Blocked UV rays cause Vitamin D deficiency

a study carried out in Delhi has added another dimension to the effect of vehicular pollution on human health. Researchers have found that haze caused by pollutants can significantly reduce ultraviolet (uv-b) rays available to synthesise vitamin d. Levels of the vitamin in the blood of children living in a more polluted area were found to be less than half as compared to kids living in a less polluted area.

The study was conducted by various organisations, including Delhi-based Saint Stephen's hospital. The researchers attribute the problem to high pollution levels that reduce the amount of ultraviolet (uv-b) rays reaching Earth. The skin uses uv-b rays to synthesise vitamin d from its precursor form. With reduced amounts of uv-b available for conversion, less vitamin d is formed. This affects the body's calcium uptake from food, as the vitamin is essential for this. As a result, children suffer from diseases like rickets that is characterised by bones getting weak. Moreover, the deficiency also leads to parathormone hormone leaching out calcium from the bones to maintain calcium levels in the blood.

The researchers conducted the study on 26 children living in highly polluted Mori Gate area and on 31 kids of relatively less polluted Gurgaon. They measured the amount of vitamin d in blood samples. uv-b levels in both areas were also taken into consideration.

The researchers found that more uv-b was reaching the ground in Gurgaon than Mori Gate. Blood sample analysis showed that all 26 children living in the Mori gate area had a significantly lower level of vitamin d in their blood. Moreover, three children had levels low enough to be associated with rickets. Another nine had concentrations below level regarded as the lower limit for vitamin d adequacy. Compared to this, none of the 31 children from Gurgaon area showed vitamin d deficiency.

The study questions the belief that since India receives abundant sunlight, children here are not likely to suffer from vitamin d deficiency. "Because of their dark skin which cuts off the entry of uv-b in skin, more sunlight is needed by Indians,' says Puliyel. However, the researchers reiterate that further study needs to be conducted to delve the matter adequately.