Optimizing Calcium Supplementation

Q I take a calcium supplement (with added minerals plus vitamin D) containing 1200 mg of calcium. Yet I have been told you should not take more than 500 mg of calcium at a time, as your body does not absorb it. Am I wasting part of my calcium by taking it all at once?

LOU, Tulsa, OK

A Yes. Most experts agree that when you exceed about 500 mg per serving, the percent of calcium absorbed decreases as the amount of calcium in the supplement increases.1 This means that you lose some of the benefit. You’re right to take vitamin D, which can substantially increase calcium absorption. Vitamin D also influences calcium utilization, resulting in reduced rates of bone loss and improvements in bone mass in adults. Furthermore, it operates through several pathways to reduce the risk of fracture. Vitamin D can also improve muscle performance and reduce the risk of falling.

Other nutrients that can help optimize the benefits of calcium are vitamins A and C and the mineral boron. The most bioavailable form of calcium is citrate. However, there are advantages to taking lesser amounts of calcium phosphate and calcium ascorbate as well.

Even though the half-lives of different supplements vary, it is best to take your supplements in evenly divided doses, 3 or preferably 4 times daily. Why? Some of the B-vitamins dissipate by as much as 50% in 3–4 hours, so if you haven’t taken these supplements within the last 5–6 hours, your levels may be suboptimal, leaving you unprotected and at a disadvantage.


  1. Standing Committee on the Scientific Evaluation of Dietary Reference Intakes, Food and Nutrition Board, Institute of Medicine. Dietary Reference Intakes for Calcium, Phosphorus, Magnesium, Vitamin D, and Fluoride. The National Academies Press, Washington DC, 1997.

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