Q. I heard that drinking coffee can cause calcium loss from the body. Is that true?
A. Lydia Fernandes, a dietetic intern at Frances Stern Nutrition Center at Tufts Medical Center, says: "Caffeine, one component of coffee, is the focus of this concern (since it may slightly increase calcium excretion). Research suggests this primarily may be relevant in people who don’t meet their RDA for calcium."
Researchers recently reviewed the science on caffeine and bone health in Food and Chemical Toxicology. They found that moderate caffeine intake (less than 400 milligrams per day, which is equivalent to no more than four 8-ounce servings of regular coffee), regardless of the source, was associated with little effect on calcium balance or bone health in healthy adults, particularly if they were consuming enough calcium.
In an observational study that looked specifically at high coffee intake (4 or more cups daily) versus a low intake (less than 1 cup daily), a high intake was associated with a 2 to 4% lower bone density compared to a low intake. But, this did not translate into an increased risk of bone fracture. The study was published in the American Journal of Epidemiology.
Keep in mind, most of the evidence on this topic is observational, and further research is needed. Whether or not you drink a couple of cups of coffee (or other caffeine-containing beverages) daily, it's important to make sure you're meeting your calcium needs. The calcium RDA for adults is 1,000–1,200 milligrams per day, based on your age and sex.
To learn more: Food and Chemical Toxicology, April 2017