(HealthDay News) -- Many people won't start the day without a cup of coffee.
Caffeine, the stimulant found in coffee, isn't harmful for most people who drink 400 milligrams (mg) or less each day, the U.S. National Library of Medicine says.
The average 8 oz. cup of coffee contains 95 to 200 mg of caffeine, while a 12-ounce energy drink contains 70 to 100 mg.
If you're pregnant, breast-feeding or have conditions including anxiety, ulcers or irregular heartbeat, you probably should limit intake or avoid caffeine altogether, the agency advises.
Here's the NLM's assessment of how caffeine affects the body:
- It stimulates the central nervous system, which can make you feel more awake and give you a boost of energy.
- It is a diuretic, which helps your body get rid of extra salt and water by causing you to urinate more.
- It increases the release of acid in your stomach, which can trigger an upset stomach or heartburn.
- It may interfere with the body's absorption of calcium.
- It increases blood pressure.