ST. LOUIS -- Women who got most of their calcium from food had higher bone-mineral densities than patients who relied on supplements, researchers here reported.
ST LOUIS, June 20 -- Women who got most of their calcium from food had higher bone-mineral densities than patients who relied on supplements, researchers here reported.
Surprisingly, the finding of better bone density at the spine and hip for the milk and cheese eaters held even though women taking supplements had a higher calcium intake, said Reina Armamento-Villareal, M.D., of Washington University, and colleagues, in the May issue of the American Journal of Clinical Nutrition.
In addition, women getting most of their calcium from food had more estrogen metabolites, a shift in the estrogen hydroxylation pathway, which may produce a positive bone-mineral homeostasis and greater bone density, the researcher said.
The results came from a study of 183 postmenopausal white women who were divided into three groups. Thirty-three women who took supplements got at least 70% of their daily calcium from tablets or pills.
Seventy women got at least 70% of their daily calcium from dairy products and other foods.
A diet-plus-supplement group consisted of 65 women whose calcium-source percentages fell somewhere between these ranges.
In addition, the researchers tested urinary concentrations of estrogen metabolites.
The women relying on dietary calcium (primarily dairy sources) took in the least calcium (mean 830 mg/d) yet had higher spine and hip bone-density scores than those relying on supplements who consumed 1,033 mg/d.
Women in the diet-plus-supplement group with the highest calcium intake at 1,620 mg/d tended to have the highest bone mineral density, the researchers reported.
Compared with women taking supplements, adjusted bone mineral density z scores were significantly greater in the women who obtained calcium primarily from food or from both diet and supplements (at the spine, P = 0.012, femoral neck, P = 0.02, total femur P = 0.003, and intertrochanter, P =0.005).
This difference was evident especially in those who obtained calcium primarily from their diet, yet whose total calcium intake was lower than that of the supplement-takers, the researchers said.
Women who obtained calcium primarily from food or from both food and supplements also had significantly (P = 0.03) lower ratios of nonestrogenic to estrogenic metabolites (2-hydroxyestrone 1/16 ?-hydroxyestrone) than did the women taking supplements, the researchers reported.
This finding, they said, corroborates their earlier report suggesting that calcium may be an important modulator of estrogen hydroxylation favoring the production of active estrogen metabolites.
In contrast, it is possible that nutrients other than calcium, present in calcium-rich foods, cause this shift in estrogen metabolism.
Alternatively, they said, dietary sources of calcium may also contain active estrogenic compounds that can influence bone density and the amount of estrogenic metabolites in the urine.
Another possible explanation, they pointed out is better bioavailability of dietary calcium compared with supplemental calcium.
Calcium salts are available in many over-the-counter supplements, they said, but their solubility and bioavailability are highly variable and may be affected by the presence of other compounds in the supplements or by when the pills are taken.
For example, some supplements must be taken at a meal so that stomach acids can facilitate absorption.
Finally, the researchers said that it is likely that the better bone mineral density in women getting their calcium from food may have resulted from a lifelong healthier diet.
Thus the investigators in this study found that women who consumed a significant amount of calcium from dietary sources, on average, consumed more servings of fruit and fruit juices per week than did the women who consumed calcium primarily from supplements. Also, significantly fewer women who consumed calcium from dietary sources were past smokers.
The study's limitations included its cross-sectional design, which may not have reflected lifelong calcium intakes. In addition, only one seven-day dietary record was used to assess the women's dietary habits.
These results suggest that the type of calcium may be an important determinant in estrogen metabolism and the consumption of dietary calcium should be encouraged in patients at risk of bone loss, the researchers concluded.