Seeing we live in a country where the sunshine seem to be limited to the summer time if we are lucky enough to have proper summer conditions, or can afford the ticket for each family member too go abroad throughout the year, it’s recommended that we top up orally with this vitamin, throughout the autumn and winter months of the year since vitamin D levels in the blood naturally tend to fall.
Vitamin D, Can only be produced in our bodies by the action of direct sunlight on the skin, many experts even consider it more of a prohormone than a vitamin .
1- Vitamin D must be metabolized to it biologically active form in the body, after it is consumed or synthesized in the skin, it then enters the bloodstream for transport to the liver, there it is hydroxylated to form 25 hydroxyvitamin D. In the kidney, a second hydroxylation results in calciferol, or 1.25 dihydroxyvitamin – THE MOST POTENT FORM. In animal, this forms cholecalciferol, or vitamin D3. In plant, this forms ergocalciferol or vitamin D2.
2- Lack of vitamin D, due to poor diet and little sun exposure, reduce bone mineralization, this can lead to the deficiency diseases of ricket in children, and ostemalacia adults, Bone thining 0steoporosis in menopausal women is partly regulated by the amount of vitamin D obtained in the diet or from supplement. When vitamin D is in short supply, less calcium is absorbed from the diet and blood levels therefore have to be maintained by leaching calcium from bones. 4 out of 5 people with hip fracture have evidence of vitamin D deficiency.
Vitamin D deficiency play a role in case such as cancer, heart disease, osteoporosis, osteoarthritis, the common cold, asthma, brain function, skin texture and appearance, bacterial vaginosis and many more area of the body.
3- Dietary source rich in vitamin D: Egg yolk, oily fish such as mackerel, sardines, salmon, fortified food with vitamin d, also to note vitamin D is the only vitamin that can be obtained via the sun.
4- Supplement dosage very depending on where or how the information is gathered, some research indicate as low as 200IU up to 2500IU daily, the best way to know what your individual level is by doing your own blood test to see what levels you currently are, if that not in your budget you can supplement with Vitamin D supplement made from the D3 version (cholecalciferol) as it appears to be 20-40 per cent more effective in maintaining blood vitamin D levels than D2 (ergocalciferol form).
(extracted from The essential of sport and exercise nutrition by precision nutrition, course manual pg 179,chapter 7 unit 1, and the essential guide to vitamins, mineral and herbal supplement by Sarah Brewer)