According to the National Institutes of Health, approximately 43 percent of Americans (including almost 70 percent of older women) take dietary supplements containing calcium. But failing to balance calcium with magnesium may actually do more harm than good.

Most people, including many medical doctors, do not understand certain key facts about calcium and its sister mineral, magnesium. 

When everything is in proper balance, magnesium helps the body to absorb and metabolize calcium. Unfortunately, American diet and supplementation practices lead to overconsumption of calcium, and soil depletion and processing of foods lead to underconsumption of magnesium. 

The problem with this is that excess calcium intake can cause problems in the body. The National Institutes of Health Office of Dietary Supplements reports that less than half of calcium people ingest is actually absorbed in the gut. The rest may be excreted, or it can linger in the body to form kidney stones or cause calcification (hardening) in soft tissues.

In addition, numerous studies have shown that magnesium converts vitamin D into its active form so it can aid calcium absorption. Magnesium also stimulates the hormone calcitonin, which helps preserve bone structure and draws calcium out of the blood and soft tissues back into the bones, lowering the likelihood of osteoporosis, some forms of arthritis, heart attack and kidney stones.

A growing amount of scientific evidence, including a 2004 study published in the British Medical Journal, points to high calcium/low magnesium intake leading to calcification, or hardening, of arteries (also known as atherosclerosis, which can cause heart disease, the leading cause of death in the U.S.), osteoporosis and osteoporotic bone fractures.

Why the imbalance?

Recommendations for calcium intake vary greatly across the globe. In the U.S., adults are advised to consume 1,000 mg (or up to 1,500 mg for women over 50) of calcium daily. The U.K. recommends 700 mg daily, while the World Health Organization recommends only 400 to 500 mg daily.

Many people take supplements providing these high levels of calcium without considering the amount they consume through diet, both from food sources and from water (some tap and mineral waters). The typical American diet, especially when it contains dairy products, is high in calcium. The result? A greater amount of unabsorbed calcium in the body. 

The calcium-to-magnesium ratio commonly accepted by health professionals (and seen in many dietary supplements) is 2:1, but this is based on a flawed understanding of the body’s needs. It traces back to the French scientist Dr. Jean Durlach, who proposed the ratio as an outermost, not-to-be-exceeded level when considering calcium intake from all sources (food, water and supplements). This has been largely misunderstood and is taken as a recommendation of a 2:1 calcium-to-magnesium ratio in dietary supplements.

The fact that most people do not meet the minimum daily requirement for magnesium exacerbates the situation. The high-calcium/low-magnesium diet of most Americans, when coupled with calcium supplementation, can skew the ratio to 4:1 or 5:1—or even higher—increasing risk of impaired bone health and heart disease.

Striking a balance

The key to calcium-magnesium balance is at the cellular level. Calcium’s effectiveness and benefits with respect to bone health and the prevention of osteoporosis are enormously impaired unless the body maintains adequate magnesium levels. Unfortunately, it is difficult to get enough magnesium through diet to even meet the minimum RDA requirements because it has been farmed out of the soil and eliminated from most processed foods. 

I recommend monitoring dietary calcium intake, supplementing with vitamin D3, getting the minimum daily requirement of magnesium and aiming for a 1:2 or at least a 1:1 calcium-magnesium ratio.

If you plan to supplement with magnesium, I recommend building up to 300 mg daily. Magnesium supplements are safer than calcium supplements, because magnesium is excreted more completely and doesn’t build up in the body.

The only people who should avoid self-administering magnesium are those with heart block (the type that requires a pacemaker), myasthenia gravis (because their muscles are already too relaxed) or bowel obstruction, and people who are on kidney dialysis.

For more information on magnesium, visit the nonprofit educational resource site www.nutritionalmagnesium.org.