Vitamin D plays an important role in maintaining bone health, it was hypothesized colorectal cancer risks could be lowered via several pathways related to cell growth and regulation. Several studies have previously yielded inconsistent results whether higher concentrations of circulating 25-hydroxyvitamin D are linked to lower risk of colorectal cancer.
Participant level data collected before cancer diagnosis was analyzed from 17 prospective cohorts using standardized criteria across the studies, which included over 5,700 colorectal cancer cases and 7,100 controls from Asia, USA, and Europe. A single accepted assay and laboratory was used for vitamin D measurements and calibration of existing measurements, calibrated approach enabled systematic exploration risk over broad range of vitamin D levels observed internationally.
Subjects with deficient concentrations of vitamin D were found to be at 31% higher risk of colorectal cancer during 5.5 year follow up. Subjects with concentrations above bone health sufficiency were at 22% lower risk for colorectal cancer at follow up; risk did not continue to decline at higher concentrations. Associations persisted after adjusting for known risk factors, protective association was seen in all subgroups, with the association being noticeably stronger in women at concentrations above bone health sufficiency.
Lifetime colorectal risk for cancer is 4.5% for men and 4.2% for women. Colorectal cancer is the third leading cause of cancer death, and the third most common cancer within the USA, with 140,250 new cases and 50,630 deaths being predicted for 2018.
Vitamin D can be obtained from sun exposure, in diet, and supplements. Experts recommend that vitamin D be obtained through diet as much as possible due to excessive exposure to the sun’s ultraviolet radiation being considered to be a serious risk factor for skin cancer.
Collaborative medical centers and organizations included: The American Cancer Society, the U.S National Cancer Institute, and the Harvard T.H. Chan School of Public Health, among 20 others.
