White spots in the fingernails or toenails are associated with a need for essential trace mineral zinc.  People can have normal looking nails and still require more zinc, however.

Zinc is one of the most common nutrient deficiencies in older people, especially those in nursing homes.  Many of these people need zinc but don’t have the white spots in the nails.  But if the white spots are present, supplementing the diet with 15 mg. of zinc, once or twice a day is a good idea.

Ridges (horizontal or vertical) in the fingernails are often an indication of a need for the essential trace minerals iron and/or molybdenum.  People who need molybdenum are often sensitive to perfumes or other odors.  Consider supplementing the diet with 100 mcg of molybdenum three times a day (300 mcg. total per day.)

It takes months for the ridges to grow out and disappear.  If they return after stopping the molybdenum supplement, it suggests that there is an ongoing need for supplementation.