Findings from a study in the journal Gastroenterology that was conducted by researchers from Dana-Farber Cancer Institute, the Harvard T.H. Chan School of Public Health, and other institutions could potentially lead to recommendations for higher vitamin D intake as an inexpensive complement to screening tests as a colorectal cancer (CRC) prevention strategy for adults younger than age 50 years.
The study authors noted that there is expanding evidence of a correlation between vitamin D and increased risk of CRC mortality. However, prior to the current study, no research had investigated whether total vitamin D intake is linked to the risk of young-onset CRC. The researchers examined the association between total vitamin D intake and risks of early-onset CRC and precursors among women enrolled in the Nurses' Health Study II (NHS II). Multivariable-adjusted hazard ratios (HRs) and 95%CIs for early-onset CRC were estimated with the Cox proportional-hazards model. Multivariable-adjusted odds ratios (ORs) and 95% CIs for early-onset conventional adenoma and serrated polyp were evaluated with the use of the logistic-regression model.
The results were obtained by calculating the total vitamin D intake—from both dietary sources and supplements—of 94,205 women in NHS II, which was a prospective cohort study of nurses aged 25 to 42 years that began in 1989. The women were followed every 2 years via questionnaires on demographics, diet, lifestyle, medical issues, and other health-related information. The researchers concentrated on a primary endpoint: young-onset CRC diagnosed before age 50 years. The researchers also queried subjects via follow-up questionnaire on whether they had had a colonoscopy or sigmoidoscopy to detect colorectal polyps (which may be precursors to CRC).
The researchers documented 111 incident cases of early-onset CRC during 1,250,560 person-years of follow-up (1991-2015). Higher total vitamin D intake was substantially linked to a reduced risk of early-onset CRC (HR for >450 IU/day vs. <300 IU/day, 0.49; 95% CI, 0.26-0.93; P for trend = .01). The HR per 400 IU/day increase was 0.46 (95% CI, 0.26-0.83).
The inverse correlation was considerable and appeared more evident for dietary sources of vitamin D (HR per 400 IU/day increase, 0.34; 95% CI, 0.15-0.79) than supplemental vitamin D (HR per 400 IU/day increase, 0.77; 95% CI, 0.37-1.62). For CRC precursors, the ORs per 400 IU/day increase were 0.76 (95% CI, 0.65-0.88) for conventional adenoma (n = 1,439) and 0.85 (95% CI, 0.75-0.97) for serrated polyp (n = 1,878).
The researchers concluded that in a cohort of younger women, a higher trial intake of vitamin D was linked to diminished risks of early onset CDC and precursors.
In an interview, Kimmie Ng, MD, MPH, director of the Young-Onset Colorectal Cancer Center at Dana-Farber, stated, "Our results further support that vitamin D may be important in younger adults for health and possibly colorectal cancer prevention. It is critical to understand the risk factors that are associated with young-onset colorectal cancer so that we can make informed recommendations about diet and lifestyle, as well as identify high risk individuals to target for earlier screening."
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