Vitamin D may improve colorectal cancer survival
People with the highest average levels of 25-hydroxyvitamin D (25-(OH)D) – the non-active storage form of the vitamin – had a cancer-specific mortality half that of people with the lowest average levels, says a new study published in the British Journal of Cancer.
Furthermore, high levels of the vitamin were associated with an overall mortality level 40 per cent lower than people with the lowest average levels, state the Boston-based researchers led by Prof Kimmie Ng, from the Dana-Farber Cancer Institute.
“Higher predicted 25(OH)D levels after a diagnosis of colorectal cancer may be associated with improved survival,” stated the researchers. However, they noted that additional research is needed in order to elucidate the mechanism by which vitamin D may improve survival rates.
The link between vitamin D intake and protection from cancer dates from the 1940s when Frank Apperly demonstrated a link between latitude and deaths from cancer, and suggested that sunlight gave "a relative cancer immunity".
A meta-analysis published in the American Journal of Preventive Medicine reported in 2007 that higher blood levels of 25(OH)D were associated with a lower risk of colon cancer.
"Through this meta-analysis we found that raising the serum level of 25-hydroxyvitamin D to 34 ng/ml would reduce the incidence rates of colorectal cancer by half," said lead author Edward Gorham from the University of California.
The new study analysed data from 1,017 participants in the Nurses' Health Study and Health Professionals Follow-Up Study previously diagnosed with colorectal cancer. It appears to add to the potential vitamin D benefits for colorectal health by indicating that higher levels may also improve survival rates amongst people already living with the disease.
There are 363,000 new cases of colorectal cancer every year in Europe, with an estimated 945,000 globally. There are about 492,000 deaths from the cancer each year. Only about five per cent of colorectal adenomas are thought to become malignant, and this process could take between five and ten years.
Data on D
Vitamin D refers to two biologically inactive precursors - D3, also known as cholecalciferol, and D2, also known as ergocalciferol. The former, produced in the skin on exposure to UVB radiation (290 to 320 nm), is said to be more bioactive.
Both D3 and D2 precursors are hydroxylated in the liver and kidneys to form 25- hydroxyvitamin D (25(OH)D), the non-active 'storage' form, and 1,25-dihydroxyvitamin D (1,25(OH)2D), the biologically active form that is tightly controlled by the body.
While our bodies do manufacture vitamin D on exposure to sunshine, the levels in some northern countries are so weak during the winter months that our body makes no vitamin D at all, meaning that dietary supplements and fortified foods are seen by many as the best way to boost intakes of vitamin D.
Source: British Journal of Cancer
Volume 101, Pages 916-923, doi:10.1038/sj.bjc.6605262
“Prospective study of predictors of vitamin D status and survival in patients with colorectal cancer”
Authors: K. Ng, BM Wolpin, JA Meyerhardt, K Wu, AT Chan, BW Hollis, EL Giovannucci, MJ Stampfer, WC Willett, CS Fuchs