Natural medicine practitioners have been asking this question for years. You may have heard about the updated Public Health England guidelines extending recommendations for Vitamin D3. https://www.gov.uk/government/news/phe-publishes-new-advice-on-vitamin-d
Basically, as an adult take a daily supplement containing 10mcg of vitamin D throughout the year if you:
- are not often outdoors, such as those who are frail or housebound
- are in an institution such as a care home (work in an office? added by me)
- usually wear clothes that cover up most of their skin when outdoors
- have dark skin, such as those of African, African-Caribbean or South Asian origin
As usual, the devil is in the detail. Latest research shows that maximum absorption is by way of oil/spray/liposomal form rather than a powder pill and adding Vitamin K2 MK-7 in key and it also takes care of the calcium issue.
Quick reference to UK the guidelines .