How do toenails grow?
Just as our eyes do, nails can tell a doctor a lot about the
overall health of their patient. Curved nails are caused by: *
Insufficient Vitamin B12 * It can indicate Cardiopulmonary disease
or asthma * It MAY indicate heart, liver or arsenic poisoning It is
probably insufficient Vitamin B12. If you are letting your nails
grow very long they also can sometimes grow under or even twist if
they are super long.