Vitamin D is unusual among nutrients: your skin makes it when exposed to sunlight, yet deficiency is surprisingly common, even in sunny countries. Surveys in India and many other regions show that large portions of the population have low blood levels. Here is what you need to know.
What Does Vitamin D Do?
- Helps your gut absorb calcium and phosphorus for strong bones and teeth
- Supports muscle function and balance
- Plays a role in immune system regulation
- Contributes to normal cell growth
Severe deficiency causes rickets in children and osteomalacia (soft bones) in adults, and long-term low levels contribute to osteoporosis.
How Much Vitamin D Do You Need?
| Group | Typical recommended intake |
|---|---|
| Infants 0 to 12 months | 400 IU (10 mcg) |
| Children and adults 1 to 70 years | 600 IU (15 mcg) |
| Adults over 70 | 800 IU (20 mcg) |
| Upper safe limit for adults | 4,000 IU (100 mcg) |
Some national guidelines differ slightly, and a doctor may recommend higher doses to correct a diagnosed deficiency.
Sunlight: The Main Source
When UVB rays hit bare skin, your body converts a cholesterol compound into vitamin D3. Short, regular exposure of the face, arms and legs, often around 10 to 30 minutes several times a week at midday, is enough for many people with lighter skin. People with darker skin, those who cover most of their body, older adults, people living at higher latitudes in winter, and those who work indoors make less and may need dietary sources or supplements. Sunscreen is important for skin cancer prevention, so balance sensible sun exposure with sun safety.
Best Food Sources of Vitamin D
- Fatty fish: Salmon, sardines, mackerel and herring are among the richest natural sources, with a serving often providing 400 to 800 IU or more.
- Cod liver oil: Very high, so use only as directed.
- Egg yolks: About 40 IU each, varying with the hen’s diet.
- UV-exposed mushrooms: Mushrooms exposed to UV light can supply meaningful amounts of vitamin D2.
- Fortified foods: Milk, some plant milks, cereals, orange juice and fats may be fortified. Check the label.
Signs of Low Vitamin D
Many people have no obvious symptoms. When symptoms occur they can include bone or back pain, muscle weakness, frequent fatigue, low mood and slow fracture healing. These are non-specific, so only a blood test (25-hydroxyvitamin D) can confirm a deficiency.
Should You Take a Supplement?
Supplements are useful for people with limited sun exposure, certain medical conditions or confirmed low levels. Vitamin D3 (cholecalciferol) is generally more effective at raising blood levels than D2. Taking it with a meal containing fat improves absorption. Very high doses over long periods can cause calcium build-up, so avoid self-prescribing large amounts and discuss testing and dosing with your doctor.
Tips to Get Enough Vitamin D
- Get short, safe midday sun exposure several days a week.
- Eat oily fish twice a week if you eat fish.
- Include eggs and UV-exposed mushrooms.
- Choose fortified foods where available.
- Ask your doctor about testing if you are at risk.
Frequently Asked Questions
Can I get vitamin D through a window?
Glass blocks most UVB rays, so sitting by a window does not produce much vitamin D.
Is vitamin D enough for strong bones on its own?
No. You also need adequate calcium, protein, magnesium and weight-bearing exercise.
The Bottom Line
Combine smart sun exposure, vitamin D-rich foods and, where needed, a doctor-guided supplement to maintain healthy levels for lifelong bone and muscle health.
This article is for general education and is not a substitute for personalised advice from a registered dietitian or doctor.