[PHNUTR-L] Dietary calcium is better than supplements at protecting bone health

[Kathrynne Holden]

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Public release date: 19-Jun-2007
http://www.eurekalert.org/pub_releases/2007-06/wuso-dci061907.php

Contact: Gwen Ericson
ericsong at wustl.edu
314-286-0141
Washington University School of Medicine

Dietary calcium is better than supplements at protecting bone health

Women who get most of their daily calcium from food have healthier bones 
than women whose calcium comes mainly from supplemental tablets, say 
researchers at Washington University School of Medicine in St. Louis. 
Surprisingly, this is true even though the supplement takers have higher 
average calcium intake.

Adequate calcium is important to prevent osteoporosis, which affects an 
estimated 8 million American women and 2 million American men. Another 
34 million Americans have low bone mass, placing them at increased risk 
for osteoporosis. Calcium consumption can help maintain bone density by 
preventing the body from stealing the calcium it needs from the bones.

The researchers' conclusions about calcium intake, published in the May 
issue of the American Journal of Clinical Nutrition, came from a study 
of 183 postmenopausal women. The researchers asked the women to 
meticulously detail their diet and their calcium supplement intake for a 
week. "We assumed that this sample represented each woman's typical 
diet," says senior author Reina Armamento-Villareal, M.D., assistant 
professor of medicine in the Division of Bone and Mineral Diseases and a 
bone specialist at Barnes-Jewish Hospital. "In addition to analyzing the 
volunteers' daily calcium intake, we tested bone mineral density and 
urinary concentrations of estrogen metabolites."

The researchers found that the women could be divided into three groups: 
one group, called the "supplement group," got at least 70 percent of 
their daily calcium from tablets or pills; another, the "diet group," 
got at least 70 percent of their calcium from dairy products and other 
foods; and a third, the "diet plus supplement group," consisted of those 
whose calcium-source percentages fell somewhere in between these ranges.

The "diet group" took in the least calcium, an average of 830 milligrams 
per day. Yet this group had higher bone density in their spines and 
hipbones than women in the "supplement group," who consumed about 1,030 
milligrams per day. Women in the "diet plus supplement group" tended to 
have the highest bone mineral density as well as the highest calcium 
intake at 1,620 milligrams per day.

The hormone estrogen is known to maintain bone mineral density. But the 
standard form of estrogen is broken down or metabolized in the liver to 
other forms - some active and some inactive. Urinalysis showed that 
women in the "diet group" and the "diet plus supplement group" had a 
higher ratio of active to inactive estrogen metabolites than women in 
the "supplement group."

"This suggests that dietary calcium is associated with a shift in 
estrogen metabolism that favors production of active forms of estrogen," 
says Armamento-Villareal. "Although we're not yet certain what underlies 
this effect, it could be that nutrients other than calcium cause this 
shift. It's also known that dairy products, which are a major source of 
calcium, can contain active estrogenic compounds, and these can 
influence bone density and the amount of estrogenic metabolites in the 
urine."

Calcium supplements differ in how well their calcium can be absorbed, 
and this also could play a role in the study's findings, according to 
its authors. For example, calcium carbonate tablets need to be taken 
with a meal so that stomach acid can facilitate absorption, but calcium 
citrate tablets don't have this limitation. If the study participants 
taking calcium carbonate weren't conscientious about the timing of their 
supplements, they might not have received the highest benefit from them.

"Only about 35 percent of the calcium in most supplements ends up being 
absorbed by the body," Armamento-Villareal says. "Calcium from the diet 
is generally better absorbed, and this could be another reason that 
women who got a high percentage of calcium in their food had higher bone 
densities."

Although dairy foods are excellent sources of calcium, 
Armamento-Villareal suggests that individuals with dairy sensitivities 
could consume other calcium-rich food sources such as calcium-fortified 
orange juice. Dark green leafy vegetables also contain calcium, but it 
is not as readily absorbed as calcium from dairy sources.
###

Napoli N, Thompson J, Civitelli R, Armamento-Villareal RC. Effects of 
dietary calcium compared with calcium supplements on estrogen metabolism 
and bone mineral density. American Journal of Clinical Nutrition 
2007;85:1428-1433.

Funding from the National Institutes of Health and the General Clinical 
Research Center at Washington University supported this research.
-- 
Kathrynne Holden, MS, RD < fivestar at nutritionucanlivewith.com >
"Ask the Parkinson Dietitian"  http://www.parkinson.org/
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