Vitamin D & Cancer Risk
Several studies have shown that Vitamin D correlates with cancer risk. However, the benefits of vitamin D might not be obtained by taking supplements. Rather, vitamin D levels may be an indicator of a healthy lifestyle.
Professionally Reviewed by Charles Li, MD


Vitamin D

Why Vitamin D Matters

Vitamin D is one of the most important vitamins. It plays an important role across systems throughout your body, not just your bones. Recently, studies have linked Vitamin D levels to cancer risk.

what is it?
where to get it
Vitamin D
what is it?
Key Facts
  • type
    fat soluble
  • source
    diet, skin
  • other names
    calciferol, cholecalciferol
Use List

bone growth



Vitamin D
where to get it
the sun

your body can create vitamin D with assistance from the sun


some foods such as milk and fish contain vitamin D


Vitamin D can also be obtained from dietary supplements

Key facts: Vitamin D plays a key role in bone growth, calcium absorption, and your immune system. Unlike some vitamins, your body can produce it with the help of the sun. Sunlight helps catalyze a key reaction in the production of Vitamin D.


Vitamin D and Colon Cancer

A Case-Control study of 179 colorectal cancer patients and 356 matched controls found that high Vitamin D levels in the blood was associated with a significantly lower risk of developing Colon Cancer and Colorectal Cancer compared to having low levels of Vitamin D in the blood.

What this means

This study showed that vitamin D levels in the blood correlated with a lower risk of developing Colon Cancer and Colorectal cancer. While it doesn’t say whether vitamin D is causing a benefit, it does show that those who have lots of vitamin D tend to have a lower risk.

Author Quote

"We investigated this relationship in a nested case-control study within the Health Professionals Follow-up Study (HPFS), a large ongoing study of male health professionals living in the United States.......Our data provide additional support for the inverse association between vitamin D and colorectal and, in particular, colon cancer risk."

Source: A nested case control study of plasma 25-hydroxyvitamin D concentrations and risk of colorectal cancer


Vitamin D & Breast Cancer Risk
Vitamin D & Breast Cancer Risk

This study found that individuals with high vitamin D levels had a significantly lower risk of breast cancer compared to those with low Vitamin D. This was calculated by combining data from 11 studies, a meta-analysis, and was found to be statistically significant.

From the study

"This study supports the hypothesis that higher serum 25(OH)D levels reduce the risk of breast cancer. According to the review of observational studies, a serum 25(OH)D level of 47 ng/ml was associated with a 50% lower risk of breast cancer."

Source: Serum 25-hydroxyvitamin D and prevention of breast cancer: pooled analysis

Why This Matters

Similar to the Colon Cancer data, this research further demonstrates that those who have high vitamin D levels in their blood have a significantly lower risk of developing cancer.

Negative Clinical Trial Results

Clinical trials have not shown benefits to vitamin D supplements.

Supplements may not work

While having high blood levels of Vitamin D shows clear benefits, taking vitamin D supplements may not show benefits for cancer risk as shown by the study below.

Vitamin D & Invasive Cancer Risk: Clinical trial results chart

A clinical trial showed that vitamin D supplements did not reduce cancer risk. Researchers studied 25,871 participants over 5.3 years. Participants were randomized to receive either a placebo or a daily vitamin D supplement.

From the study:

"In this large primary-prevention trial, supplementation with vitamin D3 (at a dose of 2000 IU per day) did not lead to a significantly lower incidence of invasive cancer of any type or a composite of major cardiovascular events (myocardial infarction, stroke, and death from cardiovascular causes) than placebo. The intervention also did not lead to a lower incidence of total deaths from cancer or a lower incidence of breast, prostate, or colorectal cancer than placebo."

Source: Vitamin D Supplements and Prevention of Cancer and Cardiovascular Disease

Our Take

Vitamin D & Cancer Risk

Key Takeaways

Blood levels of Vitamin D have consistently shown a correlation with a lower risk of developing cancer. However, clinical trials show that taking supplements may not reduce your risk of developing cancer. This suggests that the benefits of vitamin D cannot be obtained by taking supplements. Rather, vitamin D levels may be an indicator of a healthy lifestyle. As always, diet and exercise are a safe bet.


How Vitamin D is Made
Chart of how vitamin D is made

How Vitamin D is Made: Skin cells are believed to create 7-Dehydrocholesterol. UVB Rays from the sun convert this to Vitamin D3. Your liver and kidneys convert this to active Vitamin D. Vitamin D is then distributed throughout the body.

More Information

Vitamin D & Cancer

"Intake of vitamin D through diet may protect against breast or colorectal cancers or affect markers for prostate cancer. However, vitamin D by itself does not prevent or treat cancer. Other large studies show that high vitamin D levels do not reduce the risk of many other cancers, and may increase risk for pancreatic or aggressive prostate cancer. More studies are needed to evaluate vitamin D in different populations."

Getting Vitamin D

"During the fall and winter months, the sun’s rays are weaker and many Canadians spend more time indoors, away from direct sunlight. Canadians may need to take a vitamin D supplement during these months. Talk to your doctor about whether taking 1000 international units (IU) a day in the fall and winter is right for you. Babies who are exclusively breast-fed may be at risk of vitamin D deficiency, which is why experts recommend giving them a vitamin D supplement of 400 IU a day."

Genetics & Vitamin D

"Assessments of whether or not vitamin D can reduce cancer risk also need to consider genotypes of vitamin D-associated genes. This was discussed at length above, but further supported by results of a randomized placebo-controlled study that showed vitamin D supplementation (1,000 IU/day) significantly reduced development of advanced colorectal adenomas in subjects with the VDR rs7968585 AA genotype, but increased the risk in those with AG or GG genotyp"