People who have more vitamin D in their blood are less likely to develop bowel cancer than those with low levels, researchers claim.
According to a study published in the British Medical Journal, those with the highest levels of the vitamin were at 40 per cent lower risk of developing the disease compared with those with the lowest levels.
Scientists looked at vitamin D quantities in 1,248 people with bowel cancer and 1,248 controls in the largest ever study of the subject.
The research was carried out by scientists at the International Agency for Research on Cancer (IARC) in Lyon, France, and Imperial College London, and was funded by World Cancer Research Fund (WCRF).
It comes after medical experts expressed concern yesterday 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.
According to the research team, 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 WCRF, 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.
“Looking at the figures in this latest study, it suggests that increasing the UK’s vitamin D intake by 10% could prevent 7% of cases.
“And when you think that there are about 37,500 cases diagnosed in the UK every year, that could have a big impact.
“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.”
Dr Mazda Jenab, the lead author of the study from the International Agency for Research on Cancer, said: “Our results support a role for vitamin D in the etiology of colorectal cancer, but this has to be balanced with caution regarding the potential toxic effects of too much vitamin D and the fact that very little is known about the association of vitamin D with either increased or reduced risk of other cancers.”