A study from the Slone Epidemiology Center and the Boston University School of Medicine suggests that Black women with a low vitamin D status have an increased risk of developing colorectal cancer (CRC), in line with the findings of previous epidemiologic studies conducted in White populations. These findings, ‘Predicted Vitamin D Status and Colorectal Cancer Incidence in the Black Women's Health Study, appear in the journal Cancer Epidemiology, Biomarkers & Prevention.
"Our findings, taken together with established evidence that vitamin D levels are generally lower in the Black population than other groups, suggest that low vitamin D may contribute to disproportionately high colorectal cancer incidence among Blacks," said corresponding author, Dr Julie Palmer, director of BU's Slone Epidemiology Center and the Karin Grunebaum Professor in Cancer Research at Boston University School of Medicine.
Vitamin D plays a role in many cellular processes in the human body and has been shown to have anti-cancer properties. It is possible that having sufficient levels of vitamin D circulating through the body may reduce the risk of developing colorectal cancer, which is a disease that affects over 150,000 individuals each year. The Black population tends to have lower levels of vitamin D because the major source of vitamin D, aside from taking vitamin D supplements, is from sunlight. They also are disproportionately burdened by colorectal cancer, with the highest rates of both incidence and mortality.
To determine vitamin D levels prior to the cancer diagnosis, the researchers developed a set of the best predictors for correctly classifying a study participant as to her rank on a scale of possible vitamin D levels from very low to very high. The prediction model derived by this process weighted variables by how strongly they were associated with actual blood levels. The researchers then applied that model to all participants in the Black Women's Health Study (49,534 participants) to get a predicted vitamin D score that would likely correspond well to their relative level.
Over follow-up, 488 incident colorectal cancers occurred - compared with women in the highest quartile of predicted vitamin D score, those in the lowest had an estimated 41% (HR = 1.41; 95% CI, 1.05–1.90) higher colorectal cancer risk. Comparable HRs were 1.44 (95% CI, 1.02–2.01) for colon and 1.34 (95% CI, 0.70–2.56) for rectal cancer.
The researchers believe it is important to determine if there is a relationship between vitamin D status and CRC risk in a Black population, so that individuals who are at an increased risk of CRC can implement strategies to increase the levels of vitamin D in their bodies.