Sunlight is the most expensive drug that could be taken free of cost.
Skin pigmentation (melanin) shields against UV- B rays hence dark skinned individuals need longer sunlight exposure to activate Vit D production.
For individuals with dark skin (such as Asian Indians) a minimum 30 minutes of exposure of the skin to sunlight, preferably between 10am to 2pm twice a week is advised.
During this time the ultraviolet B radiation (wavelength 290-315 nm) is the highest. The UV- B rays penetrate the skin and convert 7-dehydrocholesterol to Vit D.
For those with light skin (such as Europeans), a 15 minute of exposure to sunlight is recommended.
Foods rich in Vit D are fishes like Salmon, Sardines, Tuna etc.
Cod liver oil is also a good source.
Nowadys milk, juices, yogurt and butter are also spiced with Vit D.
Studies comparing Vit D levels between Indian immigrants and Europeans living in Western countries with less sunlight indicate that Vit D is much lower in the Indians. It is advisable that Indians living in colder regions may consume Vit D supplements particularly during the winter time (Nov and April).