Coffee and Calcium Loss

By Robert H. Shmerling, M.D., Harvard Medical School, for MSN Health & Fitness

Q: For years I have read that drinking coffee may lead to calcium loss in the bones and worsen osteoporosis. Is this true?

A: Osteoporosis is a condition marked by reduced bone strength and an increased risk of fracture. Aging and, in women, the loss of estrogen during menopause are major risk factors.

Other risk factors include:

• Female gender (although osteoporosis is also common among men over the age of 70)
• Sedentary lifestyle
• Low intake of calcium and vitamin D
• Smoking
• Excessive alcohol intake
• Taking a glucocorticoid (steroid) medication
• Family history of osteoporosis
• Prior low-impact fracture
• Low body weight (especially if it leads to loss of menstrual periods)
• An overactive thyroid (or taking too much thyroid medication)

Coffee intake is not considered a significant risk factor for osteoporosis. But there has been concern about coffee’s impact on bone strength because coffee can impair absorption of calcium from the digestive tract. This probably matters most when coffee intake is high (e.g., four or more cups of coffee daily) and calcium intake is low.

While many high quality research studies have not found that coffee consumption increases the risk of osteoporosis, a few have suggested otherwise. When a potential risk factor has a modest impact in some studies and no effect in others, it’s probably because the studies used different methods. At any rate, it’s likely that the impact (if any) of coffee on bone strength is small.

It’s tough to study the effect of coffee consumption on the risk of osteoporosis because one must rely on self-reported consumption and because coffee intake alters other risk factors. For example, people who smoke cigarettes also tend to drink lots of coffee; one might conclude that coffee intake increased osteoporosis risk in a particular group of people when it was really the smoking. Also, big coffee drinkers may drink less milk than people who don’t like coffee. In fact, several studies found that the possible negative effects of coffee consumption on bone strength were mostly limited to people with low calcium intake and that the problem could be overcome by increased calcium intake.

The bottom line
There are much more important risk factors for osteoporosis than coffee intake. So, enjoy your coffee and do what you can to modify the other well-established risk factors listed above.

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Robert H. Shmerling, M.D. is associate physician at Beth Israel Deaconess Medical Center and associate professor at Harvard Medical School. He has been a practicing rheumatologist for over 20 years at Beth Israel Deaconess Medical Center.