How does vitamin C affect bones and bone loss?
What are the current recommended amounts to maintain bone health in adults?

Vitamin C (ascorbic acid) plays 2 roles in bone health.
It is essential for the synthesis of collagen, the major protein component of bone.
Scorbutic animals show bone loss, and infants with scurvy present with rickets with deformation of the rib cage. Second, vitamin C is an antioxidant, able to scavenge free radicals. In the process of bone resorption, free radicals are formed that, if unchecked, can decrease bone formation and lead to loss of BMD

Current Recommended Dietary Allowance (RDA) values for vitamin C for adults — 90 mg for men and 75 mg for women — were set to provide antioxidant protection and are higher than amounts needed to prevent scurvy. The typical Canadian diet meets these requirements, provided sufficient fruits and vegetables are consumed. On average, Canadian men and women obtain 118 mg and 102 mg, respectively, from food sources alone. Intake of vitamin C supplements is common, and can range from 50 mg to 1000 mg. An Upper Level of 2000 mg was set, as higher intakes can cause osmotic diarrhea

Reference: Osteoporosis Update (Cannada), Summer 2009. Volume 13 No.2