Q My doctor reviewed all of my supplements and commented that everything was excellent except for my calcium supplement, 3-Way Calcium Complex. She said it did not contain magnesium, which is necessary for the calcium to be absorbed efficiently; so I added a magnesium supplement. Later, however, I just changed to a calcium product that includes magnesium. I’m sure Pearson & Shaw omitted magnesium from 3-Way Calcium Complex for a reason, and I thought I would ask what it is.

KATHRYN, Rancho Cucamonga, CAL

A There are several reasons. First, not everyone can take magnesium, especially those with kidney problems. Second, the amount of magnesium in the form of magnesium aspartate that we use (for its optimal properties) is very low. At 9.9% elemental magnesium by weight, one would need to take 4040 mg of the compound to get 400 mg of magnesium (the Daily Value), or to take 8080 mg to get 800 mg. That’s an additional 5–10 capsules per day!

If magnesium (as magnesium aspartate) were included in 3-Way Calcium Complex, you would have to take 9 capsules to get 1000 mg of calcium and 400 mg of magnesium. To get these amounts from 3-Way Calcium Complex (size “00” capsules) and On-Target Magnesium (“0” capsules) individually, you still have to take about that many capsules (4 and 6, respectively), but the important thing is that those who can’t take magnesium are not left without a good calcium formulation that they can take.

Finally, regarding the belief that magnesium is required to enable calcium to be absorbed: although calcium absorption is dependent on vitamin D, it apparently does not depend on magnesium.1 (The two minerals are, however, highly interactive in the circulation and in cellular function.) Conversely, most human studies on the effects of dietary calcium on magnesium absorption have shown no effect,2-4 and one study has reported decreased magnesium absorption rates!5

A final, important point is that some magnesium is needed, along with calcium, boron, and vitamins A, C, and D, for proper bone health.


  1. Spencer H, Fuller H, Norris C, Williams D. Effect of magnesium on the intestinal absorption of calcium in man. J Am Coll Nutr 1994;13(5): 485-92.
  2. Fine KD, Santa Ana CA, Porter JL, Fordtran JS. Intestinal absorption of magnesium from food and supplements. J Clin Invest 1991;88(2):396-402.
  3. Hardwick LL, Jones MR, Brautbar N, Lee DB. Magnesium absorption: mechanisms and the influence of vitamin D, calcium, and phosphate. J Nutr 1991;121(1):13-23.
  4. Spencer H, Lesniak M, Gatza CA, Kramer L, Norris C, Coffey J. Magnesium-calcium interrelationships in man. Trace Subst Environ Health 1978; 12:241–7.
  5. Greger JL, Smith SA, Snedeker SM. Effect of dietary calcium and phosphorus levels on the utilization of calcium, phosphorus, magnesium, manganese, and selenium by adult males. Nutr Res 1981;1:315–25.

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