**6. Sunlight for vitamin D replacement**

Most people meet at least some of their vitamin D needs through exposure to sunlight [28]. Solar ultraviolet B radiation crosses the skin and converts 7-dehydrocholesterol to previtamin D3, which is rapidly converted to vitamin D3. Excessive sunlight exposure does not cause intoxication because any excess previtamin D3 or vitamin D3 is destroyed by sunlight, and in the skin there is reversible conversion to inactive sterols [24].

In residential aged care, practical attempts for therapeutic sunlight therapy have produced only mild 25(OH)D3 improvements and depended on the season of exposure [29]. On a practical level, excessive exposure to ultraviolet is the primary cause of skin cancer, including squamous cell carcinoma, basal cell carcinoma and cutaneous malignant melanoma [30], so this is not a pragmatic approach from a public health perspective. Essentially, people with limited sun exposure require good dietary sources of vitamin D or take a supplement to achieve recommended intake levels.

Besides increasing sun exposure, the best way to get additional vitamin D is through supplementation.
