Calcium Supplements May Not Be the Way To Healthy Bones After All

 A recent research study on the effects of calcium supplementation on 
bone density, fractures and colorectal cancer yielded some surprising results.

This article, from the Seattle P.I.  2-16-06, reflects a common limitation that is basic to research; you can only study one or two things at a time to truly determine whether the substance being investigated really makes a difference.  In researching the effects of only calcium and vitamin D, this study may have coincidently caused a magnesium deficiency because high blood levels of calcium (hypercalemia), can deplete blood magnesium (hypomagnesemia)  This could lead to a higher risk of osteoporosis, fractures and other health problems.  This may be part of the reason why those in the placebo group had less fractures than those taking calcium and vitamin D..

Recommended Dietary Allowance (RDA) of calcium for adults age 18+ is 1,000 to 1.300 mg per day,  and for magnesium, 400 to 420 mg per day .

Reference Info:

Magnesium, the second most abundant intracellular cation, has been identified as a cofactor in over 300 enzymatic reactions involving energy metabolism and protein and nucleic acid synthesis. Approximately half of the total magnesium in the body is present in soft tissue, and the other half in bone.  The causes of hypomagnesemia (low blood magnesium) are reduced intake, reduced absorption (chronic diarrhea, malabsorption, or gastric or bowel surgery), and increased excretion (medication, alcoholism, diabetes mellitus, renal tubular disorders, hypercalcemia (high blood calcium), hyperthyroidism, aldosteronism, stress, or excessive lactation).  A large segment of the U.S. population may have an inadequate intake of magnesium and may have a chronic latent magnesium deficiency that has been linked to atherosclerosis, myocardial infarction, hypertension, cancer, kidney stones, premenstrual syndrome, and psychiatric disorders (Disease-a-Month :DM, 1988 Apr., 34(4):161-218).

Several factors affect Mg reabsorption in the Kidney. Hypermagnesemia and hypercalcemia inhibit reabsorption leading to increased urinary excretion of Mg and Ca
(de Rouffignac C, Quamme G., Renal magnesium handling and its hormonal control. Physiological Reviews 1994 Apr;74(2):305-22.)

Magnesium deficiency has also been implicated in osteoporosis. The magnesium intake in people with osteoporosis reportedly is lower than in control subjects, and magnesium intake frequently is lower than the recommended dietary intake in many groups, especially elderly persons. Postmenopausal women are often encouraged to consume at least 1000 mg of calcium per day, which leads to altered dietary calcium-to-magnesium ratios. The calcium supplementation may reduce the efficacy of magnesium absorption and further aggravate increased demineralization (of the bones).  In addition, the formation of Clairol (Vit. D) involves a magnesium-dependent hydroxylase enzyme, and concentrations are reduced in magnesium deficiency, possibly affecting calcium reabsorption.  Magnesium supplementation reportedly increases bone density, arrests vertebral deformity, and decreases osteoporotic pain (.Mahendra Agraharkar, MD, & Mark Fahlen, MD,  Hypomagnesemia,

John W. Cartmell, MS 

Calcium Supplements May Not Be the Way To Healthy Bones After All


A large, seven-year study of healthy women over age 50 found no broad benefit from calcium and vitamin D supplements in preventing broken bones, despite widespread endorsement by doctors for the supplements.

The study also found no evidence that the supplements prevented colorectal cancer, and it found an increased risk of kidney stones.

Osteoporosis specialists said the study, published today in the New England Journal of Medicine, is likely to put a dent in what has become a widespread medical practice of recommending that all women take calcium and vitamin D supplements starting at menopause if not sooner, as a sort of insurance policy against osteoporosis. But beyond that there is no agreement on what, if anything, healthy women should do.

The $18 million study was part of the Women's Health Initiative, a large federal project that, last week, reported findings that low-fat diets do not protect against breast or colorectal cancer or heart disease. A few years ago, the initiative's study on hormone treatment after menopause showed it had more health risks than benefits.

And the results from the new study on calcium and vitamin D, like the others, confound popular beliefs and raise questions about public health messages that had been addressed to the entire population.

In every case, the Women's Health Initiative was testing hypotheses that arose from studies that observed populations and correlated certain health practices with medical outcomes. But such observational studies, statisticians agree, can yield misleading information because a group that happens to follow certain health advice may differ in unknown ways from groups that did not. The study's leaders said there were hints of benefits for some subgroups in the study. But the supplements' only positive effect in the overall study population -- 36,282 normal, healthy women ages 50 to 79 -- was a 1 percent increase in bone density at the hip.

The participants were randomly assigned to take 1,000 milligrams of calcium and 400 international units of vitamin D a day, or to take placebos, and were followed for seven years. Researchers looked for effects on bone density, fractures and colorectal cancer. The lack of an effect on colorectal cancer over the seven-year period was so clear that it has aroused little debate. But the effect on bones is another story.

The annual rate of hip fractures in adherent women taking the supplements was 10 per 10,000 as compared with 14 per 10,000 in adherent women taking placebos.  In a separate subgroup analysis of all women in the study older than 60, The rate was 19 per 10,000 in women older than 60 taking the supplements, compared with 24 per 10,000 in women older than 60 taking placebos.

But such subgroup analyses are questioned by many statisticians, who point out that there always will be subgroups in a large study showing one effect or another, simply by chance.

Dori Khakpour, a University of Washington nutritionist, said when looking at studies involving thousands of people, "we're not sure what we're looking at. The answers don't mean what we think they do."

"The question here is what form the calcium came in," Khakpour said. Susan Gins, another Seattle-based nutritionist, had the same question.

"There's a big difference in absorbability of calcium. Calcium citrate is more absorbable than calcium carbonate (the form used in the study)," Gins said.

Nonetheless, said Dr. Elizabeth Nabel, the study's director, the subgroup data and the increase in hip-bone density do indicate the value of adequate calcium and vitamin D.

"Based on all the results, women -- particularly those over 60 -- should consider taking calcium and vitamin D for bone health," she said.

Others were not so sure.

Dr. Ethel Siris, president of the National Osteoporosis Foundation, said the new study has made her question the advice given by many doctors that all women take calcium supplements regardless of what is in their diet. "We didn't think it hurt, which is why doctors routinely gave it," she explained.

The new study, she says, shows it can hurt to take the supplements -- among the women taking them there were five additional cases of kidney stones per 10,000 women per year. So, Siris said, her suggestion is that doctors only urge the supplements upon women who are not getting enough calcium -- 1,200 to 1,500 milligrams a day -- from their diets.

Dr. Clifford Rosen, director of the Maine Center for Osteoporosis Research and Education in Bangor, said he would now reserve the supplements for women older than 70 -- the age group with the greatest risk of hip fractures -- who are not getting enough calcium and vitamin D.

"This is a public health intervention," Rosen said. "We've been recommending it for everyone but it probably doesn't work in the majority of people or the effect is small. And there is an increase in kidney stones. It is not a benign intervention."

Two Seattle-area women who fall into the healthy, 50-to-79 category said they wanted more information. Barbara Fowler has been taking 1,800 milligrams of calcium a day for 15 to 20 years and has had bone loss and osteoporosis. She also takes two other drugs to help her assimilate the calcium. "I've been told by my doctor that calcium intake has nothing to do with kidney stones," Fowler said. She is going to seek more information.

Lou Lorton said she's been taking 500 milligrams of calcium per day for about six years. "That's not sufficient for a woman my age, but I feel I make up the difference with dietary calcium -- yogurt, cheese, milk and green vegetables."

Lorton said she isn't likely to change her habits, but she would question the study. "I don't know anything about it at this point," she said.

The study's investigators realized that they would be applying the cold light of science to popular messages that have fueled a booming calcium-supplement industry, with annual sales of $993 million in 2004, reports Dr. Joel Finkelstein, an osteoporosis researcher at Massachusetts General Hospital in Boston.

Calcium supplements, Finkelstein wrote in an editorial in the New England Journal of Medicine, are "the biggest seller of the multibillion-dollar dietary-supplement industry."

Those messages may have falsely reassured many women that the supplements are going to protect them, Finkelstein said.


Supplement with a combination tablet providing a 2/1 to 1/1 ratio of calcium to magnesium.

Calcium carbonate is absorbed well by most people, but calcium citrate is recommended for those with digestive problems..

Vitamin D,  magnesium, boron,  zinc, trace minerals, vitamin C and adequate protein are also important for bone health..

Dark green vegetables, nuts, legumes are rich in both calcium and magnesium.

Milk, cheese and yogurt are rich in calcium but relatively low in magnesium.

Weight-bearing exercise is good for bones.

Caffeine, alcohol, smoking and excess salt leech calcium out of bones. Reduce or avoid consumption.

P-I reporter Susan Phinney contributed to this report.

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