Nathan López Bezerra
By Molly Knudsen, M.S., RDN. April 19, 2026. Colon cancer rates are increasing at a high rate, especially among younger adults. While this cancer is still considered an age-related disease, environmental and lifestyle factors can spur or hasten its progression. Data indicate that around 50% of colon cancer cases can be prevented through lifestyle modifications.
One key area to focus on is vitamin D status. Decades of data indicate that vitamin D may be protective against colorectal cancers, whereas low levels of the vitamin are a risk factor.
To get a complete picture of this complex relationship, researchers recently reviewed data from 50 studies and over 1.3 million participants to reveal the role of vitamin D in colorectal cancer prevention.
Vitamin D Status and Intake Likely Reduce Colorectal Cancer Risk
The researchers found that low vitamin D levels are strongly linked to a higher risk of developing colorectal cancer. Among the 50 studies reviewed, the general findings from several major ones show a consistent pattern.
A meta-analysis showed that those with higher levels of vitamin D, measured via a blood test, had a 39% lower risk of colorectal cancer compared to those with lower levels. When vitamin D levels were tracked over time, people with higher levels had a 20% reduced risk of cancer.
A landmark study published in 1996 found that women with the highest vitamin D intake were 58% less likely to develop colorectal cancer than those with the lowest intake.
In the Danish “Diet, Cancer and Health” study, vitamin D seemed to have enhanced protective effects against colon cancer risk for those with a genetic risk.
In the Iowa Women’s Health Study, women who took calcium and vitamin D supplements had a 15% lower risk of developing colorectal cancer compared to those who did not take any supplements.
Another study found that increasing vitamin D intake reduced the risk of adenomas, which are polyps that may develop into cancer. A Canadian study showed vitamin D supplements reduced the risk of polyps by 33% and high-risk polyps by 43%.
How Does Vitamin D Protect Against Cancer?
While many studies in this review showed protective benefits of vitamin D, most were not able to pinpoint the exact mechanisms through which these benefits occurred. However, laboratory, animal, and other human studies indicate that the active form of vitamin D in the body, calcitriol, may target colon cancer progression in several ways.
These include slowing down the growth of cancer cells, triggering cell death, supporting a balanced gut microbiome, keeping intestinal cells healthy, and reducing gut inflammation.
Most People Have Low Vitamin D Levels
Vitamin D can be protective against colorectal cancer in addition to aiding other bodily functions from immunity to mood. But most people have very low levels of the vitamin.
A 2025 study that looked at the impact of vitamin D levels and muscle mass of over 5,600 U.S. adults found that 42% were vitamin D deficient, with blood levels less than 20 ng/mL. Another 37.6% had vitamin D insufficiency, with blood levels between 20 and 30 ng/mL. Only about 20% had sufficient vitamin D status, with blood levels of 30 ng/mL or higher. This means nearly 80% of people had low vitamin D levels.
Researchers of this review emphasized the importance of having vitamin D levels in the 30 to 40 ng/mL range, noting many people would benefit from a status of 50 ng/mL.
Increasing Your Vitamin D Levels
Vitamin D is naturally found in some foods, such as cod liver oil, trout, and salmon, or in fortified foods like milk and eggs. However, many people, especially those with low vitamin D levels, would benefit from a high-quality vitamin D supplement.
A common guideline is to look for supplements that provide 2,000 to 5,000 IU of vitamin D3, not D2, and to take it daily. Vitamin D levels should start to improve within a few months.
The Takeaway
Vitamin D status is one lifestyle factor connected to colorectal cancer risk, and one that can be improved with supplementation. Regular screenings, starting at age 45, are important for early detection and treatment of any concerning findings.
Research into nutritional prevention of chronic diseases is ongoing. The relationship between diet and cancer risk continues to be a major focus for public health officials. Many health agencies recommend discussing individual risk factors and nutritional needs with a doctor or registered dietitian.
