Nutrient intake and Urine and Serum Calcium Response to a low Calcium Diet and Repletion

A high percentage of American women do not consume the Recommended Dietary Allowance for calcium. Marginal intake of calcium (Ca) in the years when peak bone mass is being formed may have a detrimental impact on bone later in life. This study looked at the effect of low Ca intake and other dietary components on serum and urine values of Ca as well as the response to repletion. Seventeen free-living females, age 21 to 30 years, were placed on a low Ca diet (/day) for 22 days after a baseline of intake \u3e800 mg/day for at least 6 weeks. Calcibind was given throughout the low Ca period to decrease Ca availability. Phosphorus intake was kept constant with Neutra-Phos-K supplementation. Seven days of repletion at \u3e800 mg/day followed the low Ca diet. Blood and urine samples were collected 7 times. During the low Ca period energy, protein, and Ca intakes were significantly different from baseline and repletion. Sodium intake was significantly different only from baseline. Mean serum Ca concentration significantly lower than baseline on days 2 and 3 of the low Ca diet. By day 22 on the diet, serum Ca had returned to baseline and remained unchanged throughout repletion. Urinary Ca values were significantly reduced during the low Ca diet and rapidly returned to baseline values during repletion. A significant decrease in Ca intake resulted in significant reduction of several dietary components as well as urine and serum Ca levels, but healthy, young females adapted rapidly to repletion on a high Ca intake