There are no studies about whether supplementing with vitamin D will help prevent dementia or improve the condition because testing is expensive and pharmaceutical companies cannot make large profits.
Studies have shown that individuals with higher levels of vitamin D were 59% less likely to get dementia. Vitamin D can also help prevent fractures and bone loss.

Campbell said that UK national health guidelines advise minute doses of vitamin D at 10 micrograms (400 international units) of vitamin D a day. He says that he takes ten times that amount (100 micrograms or 4000 iu). He recommended sunlight that can produce 20,000 units of vitamin D per day without burning.