Experts at AIIMS-Delhi have advised people to maintain vitamin D levels in their body in view of high air pollution in the city that is blocking out most of sunlight, a potent source of the nutrient.

People of all age groups can consider taking supplements during winters as per the advice of their doctors and this can be done even without checking vitamin D levels if the supplementation is moderate such as 60,000 IU of cholecalciferol, said Dr Ravinder Goswami, professor in the Department of Endocrinology and Metabolism at AIIMS.

Active vitamin D analogues and injectables should be avoided because of the risk of toxicity, he said.

"One should not take active analogues such as calcitriol as these are meant for therapeutic use in kidney diseases. Cholecalciferol is good and most economical. It automatically gets converted into active form in the body in a controlled manner in the required amount without causing toxicity. Unnecessary consumption of supplements may lead to heart problems," he said.

He said that a study by the department has shown normal vitamin D status in Delhiites working outdoors.

"Assessment of vitamin D status among outdoor workers such as hawkers or street vendors, fuel stations attendants, manual auto rickshaw pullers, traffic police personnel and gardeners were found to be vitamin D sufficient with level nearing 20 nanogram per ml just by proper sun exposure from 10 am to 2 pm without any supplementation," Dr Goswami said.

However, those working indoors were found to be vitamin D deficient unless they are taking supplements, he added.

The prevalence of vitamin D deficiency can vary from negligible in outdoor workers to as much as 60-80 per cent in indoor workers, Dr Goswami said.

Currently, 20 nanogram per ml of vitamin D is considered sufficient for all age groups, he underlined.

Dr Soma Saha, a researcher in the Department of Endocrinology and Metabolism at AIIMS, said that the absence of vitamin D deficiency (VDD) in the construction workers was explained by compulsory long hours of sun exposure.

"However, the study suggested a likelihood of good vitamin D status among people working outdoors under sun with freedom to seek shade off and on as per their need," she said.

It is important to assess the vitamin D status of people working outdoors in order to focus on strategies for tackling VDD in cities, Dr Saha said, adding that vitamin D supplementation should be offered to indoor workers only with VDD.

"Contrary to the popular perception, VDD is not universal in urban population and the majority of outdoor workers achieve vitamin D sufficiency by just following their day-to-day schedule. It is important to adopt a conservative view on fortification of food with vitamin D in countries with ample of sunshine due to the possibility of hypercalcemia and renal stone," Dr Goswami said.

Explaining who all are predisposed to VDD in India, Dr Saha said that those who stay indoors as office and bench workers, patients with kidney disorders, gastrointestinal disorders, TB and epilepsy are predisposed.

"Vitamin D is required for the synthesis of calcium transporters in the gut luminal cells. It, therefore, helps absorb dietary calcium in the gut. The serum calcium along with phosphorus mineralizes the bone," Dr Saha stated.

If the vitamin D levels are chronically low, it may lead to short stature, bone pain, muscle ache, limping gait, and rickets with bow legs, the experts said.

"In pregnancy, it may lead to low birthweight and in old age, it may lead to osteoporosis, hunch back, vertebral fractures, bone pain. Loss of height in adulthood is a clinical clue of osteoporosis as vertebral fractures reduce spinal length," Dr Saha said.

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