Coffee, a globally cherished beverage, stems from roasted coffee beans and boasts epidemiological studies suggesting reduced risks of cardiovascular disease, cancers, and non-alcoholic fatty liver disease. However, the post-brewing product, spent coffee grounds (SCG), has received less attention, despite containing bioactive compounds similar to the beverage itself. This article explores the potential benefits and risks of consuming coffee grounds, along with their various practical applications.
What Are Coffee Grounds?
Coffee grounds are the byproduct of the coffee brewing process. They form when whole coffee beans are ground into a fine powder, facilitating flavor and oil extraction during brewing.
Coffee Grounds vs. Coffee Beans
Both coffee grounds and coffee beans contain bioactive compounds like caffeine, chlorogenic acids, and polyphenols, offering health benefits such as improved metabolic parameters and an enhanced gut microbiome. However, they differ in form and processing. Coffee beans are unprocessed seeds typically dried, roasted, and brewed to make coffee, and they can be consumed whole or in the form of chocolate-covered coffee beans.
Nutritional Composition of Coffee Grounds
SCG contains similar bioactive compounds as the beverage, including caffeine, chlorogenic acids, trigonelline, polyphenols, and melanoidins, which have established health benefits and are safe for human consumption. After roasting, coffee powder contains carbohydrates (38-42%), proteins (8-14%), phenolic compounds (3-4%), lipids (11-17%), minerals (5%), fatty acids (3%), caffeine (1-2%), and trigonelline (1%). SCG remaining after the production of hot-brew coffee includes carbohydrates such as 8-15% celluloses and 30-40% hemicelluloses, 20-30% lignins, 7-21% lipids and minerals, and 13-17% proteins, together with phenolic compounds (12 mg/g), caffeine (14.5 µg/g), and CGA (31.8 µg/g).
Potential Health Benefits of Eating Coffee Grounds
While few studies have directly investigated the health effects of SCG consumption, research on coffee as a beverage and the compounds found in SCG suggests several potential benefits:
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- Antioxidant Powerhouse: Coffee grounds are packed with antioxidants, including caffeic acid, which helps reduce premature cell aging and boost collagen levels. Spent coffee grounds contain high levels of phenols. Chlorogenic acid, the most abundant polyphenol, combats inflammation and may protect against diabetes, with some studies even hinting at its potential in battling cancer. Coffee beans boast over six different antioxidants, including cafestol, trigonelline, melanoidins, quinine, and caffeine itself.
- Boosts Brain Function: The caffeine in coffee grounds can improve memory, alertness, mood, energy, and vigilance. Caffeine plays a pivotal role in memory consolidation, effectively reducing forgetfulness for up to 24 hours after consumption. Regular caffeine consumers may also have potential protective effects against neurodegenerative disorders like Alzheimer's and Parkinson's.
- Weight Management: Compounds in coffee grounds can boost metabolism and manage weight by helping with fat oxidation and appetite suppression. Higher coffee consumption, especially among men, could potentially lead to reduced body fat.
- Liver Health: Eating coffee grounds has been linked to a lower risk of liver diseases, such as cirrhosis and liver cancer. It can also help reduce inflammation and fat buildup in the liver. Consuming more than two cups of coffee daily is associated with a reduced likelihood of liver scarring and liver cancer among individuals with liver disease. Increased coffee consumption is also linked to a decreased mortality risk from chronic liver disease.
- Reduces the Risk of Type 2 Diabetes: Eating coffee grounds has been associated with a reduced risk of type 2 diabetes by improving insulin sensitivity and regulating blood sugar levels. For each cup of coffee consumed daily, there was a 6% decrease in the risk of developing type 2 diabetes.
- Cardiovascular Health: Coffee eating, when done in moderation, may have a protective effect on the cardiovascular system by helping lower the risk of heart disease, stroke, and high blood pressure.
- Anti-Inflammatory Properties: Coffee beans have anti-inflammatory properties, which can help reduce inflammation by blocking a specific gene throughout the body.
- Mood Enhancement: The caffeine in coffee beans is known to elevate mood and reduce the risk of depression by increasing the release of neurotransmitters like dopamine and serotonin, which contribute to feelings of well-being.
- Performance-Boosting Powers of Caffeine in Exercise: Caffeine can reduce post-exercise muscle pain and enhance endurance, reduce perceived exertion, and improve physical performance, gait speed, power output, and time-trial completion time.
Potential Risks and Side Effects of Eating Coffee Grounds
While eating coffee grounds offers some health benefits, there are potential risks and side effects to consider:
- Excessive Caffeine Intake: High caffeine intake can lead to increased anxiety, palpitations, and sleep disturbances. It is also linked to withdrawal symptoms like headaches, nausea, and poor concentration.
- Digestive Issues: The caffeine and other compounds in coffee grounds can cause stomach upset, heartburn, and increased bowel movements.
- Increased Cholesterol Levels: Coffee grounds contain diterpenes such as cafestol and kahweol, which can raise cholesterol levels. Unfiltered coffee tends to have a higher concentration of these diterpenes.
- Heartburn and Stomach Upset: Certain compounds in coffee beans can increase stomach acid, leading to heartburn, bloating, nausea, and stomach upset.
- Laxative Effect: Caffeine can increase bowel movements, and even low doses of caffeinated coffee may cause diarrhea.
- Sleep Disturbance: Caffeine can lead to sleep problems, particularly in caffeine-sensitive individuals, making it difficult to fall and stay asleep.
- Other Potential Side Effects: High caffeine intake is linked to increased anxiety symptoms, withdrawal symptoms, and an increased risk of pregnancy problems.
Moderation and Safe Consumption
The number of coffee beans you can safely consume comes down to a safe level of caffeine. Although tolerance to caffeine varies, doses up to 400 mg per day - around 4 or 5 cups of coffee - are considered safe for healthy adults. On average, a chocolate-covered coffee bean contains around 12 mg of caffeine per bean, meaning that adults can eat around 33 chocolate-covered coffee beans without going over the recommended safe level of caffeine.
Practical Applications of Spent Coffee Grounds (SCG)
Beyond potential health benefits, SCG has various practical applications:
- Industrial Uses: SCG can be used as a valuable industrial resource for purifying compounds for therapeutic studies and providing financial support for these studies.
- Biodegradable Films and Coatings: Polysaccharide-rich fractions in SCG provide viscous and stable liquid solutions suitable for use as raw materials for biodegradable films or coatings for packaging.
- Agriculture: SCG contains nitrogen and other important minerals required in both compost and fertilizers, and so could be used by the agriculture industry.
- Biofuels: Biofuels such as bioethanol, biogas, and biodiesel can be produced from SCG, thus redirecting large amounts of coffee waste as a sustainable source of biofuel.
- Pharmaceutical Products: SCG may be an efficient, low-cost, and environmentally friendly source of antioxidants, polyphenols, and biomaterials for pharmaceutical products.
- Food Additives: SCG, along with other coffee plant wastes, have been successfully used as a sustainable, cost-effective, and healthy food additive in baked products, granolas, slow-cooked meals, seasoning for barbecues, and desserts.
- Extraction of Valuable Compounds: SCG can be used as a raw material for the isolation of compounds like caffeine, polyphenols such as CGA, and melanoidins using various extraction methods.
- Biorefinery: Biorefinery using SCG can provide many valuable products, including biodiesel, hydrocarbon fuel, bio-hydrogen, glycerine, many pharmaceutical-grade bioactive compounds, bioethanol, bio-oil, biochar, polymers, and biogas.
- Skin Exfoliation Product: People can mix coffee grounds with water, honey, or coconut oil to create a skin scrub that they can use all over the body.
- Natural Dye: Coffee grounds can dye natural fabrics to different shades of tan and brown.
- Fertilizer: Coffee grounds can conserve the nitrogen content of soil, which may benefit plant growth.
- Insect Repellent: Coffee contains diterpenes, which are toxic to insects, making coffee grounds a suitable insect repellent for a person’s garden.
- Flea Repellent: Rubbing coffee grounds into a pet’s fur may help repel fleas.
- Cleaning Product: Coffee grounds are abrasive and can be used to scrub surfaces, utensils, or appliances that have ingrained or hard-to-remove dirt.
- Odor Reliever: Coffee grounds can neutralize odors on the hands after cooking or minimize odors in shoes.
- Meat Tenderizer: Coffee grounds are acidic and contain enzymes that can break down fibers in meat, making it softer and easier to eat.
- Furniture Restoration Product: Mixing coffee grounds with water can create a paste that can be rubbed into scratches on wooden furniture to match the original color.
How to Incorporate Coffee Grounds into Your Diet
While coffee grounds' health benefits are compelling, consuming them in moderation is essential. Here are a few ways to incorporate coffee grounds for eating:
- Munch on Roasted Beans: You can roast coffee beans at home or purchase pre-roasted ones. Munch on a small handful as a snack or mix them into trail mix.
- Coffee Flour: Coffee flour is made from the pulp of coffee cherries and is a versatile ingredient in baking. It imparts a subtle coffee flavor and an extra dose of antioxidants to your recipes.
- Coffee Smoothies: Add a teaspoon of finely ground coffee beans to your morning smoothie for a unique flavor and an energy boost.
- Coffee Seasoning: Ground coffee beans can be used as a seasoning for meats, especially for barbecue or grilling.
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