Date of Award:

1974

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Nutrition, Dietetics, and Food Sciences

Department name when degree awarded

Nutrition and Food Sciences

Advisor/Chair:

Arthur W. Mahoney

Abstract

Dietary calcium has been classified as one of the minerals frequently limiting in the American diet (FAO, 1962) . Bone demineralization has been observed as a result of calcium deficient diets (Salomon et al., 1972), partial gastrectomies (Eddy, 1971) and inadequate hormonal balance (Albright et al., 1948). Although bone demineralization, or osteoporosis, has been attributed to many factors, the interrelationship of gastric acidity and the utilization of dietary calcium may be a key to the etiology of osteoporosis.

Eighty weanling male albino rats were divided into eight groups. All animals had their stomachs exposed through a mid-line incision. Control rats were sham-operated while the treatment animals had their stomachs X-irradiated to destroy the secretory cells. Four diets were prepared containing calcium carbonate, calcium chloride, tri-calcium phosphate or calcium gluconate as calcium sources. For a three-week experimental period, ten control and ten X-irradiated rats were fed each diet.

In vitro data suggests that the solubility of each calcium salt, except calcium gluconate, increased in an acid media. Saturated viii ix solutions of calcium carbonate and tri-calcium phosphate had low quantities of calcium ion in solution in neutral pH's, but as the acidity was changed from pH 4 to pH 3 the calcium ion concentration increased as much as eight times. This demonstrates that the presence of acid with insoluble forms of calcium salts will generally increase calcium ion concentration in solution.

All X-irradiated animals had an average fasting gastric pH of over 6, while the control rats averaged pH 2.5. The calcium absorption data demonstrates that X-irradiated rats fed diets containing soluble calcium salts (calcium chloride, 18.5 percent and calcium gluconate, 25.13 percent) had increased absorption values over those fed diets containing calcium salts of low solubility (calcium carbonate, 12.94 percent and tri-calcium phosphate, -7.06 percent).

Femur strength and bone calcium data reflected similar evidence. Both femur strength and bone calcium of the X-irradiated rats fed the less soluble forms of calcium salt were significantly lower than the controls, while X-irradiated rats fed the more soluble forms of calcium had femur strength and bone calcium similar to the controls.

Achlorhydric, or X-irradiated, animals were observed to have decreased iron stores in comparison with the control rats. Hemoglobin levels, liver iron and iron absorption were all significantly reduced in the x-irradiated animals.

From the results of these experiments, it is apparent that gastric acidity and the solubility of the dietary calcium source play an important role in the utilization of calcium.

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