Habitual calcium intake and vitamin D status during adulthood through estrogen deficiency have few interactions on calcium kinetics and bone

Abstract

Eating patterns do not change as rapidly as the physiological changes that accompany the menopause. As such, habitual nutrition status may strongly affect post menopausal bone health in the general population. To test how dietary calcium (Ca) and vitamin D (VD) interact to influence bone during the menopause, we studied 70 female Sprague Dawley rats from young adulthood through ovariectomy (OVX)‐induced estrogen deficiency. Weanling rats were housed in a UV‐free environment and fed an AIN93G diet with 0.4% Ca and 100 IU VD/kg diet for 5 weeks. At 8 weeks of age, rats were randomized to AIN93M diets containing 0.2 or 1.0% Ca and 50, 100, or 1000 IU VD/kg diet. OVX was performed at 12 weeks of age. At 24–28 weeks of age, Ca kinetics was performed with a 45Ca tracer (oral Ca dose: 15 mg) up to 48 hours. Kinetics was modeled using WinSAAM software. A Ca and VD interaction was seen in the soft tissue compartment, but each nutrient independently increased endogenous Ca secretion. Bone formation was not affected by either nutrient. However, rats on the 1% Ca diet had lower fractional Ca absorption, higher net Ca absorption and higher bone balance due to reduced bone resorption, regardless of VD intake. Habitual Ca intake and VD status during adulthood throughout estrogen deficiency have few interactions on Ca kinetics and bone. Rather, Ca intake may be more influential to benefit bone than VD status at levels relevant to the general population.