They affect protein cross-linking, leading to enzyme inactivation; and DNA breaks, which can cause mutations.
CGA is present in higher quantities in green coffee beans than in their roasted counterparts, as the roasting process reduces the levels of this compound. Green coffee also has less caffeine, 25-50% the amount of caffeine as roast coffee.
Content of these active components depends on many factors. These include growing conditions of the coffee plant, soil pH and nitrate or ammonia uptake, type of coffee, climate, fermentation by local yeasts and bacteria, and other manufacturing techniques used.
The combination of CGA antioxidants and caffeine can affect metabolism and overall health. According to the National Institutes of Health (US) chlorogenic acid lowers blood glucose concentrations and inhibits the metabolic pathways releasing glucose from the liver.
Glucose not released from the liver is stored as glycogen, a fat. A buildup of fat causes fatty liver disease.
The Process of Making Green Coffee
Preparing green coffee involves a few distinct steps, differing significantly from the traditional coffee-making process:
Selection
Quality green coffee beans are sourced, often from specialty coffee farms. Beans are chosen based on their origin, species, and processing method. Coffee cherries are picked only when ripe. Harvest is once a year depending on the region, which can lead to significant variations in availability.
Processing uses primarily the dry or wet method, or the honey method which is a combination of the two. In dry method, cherries are sun-dried before removing the outer layers. Wet method includes pulping the cherries, followed by fermentation and washing.
Preparation
The dried beans are hulled to remove remaining parchment, and sorted by size and density. They are usually fermented to varying degrees using different methods before the fruit is washed off. Processed, beans are dried to reach an ideal moisture level for long-term storage.
To consume, the beans are usually soaked in water to soften them. Some green coffee lovers grind the beans to a fine consistency, while others brew them whole.
Brewing
Green coffee can be brewed like regular coffee. Although the beans are green the coffee has an amber color. The most common brew methods include boiling, steeping or French press. Green coffee is brewed longer than roast to extract maximum chlorogenic acids and flavors.
Flavoring
Because green coffee is less aromatic and has a more grassy, herbal flavor than roasted coffee, some people add sweeteners or milk to improve the taste.
Possible Health Benefits
Green coffee has been associated with a variety of possible health benefits marketers love to tout. These include:
Weight Loss: One of the most popular claims surrounding green coffee is its ability to promote weight loss. Chlorogenic acid may help control body fat by quickening metabolic rate and inhibiting fat absorption.
Antioxidant Properties: The high levels of chlorogenic acid in green coffee may provide significant antioxidant benefits, potentially reducing oxidative stress and inflammation in the body.
Blood Sugar Control: Some research indicates green coffee can help regulate blood sugar levels, potentially lowering risk of type 2 diabetes. The number of natural treatments making this claim is immense. Chlorogenic acid is also said to enhance insulin sensitivity and lower glucose absorption.
Cognitive Function: The caffeine content, even if lower than roast coffee, might help stimulate the brain and its processes. However for people with anxiety problems, caffeine can exacerbate them.
One reason for the popularity of green coffee is media manipulation. According to an unsubstantiated study by the Dr. Oz show in 2012, overweight people who consume green coffee extract lose an average of 10% of their body weight over 12 weeks.
Thus, if I'm 200 lb, I would expect to lose 20 lb in 12 weeks or 1.6 lb a week. One to two pounds a week is considered ideal weight loss by the Centers for Disease Control & Prevention when attained through healthy diet and exercise.
Lindsey Duncan, the show's guest, is fined $9 million by the Federal Trade Commission for making misleading and unsupported claims about green coffee products promoted by the show. Regardless, green coffee sales spike dramatically.
Consumer Protection: Warnings and Considerations
Caffeine Sensitivity: People sensitive to caffeine can experience side effects such as jitteriness, mood swings, anxiety or insomnia.
Gastrointestinal Issues: Some patients report stomach discomfort or digestive problems with drinking green coffee. The amount of suffering varies exponentially with the amount of coffee consumed.
Unregulated Supplements: Many green coffee extract supplements on the market are not yet regulated. Quality and efficiency are not standardized and can vary widely.
Consumer Protection: Charges of False Claims
A 2011 review finds tentative evidence that green coffee extract promotes weight loss; quality of the evidence is poor. In 2014, a key trial demonstrating benefits is retracted. The study's sponsor, Applied Food Sciences, is fined by the FTC making unfounded weight-loss claims based on the flawed study.
Fortune magazine reports in June 2014 that benefits of consuming green coffee bean extract is largely disproved by studies to date. In May 2014, the FTC charges the Florida-based manufacturers of Pure Green Coffee with deceiving consumers with false weight loss claims.
On June 17, 2014, a U.S. Senate subcommittee holds hearings to discuss weight-loss products and consumer protection. During the hearings, green coffee extract is cited several times as an example of a "phony" product sold to consumers.
A larger 2017 review assesses the effects of chlorogenic acid, the main phenolic compound in green coffee extract. It determines the human studies to date are of poor quality and no conclusions can be drawn from them. It's up to the consumer to be informed and decide.
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