Direct sunlight is a great source of vitamin D.

Sunlight and vitamin D requirements

If you live in the tropics and can expose your unprotected skin to two sessions of 15 minutes of sunlight each week your body will naturally produce adequate amounts of vitamin D.

Direct sunlight is a great source of vitamin D. However, be careful you do not overdo it.
 

The following factors may reduce your body's vitamin D synthesis:

• If you live far from the equator, your sunlight exposure will be less during many months of the year.
• Cloud cover
• Smog
• Sunscreens

If your body cannot produce enough vitamin D because of insufficient sunlight exposure you will need to obtain it from supplements and dietary sources.

In the absence of sun exposure 1000 IU of cholecalciferol is required daily for both children and adults, according to a study by Boston University School of Medicine.

People with dark skin pigmentation and the elderly are more likely to have vitamin D deficiencies.

Vitamin D levels in females in winter - women with arthritis, diabetes and some other chronic conditions are much more susceptible to reductions in vitamin D levels during the winter months, researchers from Vanderbilt University Medical Center in Nashville, Tenn., reported at the 2012 American Society of Clinical Pathology Annual Meeting.

They added that doctors should become aware of this and help these patients maintain adequate levels of vitamin D during the winter season.

Recent developments on vitamin D and sunlight from MNT news
 
Vitamin D deficiency a risk factor for African-American men living in poor sunlight areas. Researchers at Northwestern University Feinberg School of Medicine found that African-American men living in low sunlight areas are at a higher risk of vitamin D deficiency than European-American men living in the same areas.