Vitamin D is also known as the sunshine vitamin, Vitamin D is both a nutrient we eat and a hormone our bodies make. It is a fat-soluble vitamin that has long been known to help the body absorb and retain calcium and phosphorus; both are critical for building bone.
Few foods naturally contain vitamin D, though some foods are fortified with the vitamin.
For most people, the best way to get enough vitamin D is taking a supplement because it is hard to eat
enough through food.
Vitamin D supplements are available in two forms:
(1) vitamin D2 (“ergocalciferol” or pre-vitamin D) (2) vitamin D3 (“cholecalciferol”).
Both are also naturally occurring forms that are produced in the presence of
the sun’s ultraviolet-B (UVB) rays, hence its nickname, “the sunshine vitamin,
but D2 is produced in plants and fungi and D3 in animals, including humans.
Vitamin D production in the skin is the primary natural source of vitamin D, But many people have insufficient levels because they live in places where sunlight is limited in winter, or because they have limited sun exposure due to being inside much of the time.
Also, people with darker skin tend to have lower blood levels of vitamin D because the pigment (melanin) acts like a shade.
It reduces production of vitamin D (and also reducing damaging effects of sunlight on skin, including skin cancer).
WHAT VITAMIN D PROMOTES IN THE BODY
Vitamin D promotes calcium absorption in the gut and maintains adequate serum calcium and phosphate concentrations to enable normal bone mineralization . It prevents involuntary contraction of muscles, leading to cramps and spasms.
It is also needed for bone growth and bone remodeling by osteoblasts and osteoclasts . Without sufficient vitamin D, bones can become thin, brittle, or misshapen.
Vitamin D sufficiency prevents rickets in children and osteomalacia in adults. Together with calcium, vitamin D also helps protect older adults from osteoporosis.