The vitamin is particularly beneficial for people with breast cancer, bowel cancer and lymphoma.
The nutrient is made by the body under the skin in reaction to summer sunlight and found in oily fish, such as salmon, sardines and mackerel, eggs and fortified fat spreads, breakfast cereals and powdered milk.
It helps the body absorb the calcium and phosphorus needed for healthy bones and affects a variety of biological processes by binding to a protein called a vitamin D receptor.
This receptor is present in nearly every cell in the body.
A new study found cancer patients who have higher levels of vitamin D when they are diagnosed tend to have better survival rates and remain in remission longer than patients who are vitamin D deficient.
Scientists reviewed all previous research to acknowledge the health benefits of the vitamin.