Thank you for your post enquiring about optimal sunlight exposure for vitamin D production for people with osteoporosis. I’m aware that there is a thread on this subject in the general forum, with a link to the National Osteoporosis Society’s webpage showing the Joint position statement on vitamin D (December 2010). http://www.nos.org.uk/Page.aspx?pid=311#16122010anchor.  The key messages however are listed below. It goes without saying that these are just recommendations and a guide to what to aim for in terms of sunlight exposure. Clearly it will need to be adapted to each individual’s situation (for example skin type). To answer your question about recommendations for people with osteoporosis, having extra sunlight exposure over and above the general recommendation, is unlikely to confer any additional benefit for bone health.
 
‘Vitamin D helps the body use calcium and is essential for healthy bones
Sunlight is the best natural source of Vitamin D
Exposure to sunlight every day between May and September will increase Vitamin D levels.
Your body stores vitamin D for the winter months.
You should try to get 10 minutes of sun exposure to your bare skin, once or twice a day (depending on skin type) without sunscreen and taking care not to burn. On cloudy days, it can take a little longer. Always take care not to burn, especially during the strong sunshine in the middle of the day.  Babies and children have very sensitive skin and need careful protection. Those with fair or sensitive skin need to be careful not to redden or burn their skin and will need to restrict exposure
Make sure you are outside – glass prevents the ultra violet rays reaching your skin.
Pregnant women; those who don’t get sunlight exposure; older frailer people; those on antiepileptic drugs may need vitamin D supplements.   A daily dose of 10 - 20 micrograms (400-800 IU) is usually sufficient.’

Best wishes

Helpline Nurses
National Osteoporosis Society