Vitamin D deficiency is often associated with older adults, but studies increasingly highlight low vitamin D levels among adolescents and young adults.
In India, the problem is particularly striking because the country receives substantial sunlight for much of the year.
A recent study of 1,009 Indian adolescent girls aged 11–18 found that 50% were vitamin D deficient, while another 37.9% had insufficient levels.
Researchers identified inadequate dietary vitamin D intake and socioeconomic factors as important contributors.
Research among younger Indians has also pointed to the role of lifestyle.
A study using data from the Comprehensive National Nutrition Survey found vitamin D deficiency among 23.9% of Indian adolescents aged 10–19.
Urban residence, vegetarian diets, lower physical activity, and other demographic factors were among the factors associated with deficiency.
So, why does deficiency occur despite all the sunshine?
One major reason is that sunlight only helps when the skin is exposed to UVB radiation. Spending most of the day indoors at school, college, work or home can reduce that exposure.
Pollution, clothing that covers much of the skin, and darker skin pigmentation can also affect vitamin D production.
Diet is another part of the problem. Naturally occurring vitamin D is found in relatively few foods, including fatty fish and egg yolks, while fortified foods can provide an additional source.
A 2024 study based on more than 11,000 vitamin D tests at a North-West Indian tertiary-care centre found that people in the 21–30 age group had the lowest median vitamin D level among the age groups studied.
Overall, 60% of those tested were classified as deficient under the study’s criteria.
Vitamin D is important for calcium absorption and bone health, while also playing roles in muscle and immune function. Severe deficiency can cause bone pain and muscle weakness in adolescents and adults.
However, experts caution against assuming that every unexplained symptom is caused by vitamin D deficiency or taking high-dose supplements without medical advice.
Blood testing can determine vitamin D status, while excessive supplementation can itself cause toxicity and dangerously high calcium levels.
For young people, the issue may therefore be less about a lack of sunshine and more about how modern routines have changed the way they interact with it — long hours indoors, limited physical activity and diets that may not provide enough vitamin D.