The dry winter air, from having the heater on, can make it hard to stay moisturized in the colder months. You need to drink more water and pay attention to replacing the moisture on your hands after you wash them. This is really important when you use sanitizing hand gels. They contain alcohol which is potentially drying to the skin and the nails. Use cuticle oil, found in the nail polish section , and apply it to the nail AND the skin around the nail whenever you can.
Your diet also is important. If nails are brittle and fragile, Salem, OR-based Elizabeth Somer, RD, author of Age-Proof Your Body (McGraw-Hill, 2006), recommends consuming iron-rich foods such as black bean soup or the occasional cut of steak. "Iron is essential for the growth and maintenance of the nails and nail bed," says Somer. "If nails are deprived of iron for too long, they can flatten out or curve abnormally." Somer adds that cooking foods in a cast-iron pan can also help increase your iron intake. The iron from the pan infuses into whatever dish you're preparing. I hope this information helps you have long and strong nails this winter!