手指甲跟钙没什么直接的关系。

很多人认为钙是指甲的主要成分。因此缺钙会造成指甲开裂，或失去光泽。其实不然。指甲的主要成分是角蛋白，钙的含量在0.03%。请看《新英格兰医学》的一篇文章和CNN的一个报道。

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 ..."