What causes ridges in your nails, they grow across the nail from the cutical to the tip?

I remember from school this being a missing nutriant (SP) but I cant remember what it is. Any Dietitians out there?What causes ridges in your nails, they grow across the nail from the cutical to the tip?
A vitamin B deficiency causes horizontal and vertical ridges in the nail. Also, low iron may cause concave or ';spoon'; nails and/or vertical ridges.What causes ridges in your nails, they grow across the nail from the cutical to the tip?
Vertical nail ridges, which run from the cuticle to the tip of the nail, are fairly common. They don't indicate serious illness and typically increase with age. Although their exact cause isn't known, heredity may play a role. If your fingernails change color or develop horizontal ridges, see your doctor. These changes may indicate an underlying health problem.