How Much Sunlight?

Our richest source of vitamin D is from the UVB rays of the sun, but there are many factors that affect the amount of vitamin D we manufacture from the sun.


UV rays are most intense at the equator but at higher latitudes further from the equator, the sun is lower in the sky and travels through more ozone to reach earth, making UV radiation less intense

Time of day

At midday when the sun is at its highest point, UV radiation has a shorter distance to travel. In early morning or late afternoon, the UV rays are at an oblique angle and the intensity is less

Time of year

The angle of the sun varies by season and sunlight is the most intense in summer


The UV radiation is more intense at higher altitudes as there is less atmosphere to absorb it


Cloudy conditions reduce the penetration of UV rays


Less UV radiation reaches the earth as air pollution can filter it out


Surfaces such as snow, sand and water can intensify UV rays


Wearing sunscreen prevents the body from making vitamin D. SPF 15 reduces it by 95% and SPF 30 by almost 99%

Skin colour

The darker your skin, the more sun you need as the melanin that gives skin its colour acts as a natural sunscreen. Darker skin may require up to six times more sun exposure to produce the same amount of vitamin D as lighter skin.

Source: The Vitamin D Solution – Dr. M. F. Holick, Australian Edition 2000

View the OsteVit-D range