Here’s an excerpt:
Caffeine. Do you often have calcium-rich yogurt for breakfast or take your calcium pill with your morning meal—then wash it down with a big mug of coffee or tea? Caffeine from any source works against strong bones by interfering with calcium absorption and causing more of the mineral to be lost through the urine. Better: Have your morning yogurt with a glass of orange juice instead, since its vitamin C and magnesium improve calcium absorption…or take your supplement in the afternoon or evening, after you’ve finished drinking coffee for the day.