Higher vitamin D intake may decrease risk for CRC
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Higher intake of vitamin D correlated with a decreased risk for early-onset colorectal cancer and CRC precursors among a cohort of young women, according to research published in Gastroenterology.
“Despite a decline in the overall incidence of CRC in many countries, including the U.S., the incidence of CRC in younger adults has been rising. ... Because a substantial proportion of early-onset CRC patients do not have a family history of CRC or known hereditary syndrome, recent changes in lifestyle factors and dietary patterns are hypothesized to contribute to the increasing incidence of early-onset CRC,” Hanseul Kim, PhD, Harvard T.H. Chan School of Public Health, and colleagues wrote. “Vitamin D intake represents a possible factor that may contribute to the recent increase in early-onset CRC incidence.”
Researchers prospectively analyzed 94,205 women aged 25 years to 42 years enrolled in the Nurses’ Health Study II from 1991 to 2015 to investigate the association between total vitamin D intake and CRC. During 1,250,560 person-years of follow-up, there were 111 incident cases of early-onset CRC.
Compared with women who consumed less than 300 IU per day of total vitamin D, women who consumed 300 IU per day to less than 450 IU per day (HR = 0.51; 95% CI, 0.3-0.86) and those who consumed more than 450 IU per day of total vitamin D had a reduced risk for early-onset CRC (HR = 0.49; 95% CI, 0.26-0.93). Further, dietary sources of vitamin D had a stronger inverse association compared with supplemental vitamin D (per 400 IU/day increase: HR = 0.34; 95% CI, 0.15-0.79 vs. HR = 0.77; 95% CI, 0.37-1.62). Researchers noted higher total vitamin D intake also correlated with a lower risk for conventional adenomas (OR = 0.76; 95% CI, 0.65-0.88) and serrated polyps (OR = 0.85; 95% CI, 0.75-0.97).
“We found that total vitamin D intake of 300 IU per day or more – roughly equivalent to three 8 oz glasses of milk – was associated with an approximately 50% lower risk of developing young-onset CRC,” Kimmie Ng, MD, MPH, Dana-Farber Cancer Institute, said in a press release. “Our results further support that vitamin D may be important in younger adults for health and possibly CRC prevention. It is critical to understand the risk factors that are associated with young-onset CRC so that we can make informed recommendations about diet and lifestyle as well as identify high risk individuals to target for earlier screening.”
Perspective
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Mohamad Mouchli, MD
The growing evidence linking vitamin D deficiency with risk for colorectal cancer is receiving considerable attention. This fine study was conducted to assess the association between vitamin D deficiency and early-onset CRC in women aged 25 to 42 years. About nine of 100,000 women developed early-onset CRC. Supplemental vitamin D consumption associated with a reduced risk for early-onset CRC, conventional adenomas and serrated lesions. Interestingly, dietary vitamin D had the strongest inverse association with early-onset CRC.
The rising incidence of early-onset CRC is a difficult challenge. Studying dietary diseases, lifestyle habits and factors affecting the human microbiome could help solve the mystery. The high prevalence of vitamin D deficiency among patients with several cancers, including CRC, suggest that vitamin D deficiency may account for morbidity and mortality from cancer. Vitamin D may help enhance the innate immune system through different mechanisms. It was estimated that 40% of the U.S. population and 1 billion of people worldwide have vitamin D deficiency. Residents of the northern tier of the U.S. are at an increased risk since they receive less solar ultraviolet B and should be considered for screening for vitamin D deficiency. The deficiency is more prevalent in fall and winter. Vitamin D replacement may help reduce early-onset CRC incidence at low cost (ie, the cost of a daily dose of 1,000 IU of vitamin D3), with no to very low adverse effects. Another potential solution is to look for dietary resources with extra calcium for extra prevention. Patients can be encouraged to ask about their vitamin D levels when they visit their primary care physician. The target range for serum vitamin D based on gender and racial differences is still to be determined.
“You are what you eat,” is what I tell my young and healthy patients when they ask me what to do to protect themselves from getting early-onset CRC. “Prevention is better than cure,” are my words for those who are skeptical about the role of dietary and lifestyle modifications. These remain acceptable answers until we get further prospective studies to determine all dietary factors associated with early-onset CRC and determine if there is a causation, not only an association, between these factors and early-onset CRC.
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