Learning outcomes:
By the end of this activity you should know:
- UV radiation is a natural source for the initiation of the production of vitamin D
- moderate exposure to solar UV radiation of an adequate area of skin produces an adequate amount of vitamin D for everyday health
- how to estimate the exposure times to obtain the recommended UV dose for optimal vitamin D levels.
One of the health benefits of exposure to UV radiation is the production of vitamin D, which is important for good overall health, in particular for strong and healthy bones and muscles. Although vitamin D can also be obtained from some foods and vitamin tablets, the simplest and cheapest way to obtain vitamin D is from moderate exposure to solar UV radiation.
The daily exposure time required for an exposure dose that produces sufficient vitamin D levels depends mainly on the environmental conditions and individual genetic factors. In general, people with highly pigmented skin would require exposures 3-4 times greater than those required for fair-skinned people to produce adequate vitamin D levels. Also, older adults require longer exposure times as the efficiency of producing vitamin D decreases with age.
Current Australian guidelines suggest that exposure of 15% of the skin (an area of skin equivalent to face, arms and hands) of a fair-skinned person to about 1/6 – 1/3 of a minimum erythemal dose (MED) would be appropriate to achieve adequate vitamin D production.
The following presented real data shows that a couple of minutes of solar UV exposure either side of the middle part of a summer day provides the 1/6 MED required for vitamin D production. The presentation also shows that longer times are required to accumulate 1/6 MED during other parts of the day.
Questions
- Why is a longer exposure time required in the morning to produce adequate vitamin D?
- Starting from 10:00 and exposing 45% of the skin, use the provided data to estimate the exposure time for a fair-skinned adult required to produce adequate vitamin D.
- Do the clouds prevent us from producing vitamin D? Investigate the period 10:00-11:00 and note the effect of clouds.