A new review of research indicates that maintaining adequate vitamin D levels may help lower the risk of developing colorectal cancer.
The analysis, which examined data from 50 studies involving more than 1.3 million participants, found a strong link between low vitamin D levels and a higher risk of colorectal cancer. A meta-analysis within the review showed people with higher blood levels of vitamin D had a 39% lower risk of colorectal cancer compared to those with lower levels.
When vitamin D levels were tracked over time, the risk reduction was 20%. Another landmark study from 1996 found women with the highest vitamin D intake were 58% less likely to develop colorectal cancer than those with the lowest intake.
Further research supports this connection. A Canadian study found vitamin D supplements reduced the risk of colon polyps by 33% and the risk of high-risk polyps by 43%. In the Iowa Women’s Health Study, women who took calcium and vitamin D supplements had a 15% lower risk of developing colorectal cancer.
Researchers suggest the active form of vitamin D in the body may protect against cancer by slowing cancer cell growth, triggering cell death, supporting a healthy gut microbiome, maintaining intestinal cell health, and reducing gut inflammation.
Despite the potential benefits, many people have low levels of the vitamin. A 2025 study of over 5,600 U.S. adults found that 42% were vitamin D deficient and 37.6% had insufficient levels. This means nearly 80% of adults studied had low vitamin D.
The researchers emphasize maintaining vitamin D blood levels between 30 and 40 ng/mL, noting many people would benefit from levels around 50 ng/mL. Vitamin D is found naturally in foods like cod liver oil, trout, and salmon, and in fortified foods like milk and eggs.
For individuals with low levels, a daily supplement containing 2,000 to 5,000 IU of vitamin D3 may be beneficial, with levels typically improving within a few months. Alongside maintaining vitamin D levels, regular health screenings starting at age 45 are recommended for early detection of colorectal cancer.
