COFFEE: Overview, Uses, Side Effects, Precautions, Interactions, Dosing and Reviews (2024)

Coffee is a popular drink made from the roasted beans of Coffea fruits (Coffea arabica, Coffea canephora). It contains caffeine and chlorogenic acid.

The caffeine in coffee works by stimulating the central nervous system (CNS), heart, and muscles. Chlorogenic acid might affect blood vessels and how the body handles blood sugar and metabolism.

People most commonly drink coffee to increase mental alertness. Coffee is also used for diabetes, cancer, heart disease, high blood pressure, dementia, and many other conditions, but there is no good scientific evidence to support most of these uses.

Don't confuse coffee with other caffeine sources, such as green coffee, black tea, and green tea. These are not the same.

• Mental alertness. Drinking caffeinated coffee throughout the day seems to increase alertness and thinking skills. Caffeine can also improve alertness after sleep deprivation. Even one cup of caffeinated coffee can reduce fatigue and increase alertness.

• Diabetes. People who drink more coffee seem to have a lower risk of developing type 2 diabetes. The risk lowers more with each cup that's consumed. People with type 2 diabetes who drink more coffee might also have a slightly lower risk of dying.
• Heart failure. Drinking caffeinated coffee seems to reduce the long-term risk of heart failure in people who do not have heart disease.
• Death from any cause. Drinking coffee every day is linked to a slightly lower risk of dying from any cause or from heart disease. It's unclear if drinking coffee is linked with a lower risk of death from cancer.
• Parkinson disease. Drinking caffeinated coffee seems to reduce the risk of developing Parkinson disease. The risk lowers more with each cup that's consumed in males, but not in females. Coffee doesn't seem to help prevent Parkinson disease in people who smoke cigarettes.
• Ability to open bowels and pass stool (poop) following surgery. Drinking coffee might speed up the first stool after certain gut surgeries.
• Impaired movement of food through the intestines after surgery. Drinking coffee might prevent the impaired movement of food through the intestines after certain gut surgeries.

• Cancer of the esophagus. Drinking coffee doesn't seem to lower the risk of developing cancer of the esophagus.

There is interest in using coffee for a number of other purposes, but there isn't enough reliable information to say whether it might be helpful.

• Hardening of the arteries (atherosclerosis). The buildup of calcium-containing plaque in the arteries is an early sign of possible atherosclerosis. Drinking coffee doesn't seem to be linked with a lower buildup of calcium-containing plaque in the arteries.
• Irregular heartbeat (atrial fibrillation). Drinking more coffee doesn't seem to be linked to a lower risk of atrial fibrillation.
• Bladder cancer. Drinking coffee doesn't seem to change the risk of bladder cancer.
• Brain cancer. Some early evidence suggests that Asian people who drink more coffee have a lower risk of developing brain cancer. This does not seem to be true for non-Asian people.
• Breast cancer. People who drink more coffee don't seem to have a lower chance of developing breast cancer.
• Heart disease. It is unclear if drinking coffee lowers the chance of developing heart disease. But it might lower the risk for heart failure and the likelihood of death from heart disease.
• Long-term kidney disease (chronic kidney disease or CKD). People who drink coffee seem to have a slightly lower chance of developing CKD. People with CKD who drink coffee might have a slightly lower risk for kidney failure or death due to kidney failure.
• Memory and thinking skills (cognitive function). There is developing evidence that drinking more coffee over a lifetime might improve thinking skills among women older than 80 years of age. Coffee also might improve the thinking speed and certain types of memory in healthy adults.
• Colon cancer, rectal cancer. There is some evidence that Japanese people who drink more coffee have a lower chance of developing colon or rectal cancer. But research conducted in North America and Europe has not found a link between drinking coffee and the risk of colon and rectal cancer. Drinking more coffee seems to slightly reduce the risk of death in people who have colon or rectal cancer.
• Diseases, such as Alzheimer disease, that interfere with thinking (dementia). People who drink more coffee don't seem to have a lower chance of dementia.
• Depression. People who drink more coffee might have a lower chance of depression.
• Cancer of the lining of the uterus (endometrial cancer). The effect of coffee on the risk of endometrial cancer is unclear. Some research suggests that women who drink more coffee have a lower risk of developing endometrial cancer. But other research has not found a link between drinking coffee and the risk of endometrial cancer.
• Gallbladder disease. People who drink beverages such as coffee that provide at least 400 mg of caffeine per day seem to have a lower risk of developing gallstones. The greater the intake of caffeine, the lower the risk.
• Stomach cancer. People who drink more coffee don't seem to have a lower risk of stomach cancer.
• Gout. There is some evidence that both caffeinated and decaffeinated coffee seem to help to prevent gout. But caffeinated coffee seems to work better.
• Hearing loss. Males who drink at least one cup of coffee daily seem to have a slightly lower chance of hearing loss. But drinking coffee doesn't seem to have this effect in females.
• High levels of cholesterol or other fats (lipids) in the blood (hyperlipidemia). Some research suggests that drinking caffeinated coffee seems to reduce levels of total cholesterol, LDL or "bad cholesterol", and blood fats called triglycerides by a small amount. But other research suggests that drinking coffee increases triglyceride and cholesterol levels.
• High blood pressure. People who drink coffee long-term might have a lower risk for high blood pressure. But smoking might eliminate this benefit. Drinking 1-3 cups daily seems to be most beneficial.
• Low blood pressure. Drinking caffeinated beverages like coffee seems to increase blood pressure in elderly people who experience dizziness after meals due to low blood pressure.
• Kidney failure. People with long-term kidney disease who drink coffee seem to have a slightly lower chance of kidney failure or death due to kidney failure.
• Liver cancer. People who drink more coffee might have a lower risk of liver cancer.
• Liver disease. People who drink more coffee might have a lower risk of liver disease.
• Lung cancer. Some research suggests that drinking caffeinated coffee may help to prevent lung cancer, but other research disagrees. It's too early to draw firm conclusions. Meanwhile, some research suggests that drinking decaffeinated coffee may help to prevent lung cancer.
• The most serious type of skin cancer (melanoma). When factors such as age and sun exposure are taken into account, drinking coffee doesn't seem to be linked with a lower chance of developing skin cancer.
• Build up of fat in the liver in people who drink little or no alcohol (nonalcoholic fatty liver disease or NAFLD). It's unclear if drinking coffee reduces the risk of NAFLD.
• Nonmelanoma skin cancer. Some research shows that drinking many cups of coffee per day might reduce the risk of a specific form of skin cancer called basal cell carcinoma. But drinking decaffeinated coffee does not seem to have any effect on skin cancer risk.
• Obesity. The effect of coffee on weight loss in people who are overweight or obese is unclear. Results from research are conflicting. Some research suggests that taking coffee chemicals, called mannooligosaccharides, for 12 weeks might help with weight loss in men, but not women. Drinking a dark roast coffee seems to help reduce food intake and help with weight loss, whereas a light roast coffee does not. Other research suggests that drinking coffee with or without caffeine does not help with weight loss.
• Mouth cancer. People who drink more coffee don't seem to have a lower risk of mouth cancer.
• Ovarian cancer. Drinking coffee doesn't seem to change a person's risk for ovarian cancer.
• Swelling (inflammation) of the pancreas (pancreatitis). Some early research suggests that drinking 3 or more cups of coffee reduces the pancreatitis risk.
• A type of throat cancer (pharyngeal cancer). People who drink more coffee might have a lower chance of developing pharyngeal cancer.
• Prostate cancer. In general, people who drink more coffee seem to have a slightly lower risk of developing prostate cancer that has not spread outside the prostate.
• Thyroid cancer. Drinking more coffee seems to be linked with a lower risk of thyroid cancer.
• Attention deficit-hyperactivity disorder (ADHD).
• Constipation.
• Other conditions.

More evidence is needed to rate the effectiveness of coffee for these uses.

When taken by mouth: Coffee is commonly consumed as a beverage. Drinking coffee in moderate amounts (about 4 cups daily) is likely safe for most people.

Drinking more than 4 cups of coffee daily is possibly unsafe. Drinking large amounts might cause side effects due to the caffeine content. These side effects can range from mild to serious and include headache and irregular heartbeat.

When given as an enema (rectally): Coffee is possibly unsafe. Coffee enemas have been linked to cases of severe side effects, including death.