The 5 Biggest Myths About Caffeine

Caffeine boosts your energy, lifts your spirits and improves your physical and mental performance. But is it bad for you?

Caffeine is considered a drug because it acts as a mild stimulant on the central nervous system. Because of its drug-like action, caffeine has been studied for many years for potential side effects. Researchers have looked at caffeine's possible role in many conditions, from birth defects and osteoporosis to cancer and heart disease. Surprisingly, they found more good than bad. Here's what some people say about caffeine, along with some perspective:

Caffeine is addictive. While it can be habit-forming, and you may feel some minor side effects such as fatigue, drowsiness or headaches if you suddenly stop drinking caffeine-containing beverages, it is not classified as an addictive substance.

Caffeine weakens your bones. The results of studies linking caffeine or coffee to the bone-thinning disease osteoporosis have been mixed. For now, Oregon State University researchers recommend limiting coffee to three cups a day and making sure you get the recommended amounts of calcium and vitamin D.

Caffeine causes heart disease. Not true, although excessive amounts of caffeine-containing beverages have been linked to increased blood pressure and heart rate and, rarely, to detection of an irregular heartbeat. The current thinking in scientific circles is that caffeine, at least in the amounts that come with a cup or two of coffee, may actually do your heart some good.

Caffeine is dehydrating.  This could be true, but the diuretic effects of caffeine-containing drinks that might contribute to dehydration are usually offset by the fluid content of the beverage. Caffeine supplements and caffeine-containing medications also have a diuretic effect, however, so it is important to take them with plenty of fluids.

Caffeine causes cancer. Researchers have looked at possible links between caffeine consumption and lung, bladder, renal, pancreatic and breast cancers and found no overall increased risk. One large-scale Japanese study did find an increased risk of breast cancer development in women with pre-existing non-cancerous breast conditions who drank four or more cups of coffee a day.  However, benign breast disease is itself a risk factor for developing breast cancer.

What researchers have seen for sure in more than 20 years of studying caffeine and caffeine-containing beverages, is that caffeine passes through the placenta and through breast milk, which means it could affect a fetus or newborn baby the same way it affects adults. As a result, pregnant and nursing women are advised to avoid caffeine or drink no more than one cup of coffee a day.

At the same time, Harvard Medical School experts now say that coffee drinkers appear to be less likely to suffer heart attacks and strokes than those who don't indulge. Unless, of course, your java drink is made with espresso, which is brewed without filters. Unfiltered coffee contains substances that can increase your LDL or "bad" cholesterol and, over time, that's not good for anyone's heart.

The lack of serious negative effects and the existence of several positive effects of caffeine are all associated with moderate intake, meaning three or four cups of coffee or 300 to 400 mg of caffeine daily.


University of Illinois at Urbana-Champaign: McKinley Health Center

The Harvard Medical School Health Guide

Oregon State University: Linus Pauling Institute