I have very weak thin nails that peel and split. Is there anything that works to strengthen them - are the nutrients that help?

I've used certain nail hardener products myself. You'll find them in the same general area as the nail polishes/products in most stores that sell such things. Usually works for me. Not sure about supplements/nutrients though, I don't know anything about that.

I have that same problem and I applied nutra nail about twice a day for the past three days and it has done wonders for my brittle nails.

Fragile Nails with horizontal or vertical ridges. Probable cause: Vitamin B deficiency. A lack of the B vitamin causes nail to become fragile, with horizontal or vertical ridges appearing. Horizontal ridges can also be a signal of a hormonal imbalance and sometimes appear during menstruation. . Nails are strengthened by supplemental use of vitamins like the biotin along with the other B complex vitamins, they must be taken in combination with an amino acid complex and the vitamins C and E, these will help the body manufacture keratin and other proteins that strengthen nails in a synergistic manner-all these supplements act together in maintaining strong nails and must be used in combination. Nail growth is also aided by the presence of an essential mineral sulfur, in fact nail growth cannot proceed with a deficiency of this mineral as it is an essential constituent of keratin.

Nails also gain benefit from ingesting a bone building combination formula which is rich in calcium and other minerals-these minerals strengthen the bone at the same time. Nails are also prevented from cracking and are better nourished by consuming the oil of the flaxseed along with the evening primrose oil; these essential herbal oils are very rich in two different types of essential fatty acids considered necessary for proper nail strength and growth.

Vertical ridges may signal anemia or iron deficiency or may results from aging or dryness.

Iron and zinc deficiency. White spots on the nails can be cause by a zinc deficiency.

There are other minerals for weak nails but I can't remember what they are.
Will try to add when I think of them.