Three hours a day cut the risk of developing breast cancer by half, reveals research.
It is the latest in a series of studies that add to the already strong evidence that the 'sunshine vitamin' helps prevent cancer.
The researchers at the University of Toronto found that being outdoors stimulates the production of the vitamin and exposure to sunlight for 21 hours a week between April and October significantly cuts the chances of developing a tumour, reports the Daily Star.
Although we get some vitamin D from foods such as fatty fish, milk and eggs, around 90 percent is generated in the skin by ultraviolet light from the sun.
Laboratory tests suggest that breast cells are capable of converting vitamin D to a hormone that has anti-cancer properties.
To measure how sun exposure affected the development of cancer, the researchers compared 3,101 breast cancer victims with 3,471 healthy women who had not suffered tumours.
Each one was questioned on how much time they spent outdoors from spring to autumn during four stages of life from their teens to the age of 74.
The results showed that women who had at least 21 hours a week exposure to the sun's UV rays in their teens were 29 percent less likely to get cancer than those getting under an hour a day.
By the time they reached their 20s and 30s, the risks dropped by 36 percent. By the time women had reached 60, sunshine had halved their chances of a tumour.
The results are published in the American Journal of Epidemiology. (ANI)