White spots on the nail can be due to zinc deficiency. Nothing what a daily dose of zinc supplement cannot solve. However, I would advise you to seek an opinion from your doctor. It may be harmless and all that but a medical opinion is always the best opinion. Your doctor will even tell you which is the right supplement to have.
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While there are many reasons for these white spots (called leukonychia), most of them are due to mild trauma -- such as hitting or slamming your fingernail on or into something -- and there's usually little cause for worry. The good news is they'll simply be out with time.
Certain nutritional deficiencies, particularly a lack of zinc or protein in your diet, can cause a nearly total whiteout of your nail except for the tips or even a pattern of white bands across the width of the nail. Cirrhosis, a form of chronic liver disease usually brought about by alcoholism, can also result in nails that are almost completely white. Keep in mind, though, that white spots in that case are rarely the primary flag for diagnosis but usually occur well after this disease has made its presence known in other ways.