I'm not a doctor, but I am a mom who has tried all those "healthy nail" pills and products in an effort to improve the state of my weak, peeling nails. In all my trials, I finally came across a great ingredient that actually works: jojoba oil. My nails have never been better!
The key for me was to put the oil on my hands and nails before bed, and to rub it into my cuticles. The healthier (meaning less dry) my cuticles were, the healthier my nail beds and nails became. This has become a nightly routine for me, and even without the vitamins, my nails are strong, healthy and pretty!