The Canadian Cancer Society is so impressed with the growing evidence (see Ed) that vitamin D reduces the risk of a wide variety of cancers that is has issued a formal recommendation:

• Adults living in Canada should take 1,000 international units (iu) of vitamin D3 a day during the autumn and winter months
• Adults at higher risk of having lower vitamin D3 levels should take 1,000iu of vitamin D3 a day all year round, e.g.
  
  • people who are older
  • people with dark skin
  • people who don’t go outside often
  • people who wear clothing that covers most of their skin

View Vitamin Research Products' vitamin D3 1,000iu supplement

It explained that Canada’s northerly latitude made it particularly difficult for citizens to get enough vitamin D3 from the sun during autumn and winter.

At this time, the Canadian Cancer Society has not formulated a recommendation for children. Research to date on the role of
vitamin D3 and cancer prevention has focused on adults.

The Canadian Dermatology Association has also recently upped its recommendation for vitamin D3 - to 1,000iu a day all year round.

Ed.- A recent meta-analysis concluded that consuming 1,000iu a day may prevent a half of all human cancers. Adequate doses (2,000 units per day) may prevent even more cancers. [1]