Parents should ensure that their children and teens get enough calcium and weight-bearing exercise to help them reach their maximum bone density. 1 Dietary Reference Intakes for Calcium, Phosphorus, Magnesium, Vitamin D, and Fluoride, The National Academy of Sciences, 1997. 2 NIH Consensus Conference Statement on Optimal Calcium Intake, 1994. 3 Recommended Dietary Allowances, National Research Council, 1989. Bioavailability is the degree to which the intestinal system can absorb calcium.
Absorption depends on the overall level of calcium in the food and the type of food being consumed.
Foods vary in their ability to enhance or inhibit calcium absorption. The efficiency of calcium absorption is fairly similar for foods such as dairy products and grains. Oxalates in particular are strong inhibitors of calcium absorption. As a result, additional servings of many calcium-rich foods are needed to compensate for their low calcium absorption. According to the National Academy of Sciences report on the new DRIs, the body absorbs about a tenth as much calcium from spinach as it does from milk.