People who have more vitamin D in their blood are less likely to develop bowel cancer than those with low levels, researchers said on Friday.
According to a study published in the British Medical Journal, those with the highest levels of the vitamin were at 40% lower risk of developing the disease compared with those with the lowest levels.
It comes after medical experts expressed concern on Thursday about the rising number of cases of rickets - caused by vitamin D deficiency - and called for it to be added to milk and other food products.
The main source of vitamin D is sunlight, through skin exposure, but it is also present in a small number of foods, such as oily fish or cod liver oil.
The research team said that although the latest study provides evidence of a link between vitamin D and bowel cancer, it does not prove that taking vitamin D supplements prevents the disease.
More studies are needed to find out the potential impact on other cancers and the effects of taking extra vitamin D doses, scientists said.
Dr Panagiota Mitrou, science programme manager for the World Cancer Research Fund, said: "This is the biggest ever study on this subject and there is now quite a lot of evidence from studying populations that people who have low levels of vitamin D are more likely to develop bowel cancer.
"The next step is to carry out new clinical trials to try to confirm whether vitamin D supplementation can reduce the risk of bowel cancer and whether there are any harmful effects of higher levels of vitamin D.
"But we need to emphasise that, for the moment, the findings need to be treated with caution and they are certainly not enough evidence to suggest that we should be taking supplements to increase levels of vitamin D.
"The best advice for reducing risk of bowel cancer remains to stop smoking, maintain a healthy weight, be regularly physically active, to eat more fibre and less red and processed meats and to cut down on alcohol."