Why do Indians need Vitamin D supplements? Low sunlight, pollution and indoor living to blame

Thirty five-year-old Manish came to me complaining of muscle pains and excessive fatigue. He had a desk job with an IT company. He was a regular exerciser, yet the muscle pains would not go away. A friend then suggested testing for vitamin D (25OHD) level, which was found to be 8 ng/ml, much lower than the recommended level of 20 ng/ml. I prescribed him vitamin D supplements. In six weeks, his pains had all but disappeared, and he was back to his peak performance at work.
Why is vitamin D important for us?
Calcium is the principal constituent of our bones. Vitamin D is crucial for absorption of calcium. In the absence of vitamin D, calcium does not get absorbed into our blood from our gut and thus does not reach our bones. Low vitamin D also impacts muscles. Vitamin D is made in our skin under the influence of UV rays of the sun. Subsequently it undergoes activation in the liver and then kidney. Very little vitamin D is available through diet sources, unless food is fortified with vitamin D.
What happens if we are deficient?
Severe D deficiency (levels typically below 10 ng/ml) can lead to weak bones, even fractures, and profound weakness that can result in the affected individual being wheelchair-bound. In growing children, this can result in bone deformities, typically bowing of the legs, called rickets. Serious deficiency has become less common now, although there has been a rise in such cases due to indoor confinement in the pandemic. Moderate deficiency producing body aches, muscle pains and fatigue continues to be quite common in urban India. Low-grade, asymptomatic deficiency can pers for long periods, resulting in poor calcium absorption, and contributing to bone damage that can potentially manifest with low bone density and fractures in older age.

In addition to musculoskeletal effects, vitamin D may also play an important role in other body processes. In particular, Vitamin D deficiency has been shown to increase the risk of respiratory infections, including COVID-19. It is, therefore, logical to keep our D levels in the optimum range.
Why is vitamin D deficiency common in India?
Vitamin D deficiency is widely prevalent in India, particularly in the urban areas. This deficiency is seen across all ages, from new-borns to the elderly, and includes pregnant women. Depending on the cut-off used and the population studied, the prevalence of vitamin D deficiency varies from 17 to 90 per cent across India. Deficiency is more prevalent in cities than villages, and more in the North than in the South, which is closer to the equator. As recently as 2020, our data showed that as many as 25 per cent patients hospitalised with Covid had levels below 10 ng/ml!
An important reason for this deficiency is that many urban Indians spent almost all their time indoors, with hardly any sunlight exposure. When they do go out, they are well covered. Some may use sunscreen which also blocks vitamin D synthesis. To add to our woes, air pollution is at its peak during this (winter) season and prevents the right kind of UV rays from reaching our skin and further lowers vitamin D levels, which are in any case lower in winter.

What should we do?
In general, it is important for all Indians to increase their sunlight exposure. For those living in polluted cities, it makes sense to supplement with 1000-2000 IU of vitamin D daily, particularly during winter months, although up to 4000 IU/day is quite safe for most adults. People who are indoor-confined, newborns and elderly groups, are particularly vulnerable. Adolescents and pregnant women are also groups where maintaining vitamin D level is particularly important. Use of lower daily doses is preferred over large intermittent doses. Injectable vitamin D contains very high amounts (600,000 IU) and is not recommended. We have reported many cases of vitamin D toxicity due to grossly excessive doses being used.
For those with symptoms or who just want to be sure, measurement of 25OHD level is possible with the dose then being tailored their doctor. However, even in the absence of a test, use of low daily doses is safe.
At the level of public health, severity of Vitamin D deficiency can be attenuated mass fortification of food products, as is the practice in many countries. Vitamin D fortification of popular and commonly consumed commodities such as milk and edible oil, as recommended FSSAI, is an established approach. Severe D deficiency has been virtually eradicated in North America and Europe because of widespread fortification of food products, in particular, dairy products. However, a recent study showed that the FSSAI-recommended average daily intake of vitamin D through fortified milk and oil (240 IU) may not be sufficient to raise the serum levels of vitamin D to the normal range. Still, it is a vital step in the right direction and should logically lead to mandatory fortification, and ultimately a revision of the amount of vitamin D to be added.
Encouragingly, in 2020 the Government issued a gazette notification with guidelines and standards for edible oil and milk fortification with Vitamins A and D. While fortification is not a panacea for the epidemic of vitamin D deficiency, it is a logical and established approach to reduce the severity of deficiency.
The time to act is NOW.
(The author is a Padma Bhushan recipient)