The 2005 Dietary Guidelines for Americans also recommends milk and milk products as sources of dietary calcium based on studies that show a positive relationship between intake of milk and milk products and bone mineral content or bone mineral density at one or more skeletal sites.
The NICHD has selected low-fat or fat-free milk as an excellent source of calcium because it has high calcium content without added fat, and because the calcium is easily absorbed by the body. Low-fat and fat-free milk products are also good sources of calcium.
Other foods, including dark green, leafy vegetables such as kale, are also healthy dietary sources of calcium. But, it takes 11 to 14 servings of kale to get the same amount of calcium in 3 or 4 8-ounce glasses of milk.
In addition to calcium, milk provides other essential nutrients that are important for optimal bone health and development, including:
How does bioavailability affect calcium absorption?
Bioavailability, the degree to which the intestinal system absorbs calcium, depends on the overall level of calcium in a food and the type of food being consumed. Calcium in foods such as milk and milk products is highly bioavailable.
According to the National Academy of Sciences' 1997 report on Dietary Reference Intakes, the body absorbs about one-tenth as much calcium from spinach as it does from milk. High bioavailability is one of the reasons that the NICHD describes milk and milk products as excellent dietary sources of calcium.
Children and teenagers should have low-fat or fat-free milk and milk products. Because these items contain little or no fat, it's easy to get enough calcium without adding extra fat to the diet.
Most types of milk have approximately 300 mg of calcium per 8 fluid ounces (1 cup) - about 25 percent of the calcium that children and teenagers need every day.
Low-fat or fat-free milk is best for tweens and teens.
Children one to two years old should drink whole milk. After age two, low-fat or fat-free milk should become their regular drink. (Source: Dietary Guidelines for Americans, 2005)
Are there any special calcium recommendations for pregnant or lactating teens?
Increasing dietary calcium does not prevent the loss of calcium that occurs during lactation, and the calcium lost seems to be regained after weaning. Therefore, the Dietary Reference Intakes do not recommend increasing calcium intake for lactating adolescents above normal levels for their age group.
Although calcium is found in a variety of foods, the 
