Date Time Caffeine cuts close to bone when it comes to osteoporosis High doses of caffeine (800 mg) can double the amount of calcium lost in the urine. University of South Australia researchers have a bone to pick when it comes to drinking too much coffee as new research finds that excess caffeine may be linked to an increased risk of osteoporosis. Investigating the effects of coffee on how the kidneys regulate calcium in the body, researchers found that high doses of caffeine (800 mg) consumed over a six-hour period almost doubled the amount of calcium lost in the urine. This is the first study to report the impact of high-dose, short-term caffeine intake on renal clearance of calcium, sodium, and creatinine in healthy adults.