Quick Answer
Eating small amounts of coffee grounds is likely safe, but eating large amounts may cause side effects like stomach upset, constipation, and mineral deficiencies. Coffee grounds are high in fiber, minerals, and antioxidants, but also contain caffeine and antinutrients.
What Are Coffee Grounds?
Coffee grounds are the solid remains left over after brewing coffee. They mainly consist of insoluble fiber, antioxidants, caffeine, minerals, and other plant compounds:
Insoluble Fiber
Coffee grounds are approximately 50–70% insoluble fiber, a type of fiber your body can’t digest (1).
Insoluble fiber helps move material through your digestive tract and promotes regular bowel movements and a healthy gut.
Antioxidants
Coffee grounds are very high in antioxidants, including polyphenols, hydrocinnamic acids, and melanoidins (2).
Antioxidants help reduce oxidative stress and inflammation in your body.
Caffeine
Used coffee grounds still contain some caffeine — about 0.4–0.7% by weight.
For comparison, brewed coffee contains about 1% caffeine by weight (3).
Caffeine is a stimulant linked to increased alertness and focus.
Minerals
Coffee grounds are a good source of several minerals, including (4):
– Potassium: A mineral involved in muscle contractions, fluid balance, nerve signals, and blood pressure.
– Magnesium: An important mineral with roles in over 300 enzyme reactions. It contributes to muscle, nerve, and heart health.
– Phosphorus: Works closely with calcium to help build and maintain strong bones and teeth.
– Copper: Required for energy production, connective tissue formation, iron metabolism, and brain development.
– Manganese: An essential trace mineral needed for nutrient metabolism, bone health, and blood sugar control.
Other Plant Compounds
Coffee grounds also contain many other plant compounds like chlorogenic acids, coumaric acids, and phytic acid (5).
However, the health effects of these specific compounds are still unclear.
Potential Benefits of Coffee Grounds
Some research shows that consuming coffee grounds may offer certain benefits:
May promote regularity
The insoluble fiber in coffee grounds can help promote regular bowel movements and relieve constipation.
One study found that supplementing your diet with coffee grounds may be even more effective at treating constipation than wheat bran, a common source of insoluble fiber (6).
May support gut health
The fiber and antioxidants in coffee grounds could benefit gut health in a few ways.
First, insoluble fiber feeds healthy gut bacteria in your colon, which helps maintain the balance of bacteria in your digestive tract (7).
Second, antioxidants like chlorogenic acids and caffeic acids have anti-inflammatory effects in your GI tract and may protect against inflammatory bowel diseases (8).
May reduce cholesterol
Some research indicates that the antioxidants and plant compounds in coffee grounds could reduce LDL (bad) cholesterol and triglycerides (9).
One study found coffee grounds reduced cholesterol by up to 8% in patients with elevated levels (10).
May stabilize blood sugar
In animal and test-tube studies, coffee grounds have been shown to inhibit alpha-glucosidase, an enzyme that breaks down carbs in your gut (11).
This effect may slow the absorption of sugar into your bloodstream after a carb-containing meal and stabilize blood sugar levels. However, this hasn’t been confirmed in human studies yet.
May suppress appetite
Coffee grounds still contain caffeine, a stimulant linked to suppressing appetite and promoting feelings of fullness (12).
One small study showed that people ate less at a meal when they had consumed coffee grounds beforehand compared to when they had consumed regular coffee (13).
The coffee grounds likely promoted greater feelings of fullness. More studies are needed.
Potential Downsides
While small amounts of grounds are likely safe, eating too much may cause adverse effects like:
Nutrient deficiencies
Coffee grounds contain phytic acid, an antinutrient that impairs your absorption of important minerals like iron, zinc, magnesium, and calcium (14).
Eating more than 2–4 tablespoons (30–60 grams) per day could increase your risk of nutrient deficiencies if you don’t eat enough mineral-rich foods.
Constipation and bowel obstruction
Too much insoluble fiber without enough fluids can lead to constipation. Very high intakes may also obstruct your bowels.
Stick to 1–2 tablespoons (15–30 grams) per day — and always drink plenty of water when increasing your fiber intake.
Medication interactions
The caffeine in coffee grounds could interact with certain medications.
Be mindful of your caffeine intake from grounds if you take stimulant or anxiety medications, as caffeine can increase side effects (15).
Heartburn
Coffee grounds are highly acidic. Consuming too much could irritate your stomach lining and trigger heartburn in those with reflux or ulcers.
It’s best to limit your intake to 1 tablespoon (15 grams) at a time and avoid grounds entirely if you have frequent heartburn or GERD.
Bitter, harsh taste
On their own, coffee grounds have a bitter, harsh taste that you may find unpleasant — especially in large amounts.
Consider mixing small amounts into smoothies or healthier baked goods to disguise the strong flavor.
How Much Can You Safely Eat?
Currently, there are no official recommendations for consuming coffee grounds.
Based on research, the following amounts are likely safe for most healthy adults:
– 1–2 tablespoons (15–30 grams) per day: Unlikely to cause side effects and may provide health benefits.
– 2–4 tablespoons (30–60 grams) per day: May cause minor digestive side effects. Only consume this amount consistently if you have no side effects.
– More than 4 tablespoons (60 grams) per day: Likely to cause constipation, nutrient deficiencies, medication interactions, and other adverse effects in the long term. Only eat this amount occasionally.
To be safe, start with just 1 teaspoon (5 grams) at first to assess your tolerance. From there, slowly work your way up to 1–2 tablespoons (15–30 grams) per day.
As with any food, your individual tolerance may vary. Watch out for any digestive issues.
How to Add Coffee Grounds to Your Diet
Here are some ways to add small amounts of coffee grounds to your meals and baked goods:
– Stir 1 tablespoon (8–15 grams) into oatmeal, yogurt, or smoothies.
– Mix 2 tablespoons (15–30 grams) into muffins, cakes, cookie dough, or bread dough.
– Make coffee ground tea by steeping 1 tablespoon (8–15 grams) in hot water for 5–10 minutes. Strain before drinking.
– Fold 1–2 teaspoons (5–10 grams) into chili, sauces, or dressings to add richness.
– Sprinkle 2 teaspoons (6–10 grams) over chocolate to make mocha bark.
– Blend into energy bites or no-bake bars.
– Make DIY exfoliating body scrubs with grounds, oil, and sugar or salt.
Safety and Precautions
Here are some tips to consume coffee grounds safely:
– Stick to 1–2 tablespoons (15–30 grams) per day maximum.
– Start slowly and monitor your tolerance.
– Drink plenty of water to avoid constipation.
– Avoid consuming grounds if you take stimulant medications or have GERD.
– Look for organic, pesticide-free coffee grounds when possible.
– Store unused grounds in an airtight container away from heat, air, light, and moisture.
– Compost wet grounds or use them to fertilize houseplants. Don’t dump them down your sink.
The Bottom Line
Eating a small amount of coffee grounds — about 1–2 tablespoons (15–30 grams) per day — is likely safe for most people and may provide a few health benefits.
However, eating too much may cause side effects, including constipation, nutrient deficiencies, heartburn, and medication interactions.
Enjoy coffee grounds in moderation as part of a balanced diet, and be mindful of your individual tolerance and diet needs. Speak to your healthcare provider if you have any concerns.