Vitamin D may protect against young-onset colorectal cancer
Consuming higher amounts of Vitamin D — mainly from dietary sources — may help protect against developing young-onset colorectal cancer or precancerous colon polyps, according to researchers from the Dana-Farber Cancer Institute, the Harvard T.H. Chan School of Public Health and other US-based institutions.
Their study, published in the journal Gastroenterology, could potentially lead to recommendations for higher vitamin D intake as an inexpensive complement to screening tests as a colorectal cancer prevention strategy for adults under 50.
While the overall incidence of colorectal cancer has been declining, cases have been increasing in younger adults — a worrisome trend that has yet to be explained. The authors of the new study noted that vitamin D intake from food sources such as fish, mushrooms, eggs and milk has decreased in the past several decades. There is growing evidence of an association between vitamin D and risk of colorectal cancer mortality. However, prior to the current study, no research has examined whether total vitamin D intake is associated with the risk of young-onset colorectal cancer.
“Vitamin D has known activity against colorectal cancer in laboratory studies,” said Dr Kimmie Ng, Director of the Young-Onset Colorectal Cancer Center at Dana-Farber. “Because vitamin D deficiency has been steadily increasing over the past few years, we wondered whether this could be contributing to the rising rates of colorectal cancer in young individuals.”
The researchers calculated the total vitamin D intake — both from dietary sources and supplements — of 94,205 women participating in the Nurses’ Health Study II (NHS II), a prospective cohort study of nurses aged 25 to 42 years that began in 1989. During the period from 1991 to 2015 the researchers documented 111 cases of young-onset colorectal cancer (diagnosed before age 50) and 3317 colorectal polyps, which may be precursors to colorectal cancer.
Analysis showed that higher total vitamin D intake was associated with a significantly reduced risk of early-onset colorectal cancer. The same link was found between higher vitamin D intake and risk of colon polyps detected before age 50. The association was stronger for dietary vitamin D — principally from dairy products — than from vitamin D supplements, which the authors said could be due to chance or to unknown factors that are not yet understood.
“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 colorectal cancer,” Dr Ng said.
Interestingly, the researchers didn’t find a significant association between total vitamin D intake and risk of colorectal cancer diagnosed after age 50. They were not able to explain this inconsistency, and said further research in a larger sample is necessary to determine if the protective effect of vitamin D is actually stronger in young-onset colorectal cancer.
The investigators concluded that higher total vitamin D intake is associated with decreased risks of young-onset colorectal cancer and precursors (polyps). According to Dr Ng, “Our results further support that vitamin D may be important in younger adults for health and possibly colorectal cancer prevention.”
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