Vitamin D May Lower Your Colon Cancer Risk

Colorectal cancer (CRC) is one of the leading cancers worldwide, especially in countries that follow a Western lifestyle and diet. Worldwide, 1.2 million new CRC cases are diagnosed each year, making it the second most common cancer in men and the third most common in women. 

In the U.S., colorectal cancer is the third most common cancer diagnosed in American men and women, excluding skin cancers. The lifetime risk for developing CRC is about one in 24 for men and one in 26 for women, depending on risk factors.

Scientists are always looking for ways to reduce the risk of diseases like CRC, which includes cancers of the colon and rectum. In a review of previously published studies, researchers focused on the relationship between vitamin D and CRC. They published the review in April 2025 in Nutrients. Let’s break down their findings.

How Was This Study Conducted?

This study was a review, meaning that the researchers assessed a variety of previous studies to look for overarching connections the results shared.

Researchers searched scientific databases for studies on CRC and vitamin D. While they initially found over 10,000 studies, they ended up with 50 after sifting through them and removing duplicates and those that didn’t meet their criteria. 

Specifically, the researchers only wanted to include studies in adult human participants who either had CRC (or precursors for CRC) or had a documented vitamin D deficiency. They also sought out cases where participants were given a vitamin D supplement as part of the study.

What Did It Show?

According to these researchers, vitamin D has been shown to have many benefits in our bodies, including supporting communication between nerve cells, regulating blood pressure and preventing respiratory infections. It plays roles in maintaining gut health, thyroid hormone levels, blood sugar levels and even mitigating the harmful effects of aging. Vitamin D also acts as an antioxidant, reducing inflammation, suppressing autoimmune responses and supporting the function of immune cells.

The researchers also cite a previous study that suggests that vitamin D inhibits uncontrolled cell growth and the formation of new blood vessels that “feed” cancer cells (called angiogenesis) and promotes apoptosis (killing abnormal cells).

So what did these researchers find regarding vitamin D and CRC? While there was some conflicting evidence, they state that vitamin D deficiency is strongly linked to an increased risk of CRC, partly because that deficiency exacerbates intestinal inflammation, which promotes CRC progression.

Specifically, one meta-analysis of 31 original studies reported that compared to the lowest dietary intake of vitamin D (10 ng/mL), the highest amount (80 ng/mL) showed a 25% reduction in CRC risk. 

The Nurses’ Health Study, a common long-term U.S. study used to find connections between lifestyle factors and disease risk, showed that women with the highest vitamin D intake had a 58% reduced risk of CRC compared to those with the lowest intake. 

The Iowa Women’s Health Study found that those in the highest calcium and vitamin D intake reduced their risk of CRC by about half. The Spanish PREDIMED study had similar results, as did studies that used vitamin D supplementation (as opposed to getting it through food). 

Polyps and adenomas are precursors to CRC and are commonly found and removed during colonoscopies. Researchers found evidence that vitamin D can also help prevent polyps. For example, a Canadian study with 1,409 participants found that vitamin D supplementation reduced the probability of polyp development by 33% and the risk of high-risk adenomatous polyps by 43%. 

Overall, researchers found that vitamin D, both dietary and supplemented, plays a crucial role in preventing and treating colorectal cancer by reducing inflammation, regulating immune responses, promoting cancer cell death and inhibiting tumor growth. For those who have CRC, vitamin D may help promote better survival rates and reduce death rates from CRC. 

There were a few limitations to this review. First, though many studies showed protective benefits of vitamin D on CRC, most could not define the mechanisms through which these benefits occurred. Study authors also state that more large-scale, randomized clinical trials need to be done, which will provide more answers, including optimal dosage and formulations of vitamin D supplements. 

How Does This Apply to Real Life?

Based on the evidence in this review, vitamin D appears to help prevent CRC and may help people with CRC survive it. Unfortunately, vitamin D is a commonly deficient vitamin. Worldwide, vitamin D deficiency is estimated to range from 30% to 50%, with even higher rates seen in specific populations.

Risk factors for vitamin D deficiency include being a woman, living in regions that experience colder winter climates, having darker skin and living in a low- and middle-income country where proper nutrition and supplements may be more limited. 

Besides having a genetic predisposition for CRC, other risk factors include older age, sedentary lifestyle and a diet high in unhealthy fats and red meat and low in fiber. An imbalanced gut microbiome also plays a role, as do having inflammatory bowel disease, obesity, frailty and diabetes. 

Vitamin D is called the sunshine vitamin because your body manufactures it with UVB rays exposure—aka sunshine. But if you live in regions that experience cold winters, it can be difficult or impossible to get enough sun exposure during those months. In the warmer months, you should consider your skin cancer risk and balance it with sun exposure. You also need to have enough skin exposure to make vitamin D—face, arms and legs. Plus, pollution, darker skin and possibly sunscreen reduce sunlight absorption, reducing vitamin D production. For these reasons, diet and supplementation may be more reliable avenues for getting enough vitamin D. 

Because it is possible to overdo it and end up with vitamin D toxicity, before you start putting the vitamin D supplements to use, it helps to know your blood levels. This can be done by requesting a blood test from your primary care practitioner. If you end up being deficient, meeting with a registered dietitian can help you figure out what foods and how much of each you need to eat each day to get your levels up. An RD can also help you supplement, if that is your desire or if it’s recommended. 

Another finding from this review was that healthy eating patterns, like the Mediterranean diet, tend to be plentiful in vitamin D and other anti-inflammatory nutrients. The Mediterranean diet is rich in fruits, vegetables, nuts, seeds, whole grains, fish, dairy and healthy fats. While there aren’t a lot of food sources of vitamin D, ones that contain it include egg yolks, fatty fish (like salmon, tuna, mackerel and sardines) and mushrooms. Fortified dairy and orange juice also contain vitamin D. Researchers note that a holistic dietary approach may be a better strategy than focusing on one isolated nutrient. 

The Bottom Line

This review of 50 studies found a strong connection between adequate vitamin D levels and a reduced risk of colorectal cancer. Because vitamin D deficiency is so common, it can be helpful to have bloodwork to test your levels. Based on the results, if you need to increase your levels, try adding foods rich in vitamin D, including whole eggs, salmon, mushrooms and fortified dairy products, like milk and yogurt, to your diet. Following a healthy eating pattern, like the Mediterranean diet, can also be beneficial.

If you choose to supplement, work with a registered dietitian or your primary care practitioner to determine the best dose for you. When possible, spend time outside to catch some rays. Being outdoors also has mental health and mood benefits—all the better if your physical activity is performed outside.