http://content.nejm.org/cgi/content/extract/343/24/1817
There is a widespread belief among the general public that dietary calcium intake improves the quality of fingernails and toenails. Persons taking calcium supplements sometimes comment that their nails are less brittle or smoother, or that they grow faster. Presumably, the idea that dietary calcium improves nails has arisen because nails contain calcium, albeit at a much lower concentration (0.03 percent)1 than the skeleton (20 to 25 percent).
http://archives.cnn.com/2000/HEALTH/...eut/index.html
"...the belief that calcium helps nail growth is widespread, presumably because nails contain calcium, the element that keeps bones strong. However, bones have 800 times more calcium than nails.
The new results "provide no support for the idea that calcium intake alters self-reported nail quality ..."