Calcium and Magnesium--Should They Be Taken Together in the Same Supplement?
This article was written by Richard Conant, a nutritionist and consultant to Doctor’s Best.
"Make sure you take magnesium with your calcium, because you need magnesium to absorb calcium!"
This often-repeated nutritional advice has led some Doctor's Best customers to ask why we offer separate calcium and magnesium supplements: High Absorption calcium and High Absorption Magnesium. "Why don't you have one product that gives me both the calcium and magnesium? Don't you need to take them together to absorb calcium?
The answer is: you do not need to take magnesium and calcium together in the same supplement to absorb calcium. The confusion arises from misunderstanding the difference between metabolism and absorption. The body needs magnesium to properly use calcium, in other words to metabolize calcium. But this has to do with what happens to calcium after it has been absorbed, not with calcium absorption itself. Absorption is the process by which a nutrient crosses the intestinal wall and passes into the bloodstream. Calcium absorption is complex and depends on a number of factors. However, the simultaneous presence of magnesium in the gut is not a requirement for calcium absorption.
Magnesium is a crucially important essential mineral, and Doctor's Best has always advocated magnesium supplementation as a high priority, since nutritional surveys consistently show that the average person consumes less than the Recommended Daily Intake (RDI).
Magnesium plays many roles in human physiology, including calcium metabolism. Magnesium deficiency impairs secretion of PTH (parathyroid hormone) the hormone that increases absorption of calcium in the gut by activating vitamin D.1 (PTH also triggers release of calcium from bone when the blood levels of calcium fall too low to meet the body's physiological calcium requirements.) At the same time, activation of vitamin D3 requires magnesium, because the enzyme that catalyzes this activation needs magnesium to work.
Calcium is important for cellular functions, but excess calcium inside the cell can be harmful. Magnesium prevents excess calcium from accumulating inside cells. Interestingly, when cells contain too much calcium, the blood may not have enough. Low blood calcium, know as "hypocalcemia," is a known consequence of magnesium deficiency.2
So, the importance of magnesium cannot be understated. The bottom line is that we need magnesium to make proper use of calcium. In fact, taking calcium supplements may increase the need for magnesium by increasing the proportional intake of calcium relative to magnesium. Many people, especially seniors, consume less than the RDI, as shown in nutritional surveys.3 Taking 1000 mg of or more of calcium in supplements, as is widely recommended, may raise the calcium to magnesium intake ratio too high, unless magnesium is also supplemented.4
Calcium absorption is a complex process that is regulated primarily by the amount of calcium present in the blood at any given time.5 When blood calcium drops below a certain level, the parathyroid glands sense this and secrete PTH. PTH then activates vitamin D. Vitamin D triggers synthesis of a specialized protein that grabs onto calcium in the gut and carries it across the wall of the duodenum, the upper part of the small intestine. This process is called "active transport." Calcium can also cross the walls of the lower parts of the small intestine-the jejunum and ileum-by simple diffusion, a "passive" process that needs no carrier protein. It follows that calcium absorption depends on adequate supplies of vitamin D.
Calcium absorption and excretion can be influenced by various dietary factors, including high protein intakes, phytates (substances in grains and