Caffeine Myths and Facts
Caffeine Myth No. 2: Caffeine Is Likely to Cause Insomnia
Your body quickly absorbs caffeine. But it also gets rid of it quickly. Processed mainly through the liver, caffeine has a relatively short half-life. This means it takes about five to seven hours, on average, to eliminate half of it from your body. After eight to 10 hours, 75% of the caffeine is gone. For most people, a cup of coffee or two in the morning won't interfere with sleep at night.
Consuming caffeine later in the day, however, can interfere with sleep. If you're like most people, your sleep won't be affected if you don't consume caffeine at least six hours before going to bed. Your sensitivity may vary, though, depending on your metabolism and the amount of caffeine you regularly consume. People who are more sensitive may not only experience insomnia but also have caffeine side effects of nervousness and gastrointestinal upset.
Caffeine Myth No. 3: Caffeine Increases the Risk of Osteoporosis, Heart Disease, and Cancer
Moderate amounts of daily caffeine -- about 300 milligrams, or three cups of coffee -- apparently cause no harm in most healthy adults. Some people are more vulnerable to its effects, however. That includes such people as those who have high blood pressure or are older. Here are the facts:
Osteoporosis and caffeine. At high levels (more than 744 milligrams/day), caffeine may increase calcium and magnesium loss in urine. But recent studies suggest it does not increase your risk for bone loss, especially if you get enough calcium. You can offset the calcium lost from drinking one cup of coffee by adding just two tablespoons of milk. However, research does show some links between caffeine and hip fracture risk in older adults. Older adults may be more sensitive to the effects of caffeine on calcium metabolism. If you're an older woman, discuss with your health care provider whether you should limit your daily caffeine intake to 300 milligrams or less.
Cardiovascular disease and caffeine. A slight, temporary rise in heart rate and blood pressure is common in those who are sensitive to caffeine. But several large studies do not link caffeine to higher cholesterol, irregular heartbeats, or an increased risk of cardiovascular disease. If you already have high blood pressure or heart problems, though, have a discussion with your doctor about your caffeine intake. You may be more sensitive to its effects. Also, more research is needed to tell whether caffeine increases the risk for stroke in people with high blood pressure.
Cancer and caffeine. Reviews of 13 studies involving 20,000 people revealed no relationship between cancer and caffeine. In fact, caffeine may even have a protective effect against certain cancers.