some facts from wikipedia
Light-exposed mushrooms may provide up to 100% of the recommended Daily Value of vitamin D.[4]
Vitamin D also modulates neuromuscular function, reduces inflammation, and influences the action of many genes that regulate the proliferation, differentiation and apoptosis of cells
Vitamin D is a group of fat-soluble secosteroids, the two major physiologically relevant forms of which are vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol).
prevention of hypocalcemic tetany
while sufficiency prevents rickets in children and osteomalacia in adults
The usual cause of tetany is lack of calcium, but excess of phosphate (high phosphate-to-calcium ratio) can also trigger the spasms. Milk-and-alkali tetany is an example of this imbalance.
Underfunction of the parathyroid gland can lead to tetany.
Low levels of carbon dioxide cause tetany by altering the albumin binding of calcium such that the ionised (physiologically influencing) fraction of calcium is reduced; the most common reason for low carbon dioxide levels is hyperventilation.
Low levels of magnesium can also lead to tetany symptoms.
Rebirthing-Breathwork, purposeful rapid breathing for one - two hours at a time; first causing hyperventilation, can sometimes lead to tetany.
Cow grazing on rapidly grown pasture with tetany of the neck suggesting Grass TetanyAn excess of potassium in grass hay or pasture can trigger winter tetany or grass tetany, respectively, in ruminants.
Osteomalacia in children is known as rickets
nerve disease
The most common cause of the disease is a deficiency in vitamin D,
some of this stuff you can find on migraine sites ,or here o2 magnesium rickets is said to be painfull
steroids etc ,