Moderate amounts of 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 doctor 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, 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. 
   
  

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