Vitamin D plays main role in maintaining calcium levels in various organs of body specially bone and blood. Vitamin D is required for absorption of calcium from intestines and deposition in bone. It also acts on parathyroid gland for control of parathyroid hormone secretion.
Deficiency of vitamin D in growing children results in deformities of lower limbs. These are either bow legs or knock knees, a condition known as rickets. After the growth period is over, deficiency results in pseudo-fractures and bone pains, a condition known as osteomalacia.
Mounting evidence suggests that vitamin D deficiency could be linked to several chronic diseases, including cardiovascular (heart) diseases and cancer (1).
Vitamin D deficiency is a highly prevalent condition in any countries around the globe. It is associated with most cardiovascular diseases (CVD) risk factors and with CVD morbidity and mortality (2).
Epidemiological studies suggest that deficiency of vitamin D increases the incidence of colon cancer and also has a negative impact on the survival of colon cancer patients (3)
There is evidence that vitamin D is involved in our defence against respiratory tract infections (4). Research is going on find out the benefits of adequate vitamin D levels in the body for building immunity against COVID-19.
Variants of vitamin D: All variants of vitamin-D are cholesterol related substances and are fat soluble.
Cholecalciferol is a naturally occurring compound in animal products and fish oils
Ergocalciferol is the synthetic compound available in fortified food products.
Both these variants are changed in liver and kidneys to become activated. The activated vitamin D is known as calcitriol (Vitamin D3). This process of activation is adversely affected in old age and in few diseases of liver and kidneys. In such conditions, active forms of vitamin D are required.
Fatty fish, such as herring, salmon, tuna and sardines
Meat products, beef and liver
Butter, eggs and fortified foods such as margarine and milk
Sunlight is yet another and very important natural source to increase vitamin D. Ultraviolet-B (UVB) rays of sunlight act on skin cells to change cholesterol into vitamin D. In temperate zones where sunlight is intense, early morning exposure for about 30 minutes daily is sufficient. In cold climates, mid day exposure will be required to have good result. Dark skinned people need more exposure.
It is worth noting that vitamin D content of animal products is dependent upon the individual animal’s vitamin D status. Therefore if the animal has vitamin-D deficiency, its products will have much less quantity of this vitamin. There is a concern that animal and fish farming has resulted in decline in vitamin D of these animals. One study has shown about 75% decrease in vitamin D content of farmed as compared to wild salmon.
Summary: Vitamin D plays important role in calcium metabolism of body. It has been found to reduce risks of heart diseases and cancer of large intestine. Vitamin D also boosts body immunity against many respiratory disorders and may have role in COVID-19 patients.