I live in the north west where we don't get much sun. how do i know if i should be supplementing vitamin d, and is a vitamin d supplement the best way to combat the lack of sun exposure? vitamin supplements

Fatty fish is best: There's a possible role of vitamin D against cancer, heart disease, fractures & cognitive functioning. The flesh of fatty fish such as salmon, tuna, and mackerel are among the "best sources". The recommended daily amount of vit D is 400 IU for children up to age 12 months, 600 IU for ages 1 to 70 years & 800 IU for people over 70 years. Taking too much vit D can be very harmful! I wish you well!