Winter has arrived across much of India, and with it comes a quiet health problem that affects most of us. We live in one of the sunniest countries in the world, yet a large share of Indians walk around low on vitamin D. Shorter days, a lower sun and smoggy winter skies make it harder for the body to make the vitamin it needs.
The numbers are striking. A large analysis by Metropolis Healthcare of more than 2.2 million vitamin D tests done across India between 2019 and January 2025 found that 46.5 per cent of people tested were deficient, and another 26 per cent had insufficient levels. A senior Mumbai physician writing in The Times of India this month put the wider figure even higher, saying more than 70 per cent of Indians across age groups are vitamin D deficient.
Why winter sun is not enough on its own
Your skin makes vitamin D when UVB rays from sunlight fall on it. In winter, the sun sits lower in the sky, days are shorter, and the UVB that reaches your skin is weaker. The Indian Express reported this week that winter sunlight may not provide enough UVB to maintain vitamin D, and that afternoon exposure may need to go on for over an hour to help.
Three everyday habits quietly make things worse. First, window glass blocks UVB completely, so sitting beside a sunny window does not help at all. Second, smog filters out UVB, and winter is pollution season in much of north India. A 2021 study in Communications Earth and Environment found that particulate matter can cut UV radiation by up to 60 per cent in polluted cities. Third, most of us spend the brightest hours indoors, at a desk or in a classroom, and step out only in the early morning or evening, when the sun is too low to make much vitamin D.
The right way to take winter sun
Experts broadly agree on the window: late morning to early afternoon, roughly 10 am to 3 pm, is when UVB is strongest in Indian winters. Aim for 20 to 30 minutes of direct sun on bare arms and face, a few days a week. People with darker skin may need a little longer, since melanin slows vitamin D production.
A few practical rules make the habit stick:
- Step out after lunch for a short terrace or balcony break, instead of staying at your desk.
- Walk to the market or take a midday stroll rather than driving for short errands.
- Keep it short and frequent. Short, regular exposure beats one long weekend session, and you should never burn your skin chasing vitamin D.
- Do not rely on sunlight through glass. Step outside, even if it is only for a few minutes.
Morning light still matters, just for a different reason. Even through a window, early light helps set your body clock and improves sleep. Morning light wakes you up; midday light makes vitamin D.
What to eat when the sun falls short
Very few foods are naturally rich in vitamin D, and most of them are non-vegetarian, so food alone rarely closes the gap. Fatty fish such as sardine and mackerel, egg yolks, mushrooms exposed to sunlight, and fortified milk and cereals all help. A glass of fortified milk carries roughly 40 to 60 IU, so look for the FSSAI plus-F logo on the pack.
For most vegetarians, food alone will not reach the daily requirement. The ICMR-NIN Nutrient Requirements for Indians (2020) puts the adult requirement at about 600 IU a day. Sunlight remains the main source, and a doctor may suggest a supplement after a test.
Should you get tested?
If you have aching knees, a stiff back, frequent tiredness or low mood in winter, a test is worth discussing with your doctor. The correct test is a 25(OH)D blood test. Levels below 20 ng per ml are commonly considered deficient, 20 to 30 is insufficient, and 30 to 100 is sufficient. No fasting is needed, and levels move slowly, so retesting is usually done after 8 to 12 weeks, not every month.
Supplements can correct low levels, but the dose should come from a doctor, not a guess. High-dose courses are meant to catch up levels, and a lower maintenance dose follows. Taking large doses without testing can lead to too much vitamin D, which carries its own health risks.
FAQs
Is early morning sun good for vitamin D?
Not really. The sun is too low in the sky in the early morning to produce much UVB. Midday sun, between about 10 am and 3 pm, is far more effective.
How much sun do I need in winter?
About 20 to 30 minutes of direct midday sun on bare arms and face, a few days a week. People with darker skin may need longer.
Can I get vitamin D through a window?
No. Window glass blocks UVB rays, so sitting in sunlight indoors does not produce vitamin D.
Which foods have vitamin D?
Fatty fish, egg yolks, UV-exposed mushrooms and fortified milk and cereals. Food alone usually cannot meet the full daily need of about 600 IU.
When should I get tested?
Ask your doctor for a 25(OH)D test if you have bone aches, fatigue or low mood, or if you spend most of your day indoors. Test before starting a high-dose supplement.
