In the winter, especially, nails become brittle, rough, ridged and seem to peel. Does this mean I have a vitamin deficiency? What should we do to solve this problem?
Diets often change during the winter,and marginal deficiencies may show up. Insufficient protein seems to be high on the list,though the often-recommended use of gelatin does not seem to be adequate. However, I find that improving the digestion overall is the best single thing that can be done.
Consider a really good supplement of digestive enzymes, like Super Enzyme, by Twinlab, or something equivalent (read labels). Try one right after every meal (not before), and go to two if there's no problem (it's rare that there would be).
Eat slowly, chew thoroughly, and add high-protein foods like fish, meat, and especially whole eggs, which are high in sulfur amino acids. Cholesterol is almost never a problem as long as you don't break the yolk during cooking.
Keep your hands in good condition from the very beginning, and you will not have any problem with them in future!