While in any bone stress or stress fracture injury we must first consider bio-mechanical and technical factors, in dancers who experience frequent injuries, or are slow to heal from a simple injury, it would be wise to consider the possibility of a Vitamin D deficiency as a contributing factor.
In countries with high sunshine hours, you would expect there to be no issues with Vitamin D levels, however, possibly due to promotions such as the “Slip-Slop-Slap” rule, introduced in the 1980’s in both New Zealand and Australia to reduce the incidence of skin Cancers and Melanoma, many young people are not getting adequate sunlight to allow the production of Vitamin D naturally. This is especially relevant for young athletes who train a lot indoors (Ballet, Gymnastics etc).
In some countries, staple foods such as milk, flour and margarine are artificially fortified with vitamin D, and it is also available as a supplement in pill form. Food sources such as fatty fish, eggs, and meat are rich in vitamin D and are often recommended for consumption to those suffering vitamin D deficiency, however it is much harder to gain the quantities of Vitamin needed to protect bones from food sources than it is from sunlight.