Food Matters

Vitamin D and Colorectal Cancer

Previous studies have indicated an association between vitamin D and colorectal cancer, but the evidence has been inconclusive. A recent study led collaboratively by the International Agency for Research on Cancer (IARC, Lyon, France) and Imperial College London (London, UK) and funded by the World Cancer Research Fund (WCRF) has examined the association between pre-diagnostic circulating vitamin D concentrations, dietary intake of vitamin D and calcium and the risk of colorectal cancer in European populations.

The study (published in the British Medical Journal ) states that the primary role of vitamin D is to maintain calcium balance in the body and bone metabolism. It is thought that vitamin D may play a part in cancer control by modulating cellular growth and cell death and by reducing angiogenesis (the growth of new blood vessels from pre-existing vessels). Active hormones from the main circulating 25-hydroxy-vitamin D, can be produced in normal and neoplastic colon cells which indicates that it may control the growth of these cells, although the evidence on this is inconclusive. Dietary factors such as calcium, retinal and alcohol may influence vitamin D metabolism, although these have not been well studied.

The researchers used data from the European Prospective Investigation into Cancer and Nutrition (EPIC), a prospective cohort of more than 520,000 people from 10 Western European countries, aimed at investigating the associations between blood vitamin D concentrations and colorectal cancer risk. Dietary and lifestyle questionnaires and blood samples were collected between 1992 and 1998. Using a combination of methods, the participants were tracked for several years for cancer incidences. Colorectal cancer is the combination of colon and rectal cancer cases. During tracking there were 1,248 colorectal cancers diagnosed and these were matched to 1,248 healthy controls.

The study found that participants with the highest levels of blood vitamin D concentration had a nearly 40% decrease in colorectal cancer risk compared to those with the lowest levels of vitamin D. Previous studies have indicated that vitamin D levels at 50nmol/l or more can prevent colorectal cancer. The researchers then compared low and high levels of blood vitamin D concentration to a mid-level of 50-75 nmol/l. They found that levels of blood vitamin D lower than 50nmol/l were associated with an increased risk of colorectal cancer. However, levels higher than 75nmol/l were associated with a reduced risk, although this was not significant compared to the mid range concentration. The study also states that higher consumption of dietary calcium but not dietary vitamin D was found to be associated with a reduced risk of colorectal cancer particularly in the rectal anatomical sub site.

The study concluded by stating that although the results indicated a role for vitamin D in the prevention of colorectal cancer there was little known about the association of vitamin D and other cancers and the long term health effects of very high circulating vitamin D concentrations. The authors suggested that new randomised trials needed to be done to test whether increasing circulating vitamin D is effective in reducing colorectal cancer risk and that it does not cause any serious health risks.

(From RSSL Food e-news Edition 473: 20-27 January 2010)

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