Coffee has been studied in numerous prospective cohort studies and meta-analyses involving large populations. Much of the evidence on long-term disease outcomes is observational, which means it shows associations, not proof of cause and effect:

• Type 2 diabetes: Higher coffee consumption has been associated with a lower risk of developing type 2 diabetes, and some analyses report an inverse dose-response pattern. The size of the association varies across studies and does not establish causation.
• Cardiovascular health: Moderate coffee consumption has generally not been associated with an increased risk of cardiovascular disease in healthy adults, and some studies report lower risks of certain outcomes. Results vary by outcome and population.
• Liver health: Coffee consumption has been associated with lower risks of liver cirrhosis and liver cancer in observational studies. These findings are encouraging but do not establish that coffee prevents liver disease.
• Parkinson’s disease: Coffee intake has been associated with a lower risk of Parkinson’s disease in observational studies.
• Alzheimer’s and dementia: The evidence is inconsistent, and coffee has not been shown to prevent either condition.
• Depression: Some observational studies associate coffee consumption with a lower risk of depression, but the evidence does not establish that coffee prevents depression or improves symptoms.
• All-cause mortality: Several observational studies associate moderate coffee consumption with lower all-cause mortality, without proving that coffee increases lifespan or that one intake level is ideal for everyone.

Coffee also contains chlorogenic acids and other bioactive compounds that contribute to its antioxidant activity. The pattern across studies is genuinely favorable for moderate intake; it is the size and certainty of individual effects that should not be overstated.

Benefits: Caffeine reliably increases alertness and reaction time, and it can improve performance in some forms of exercise, particularly endurance activities. These are the best-established effects of coffee.

• Sleep: Caffeine’s half-life averages around 4–6 hours but varies between individuals. Caffeine later in the day can interfere with sleep, so consider stopping at least 6–8 hours before bedtime, or earlier if you are sensitive.
• Anxiety: Higher doses can worsen anxiety, jitters, and palpitations in susceptible people.
• Pregnancy: ACOG advises limiting total caffeine intake to less than 200mg per day during pregnancy. Caffeine content varies by serving and preparation, and caffeine from tea, chocolate, soft drinks, and other sources counts too. Ask your prenatal care professional if you need individualized advice.
• Blood pressure: Caffeine can temporarily raise blood pressure; the response varies and some tolerance may develop with regular use. People with hypertension should monitor their response and discuss intake with their healthcare professional.

These are examples for typical café servings; actual values vary widely by size and recipe. For many people, plain coffee is a low-calorie drink. Added sugar, syrups, cream, and large servings can raise its calorie content substantially, while caffeine itself may cause side effects in sensitive individuals. Check the nutrition information for your usual order.

Coffee often provides more caffeine per typical serving than green tea, which can make it more convenient before exercise. Both drinks can fit into a healthy diet. Their effects on sleep depend on caffeine content, serving size, timing, and individual sensitivity, so choose based on tolerance and preference.

Mostly yes. Decaffeinated coffee retains many of coffee’s non-caffeine compounds, although amounts vary by product and processing. Some observational studies have also associated decaf consumption with a lower risk of type 2 diabetes, suggesting caffeine alone may not explain the association. Evidence varies by health outcome, and decaf should not be described as proven to prevent disease. Effects that depend on caffeine, such as alertness and some exercise-performance benefits, are generally reduced. The Swiss Water Process uses water-based decaffeination without adding chemical solvents.

Black coffee is low in calories, and caffeine may temporarily increase energy expenditure and fat oxidation. These effects vary between individuals, are modest, and do not guarantee weight loss; appetite effects are also unreliable. For weight management, what matters is the whole diet, including the calories in milk, syrups, and sugar added to coffee. A daily large flavored latte can add several hundred calories, which adds up across a week.

Black coffee contributes very few calories, so it does not add much energy toward a weight-gain goal. If you find coffee reduces your appetite, consider having it between meals rather than immediately before eating. A latte made with whole milk can provide additional calories and some protein, with amounts depending on serving size and preparation.

Caffeine can improve performance in some forms of exercise, particularly endurance activities, although effects vary by person and workout. Sports nutrition studies commonly use 3–6mg of caffeine per kilogram of body weight, often about 60 minutes before exercise. That is a research dose, not a requirement: coffee’s caffeine content varies, so one or two cups may not reliably supply it, and higher doses can cause anxiety, jitters, or poor sleep. Use a lower dose, or skip caffeine, if it causes side effects.

• Paper filters: Paper filters remove much of the cafestol and kahweol in coffee. These compounds can raise blood cholesterol, so paper-filtered coffee may be preferable if you are managing LDL cholesterol. Unfiltered methods such as French press leave more of them in the cup.
• Temperature: Let coffee cool before drinking it. Regularly drinking very hot beverages, particularly above 65°C (149°F), has been associated with an increased risk of esophageal cancer. The concern is the temperature of the beverage, not coffee itself.
• Timing: There is no well-established need to wait 60–90 minutes after waking to drink coffee. Choose a time that suits your routine and caffeine sensitivity, and avoid timing that interferes with sleep.