By Molly Knudsen, M.S., RDN on April 19, 2026
A new study indicates that vitamin D may lower the risk of colon cancer by up to 58 percent. Colon cancer rates are rising, particularly among younger adults.
Data show that about half of colon cancer cases can be prevented through lifestyle changes. Vitamin D status is a key area, with decades of data suggesting it may protect against colorectal cancers, while low levels are a risk factor.
Study Findings
Researchers recently reviewed data from 50 studies and over 1.3 million participants to understand vitamin D’s role in colorectal cancer prevention. They found that low vitamin D levels are strongly linked to a higher risk of developing this cancer.
One meta-analysis showed that people with higher vitamin D levels had a 39 percent lower risk of colorectal cancer compared to those with lower levels. When tracked over time, higher levels were associated with 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.
In the Danish “Diet, Cancer and Health” study, vitamin D seemed to offer enhanced protection against colon cancer risk for those with a genetic predisposition.
The Iowa Women’s Health Study reported that women taking calcium and vitamin D supplements had a 15 percent lower risk of colorectal cancer compared to non-users.
Other research indicated that increasing vitamin D intake reduced the risk of adenomas, which are polyps that may become cancerous. A Canadian study found vitamin D supplements lowered polyp risk by 33 percent and high-risk polyp risk by 43 percent.
How Vitamin D Protects Against Cancer
While many studies show protective benefits, most do not pinpoint exact mechanisms. However, lab, animal, and human studies suggest the active form of vitamin D, calcitriol, may slow cancer cell growth, trigger cell death, support a balanced gut microbiome, maintain intestinal cell health, and reduce gut inflammation.
Low Vitamin D Levels in the Population
Most people have low vitamin D levels. A 2025 study of over 5,600 U.S. adults found that 42 percent were vitamin D deficient, 37.6 percent had insufficiency, and only about 20 percent had sufficient levels. This means nearly 80 percent of adults have low vitamin D.
Researchers stress the importance of maintaining vitamin D levels between 30 and 40 nanograms per milliliter, with some benefiting from levels up to 50 ng/mL.
Increasing Vitamin D Levels
Vitamin D is naturally found in foods like cod liver oil, trout, and salmon, or in fortified items such as milk and eggs. For many, especially those with low levels, a high-quality vitamin D supplement may be helpful.
A common suggestion is to take supplements providing 2,000 to 5,000 international units of vitamin D3 daily, which can improve levels within a few months.
Takeaway
Vitamin D status is one lifestyle factor linked to colorectal cancer risk that can be improved with supplementation. Regular screenings starting at age 45 are also emphasized for early detection and treatment.
Colon cancer remains a significant health concern, and understanding modifiable risk factors like vitamin D is part of broader prevention efforts. Public health guidelines often recommend a combination of diet, supplements, and medical check-ups to address such risks, aligning with the study’s focus on actionable lifestyle changes.
