This research indicates that Vitamin D, not calcium, may be a greater factor in improving bone strength and reducing the risk of stress fractures in children. The Institute of Medicine has recently increased the recommended dietary allowance for vitamin D for teenagers to 600 international units (IU) daily. Good sources of Vitamin D include salmon, cod liver oil, egg yolk, organ meats (e.g., liver) and possibly mushrooms (although its bio-availability hasn’t been proven). So, just another reason to include cod liver oil in your diet! Read more here.