Vitamin D and your health

Vitamin D, also known as sunshine vitamin refers to a group of fat soluble secosteroids. It can be produced in the body with mild sun exposure or consumed in food or supplements. In humans, the most important compounds in this group are vitamin D3 (cholecalciferol) and vitamin D2 (ergocalciferol) which can be ingested from the diet and from supplement.
Although the body has the ability to make vitamin D, there are many reasons deficiency occurs. Darker skin pigments and sunscreen use can significantly decrease the body’s ability to absorb UV rays required to produce vitamin D. The skin has to be directly exposed to sunlight not covering with cloth. It is estimated that sensible sun exposure on bare skin for 5-10mins 2-3times per week allows the body to produce sufficient vitamin D.
Adequate intake is responsible for enhancing intestinal absorption of zinc, calcium, iron, magnesium and phosphorus.
Vitamin D is also responsible for the maintenance of healthy bones and teeth. Vitamin D deficiency in children can cause rickets (a disease characterized by a severely bow-legged appearance triggered by impaired mineralization and softening of the bones). In adults, deficiency manifest as osteoporosis (most common bone disease among post-menopausal women and older men) or osteomalacia (which results in poor bone density, muscular weakness and often causes small pseudo fractures of the spine and femur).
Vitamin D is suggested to supply a protective effect against multiple diseases and conditions such as diabetes, cancer, tuberculosis, multiple sclerosis etc. Insufficient vitamin D level may have an adverse effects on insulin secretion and glucose intolerance. Vitamin D  is extremely important for regulating cell growth. Hormonally active form of vitamin D, calcitrol, can reduce cancer progression by slowing the growth and development of new blood vessels in cancerous tissue and increasing cancer cell death. Low level of vitamin D appears to be a risk factor for tuberculosis. Deficiency has also been linked to increased risk of viral infections, including influenza and HIV.
Pregnant women who are deficient in vitamin D seems to be at greater risk of developing preeclampsia and needing a cesarean section, also associated with gestational diabetes mellitus and bacterial vaginosis. High level of vitamin D during pregnancy were associated with increase in food allergy of the child during the first 2 years of life. Infants who are exclusively breastfed are also at high risk of vitamin D deficiency, especially if they are dark-skinned or have minimal sun exposure. Pregnant and breastfeeding women should consult their physician before taking a vitamin D supplement.
Excessive consumption of vitamin D, hypervitaminosis D, can lead to the over calcification of bone and hardening of blood vessels, kidney, heart and lungs. Most common symptoms are headache, dry mouth, loss of appetite, nausea and vomiting etc.
Food sources of vitamin D are cod liver oil, egg, chicken, tuna, sardines and salmon.
Recommended intake:
0-50 years- 5mcg/200iu per day
51-70 years- 10mcg/400iu per day
71 and above-15mcg/600iu per day (1mcg=40iu)
Exclusively breastfed infants- 400iu per day of an oral vitamin D supplement.
Upper level limit for infants (birth-12months)- 25mcg/day (1000iu)
Upper level limit for adult- 4000iu/day
First focus on obtaining your daily vitamin D requirement from sunlight and foods, then use supplements as a backup.
It is the overall eating pattern that is most important in disease prevention and achieving good health. It is better to eat a diet with variety than to concentrate on one individual nutrient as the key to good health.