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The Prediabetes Nutritionist

This Vitamin May Protect Women Against Early-Onset Colorectal Cancer

Eating vitamin D-rich foods may protect young women against early-onset colorectal cancer (CRC), a new observational study finds. 

Women under age 50 who consumed at least 11.25 mcg (450 IU) of vitamin D daily had a 49% lower risk of early-onset colorectal cancer than those consuming less than 7.5 mcg (300 IU). Moreover, food-derived vitamin D was more protective against colorectal cancer than supplements-derived vitamin D. 

The study, “Total Vitamin D Intake and Risks of Early-Onset Colorectal Cancer and Precursors,” was published in Gastroenterology.

Colorectal cancer is the second most common cancer among women worldwide, with 20% higher incidence rates and even higher mortality rates in African Americans than Caucasians. African Americans are more often diagnosed with colorectal cancer earlier, with more advanced disease than Caucasians. 

Until recently, colorectal cancer was more prevalent in people over age 50, but its rates in younger people –particularly those between 40 and 49 – have been steadily increasing. This worrisome trend has prompted guidelines to lower the age of colorectal cancer screening from 50 to age 45.

It is established that genetic, environmental, and lifestyle factors contribute to colorectal cancer risk. And while genetic factors are unmodifiable, lifestyle factors including overweight/obesity, poor diet, and physical inactivity are modifiable factors that may lower colorectal cancer risk if resolved. 

Diets rich in whole foods provide several antioxidants and micronutrients associated with lower colorectal cancer risk. Although past studies have linked vitamin D to lower colorectal cancer risk, it is still unclear if total vitamin D intake is associated with colorectal cancer risk, specifically in people under 50 years old.  

To learn more, a team of researchers investigated the association between total vitamin D intake and the risk of early-onset colorectal cancer and its precursors among women enrolled in the Nurses’ Health Study II – a prospective cohort study of nurses aged 25–42 years that began in 1989. 

The women complete questionnaires detailing demographics, diet, lifestyle factors, and other clinical and health-related information every two years. Based on the information provided, the researchers calculated the women’s total vitamin D intake from supplements and diet. They also determined colorectal cancer and precursor polyp rates among the women. 

A total of 94,205 women were enrolled in the study. 

Between 1991 and 2015, a total of 111 cases of colorectal cancer and 3,317 colorectal polyps were recorded. Analysis of the data showed that women under age 50 who consumed at least 11.25 mcg (450 IU) of vitamin D daily had a 49% lower risk of developing early-onset CRC than those consuming less than 7.5 mcg (300 IU). Younger women with higher vitamin D intakes also had a significantly lower risk of colorectal polyps. These associations were stronger in women who consumed vitamin D from dairy products than supplements. 

“We found that total vitamin D intake of 300 IU per day or more – roughly equivalent to three, eight-ounce glasses of milk – was associated with an approximately 50% lower risk of developing young-onset colorectal cancer,” Kimmie Ng, MD, MPH, of Dana-Farber Cancer Institute, said in a press release. 

Interestingly, there was no association between vitamin D intake and colorectal cancer or polyp risk in women over age 50. The authors could not explain this finding, noting that further research in larger samples was necessary to confirm if vitamin D’s protective effect against colorectal cancer was limited to younger adults. 

“Our results further support that vitamin D may be important in younger adults for health and possibly colorectal cancer prevention,” Ng said. “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,” she added. 

These findings may lead to recommendations for higher vitamin D intake in adults younger than 50 to complement current preventive screening tests. 

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