Answer: Biotin or vitamin B7
Step-by-step explanation:
Biotin or Vitamin B7 is a crucial in keeping the nails and hair healthy. This element helps in the strengthening the weak and brittle nails and hair.
As we known the nails and hair are made of protein, L-lysine supplements cab be taken to keep the hair and nails healthy.
The diet of the person should be rich in protein and vitamin B7. So, a person who is having poor nails must have a diet rich in proteins.