What nutritional deficiency causes splitting nails and toenails?

I have noticed my toenails cracking in the center as they grow outWhat nutritional deficiency causes splitting nails and toenails?
this can be caused by a number of things. vitamin b defficiency, nail fungus or a damaged nail bed. if it is the last thing then your nails will always crack as they grow out.What nutritional deficiency causes splitting nails and toenails?
iron
lack of folic acid biotin...amino acids...msm calcium and vitamin d
lack of minerals
While it could be nutritional deficiency (usually lack of calcium, iron, or protein is to blame if this is the case), it can also be nail fungus, injuries to the nails (stubbed your toes lately?), or even the soap or skin products you may use. Also, your nails can do weird things of the matrix is damaged; for example, I had a finger that was once sliced all the way through near the tip (there's a scar under my nail from it), and now that nail always grows crooked, so it's reasonable that nails could also split depending on what kind of damage the matrix may have received.
Deficiencies in minerals, mostly, affect nail health:





cacium


iodine


silica


zinc