A new review of research indicates that maintaining adequate vitamin D levels may help lower the risk of developing colorectal cancer, with some studies showing risk reduction as high as 58 percent. The findings come as colon cancer rates are rising, particularly among younger adults.
Researchers analyzed data from 50 studies involving more than 1.3 million participants to understand the link between vitamin D and colorectal cancer prevention. The analysis showed that low vitamin D levels are strongly associated with a higher risk of this type of cancer.
A key meta-analysis found that individuals with higher blood levels of vitamin D had a 39 percent lower risk of colorectal cancer compared to those with lower levels. When levels were tracked over time, those with higher levels saw a 20 percent reduced risk.
A landmark study from 1996 found that women with the highest vitamin D intake were 58 percent less likely to develop colorectal cancer than those with the lowest intake. Other studies, including the Iowa Women’s Health Study, showed that women taking calcium and vitamin D supplements had a 15 percent lower risk.
Further research points to specific protective effects. A Canadian study found vitamin D supplements reduced the risk of polyps by 33 percent and high-risk polyps by 43 percent. Another study noted that increasing vitamin D intake reduced the risk of adenomas, which are polyps that can develop into cancer.
How Vitamin D Protects Against Cancer
While the exact mechanisms are still being studied, laboratory, animal, and some human research suggests the active form of vitamin D in the body, calcitriol, may combat colon cancer progression in several ways. These include slowing cancer cell growth, triggering cell death, supporting a balanced gut microbiome, maintaining healthy intestinal cells, and reducing gut inflammation.
Despite these potential benefits, a significant portion of the population has low vitamin D levels. A 2025 study of over 5,600 U.S. adults found that 42 percent were deficient, 37.6 percent had insufficiency, and only about 20 percent had sufficient levels. This means nearly 80 percent of adults had low vitamin D.
The researchers emphasize the importance of maintaining blood levels between 30 and 40 nanograms per milliliter, noting many could benefit from levels around 50 ng/mL.
Increasing Your Vitamin D Levels
Vitamin D is found naturally in some foods like cod liver oil, trout, and salmon, and is added to fortified foods like milk and eggs. However, many people, especially those with low levels, may benefit from a supplement.
A common recommendation is to look for supplements providing 2,000 to 5,000 International Units of vitamin D3, taken daily. Levels typically begin to improve within a few months of consistent supplementation.
Vitamin D status is one modifiable lifestyle factor linked to colorectal cancer risk. Experts also stress the importance of regular screening for early detection, which is recommended to begin at age 45 for most adults.
