Vitamin A from beta carotene

Niacin from tryptophan

First, due to the inability of our bodies to manufacture the compound, enough of the compound must be consumed in the diet to maintain health.

Second, symptoms of deficiency occur with the absence of the compound, resulting in declining health.

preformed Vitamin A (retinol/retinal)  Retinal helps eye adjust from bright to dim light.  Without it we can get night blindness.  We can also get xeropthalmia if deficient which is drying out of the eye.

provitamin A carotenoids precursors from plants, includes beta carotene.  Many are antioxidants.

Also helps with epithelial cells (GI tract), growth, development, reproduction, immunity.  Found in liver, fish, fish oil, orange and yellow fruits.  Toxicity can result in hip fracture, liver toxicity, fetal malformations

Should get 3000 micrograms a day

is a hormone.  forms include ergocalciferol, synthetic D2, and cholecalciferol made in the human body.

Skin cells contain cholesterol converted in sun, converted in liver, converted in kidney to active form

Sources, fatty fish, fortified cereal, eggs, butter, fortified milk

works in conjunction with parathyroid hormone to absorb calcium and phosphorus from intestine and deposit in calcium in the bones.  

also important for immune system, skin development, muscle health, and blood pressure control

deficiency, rickets, osteomalacia, osteoporosis