For calcium: Take the calcium in this product with food for best absorption, usually once daily except for the day you take risedronate, or as directed by your doctor.

For best absorption, if your daily dose is more than 600 milligrams, then divide your dose and space it throughout the day.

"Others discovered independently that there's an optimal condition where they can have the best absorption," Cao said.

For the best absorption, take no more than 500 milligrams at one time.