Published on March 24, 2021

What is Vitamin D Good For? (Part 7: Cancer Prevention) – Vitamin D is needed by virtually every cell in the body, and is essential for hundreds of processes each and every day

Cancer Prevention Awareness Week (March 20-26, 2021) has been launched to help people better understand the links between cancer and diet, lifestyle, weight, and other factors, as well as the steps they can take on a daily basis to help reduce cancer risk.

Vitamin D has known anticancer effects, and much research has been published over the last several decades showing a link between vitamin D levels and cancer risk. Depending on the type of cancer, vitamin D alone can potentially reduce the risk of cancer by about 25% to 80%! Today, as part of our What is Vitamin D Good For? series, we will focus on how vitamin D can help reduce cancer.

Since vitamin D acts as a protector and regulator, it is able to enhance the functioning of all types of cells, tissues and organs to keep us healthy. So far in this series, we have covered how vitamin D contributes to the health of the musculoskeletal system, dermatological system, reproductive system, respiratory system, cardiovascular system, and to cognitive and mental-emotional wellness. A deficit in vitamin D can lead to impairment or disease in each of these systems – from brittle bones to heart disease, cancer and dementia. With this in mind, why take a chance at being deficient in vitamin D?

Summary of Overall Benefits of Vitamin D to Help Fight & Prevent Cancer

Anti-cancer functions of vitamin D include:

  • Inhibits cancer cell growth and proliferation
  • Reduces cancer metastasis
  • Stimulates maturation of healthy cells (differentiation)
  • Induces death of cancer cells (apoptosis or programmed cell death)
  • Prevents blood vessel growth in tumors (angiogenesis)
  • Prevents inflammation associated with cancer
  • Reduces the risk of incidence and/or death due to cancer

Cancers associated with low vitamin D include:

Vitamin D is a Likely Causal Factor for Cancer Risk Reduction

The evidence associating vitamin D and cancer is so strong that vitamin D is now thought to be a causal factor in the risk-reduction of most types of cancer. Causation can be determined using Hill’s criteria for causality, a scientific set of guidelines for looking at data based on the strength of association, consistency between studies, temporality, biological gradient, plausibility, coherence with known scientific facts, experiment, and analogy. Two separate publications (WB Grant and Mohr et al.) have confirmed vitamin D as a causal risk-modifying factor for most cancers using Hill’s criteria.

How Vitamin D Fights Cancer

The active form of vitamin D, calcitriol, controls multiple pathways associated with the life cycle of the cell including those involved with reproduction, maturation and programmed death. Calcitriol regulates the production of a number of signals and growth factors at the genetic level. As detailed in the table below, some of the signals turned on by vitamin D stimulate growth, development, maturation and programmed cell death while other signals inhibit inflammation, prevent blood vessels from being made that can feed cancer cells, and stop the spread of the cancer to other parts of the body.

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Specifically, calcitriol stops the uncontrolled reproduction of cancer cells by decreasing production of growth factors and increasing “stop” signals. In addition, calcitriol pushes the cell towards maturation and away from reproduction, and can also activate an internal process that starts programmed cell death in the cancerous cell. Part of the process for cancer growth and metastasis involves creating an inflammation response, building new blood vessels within the tumor, and breaking up surrounding tissue to allow the cancer to spread to other parts of the body. Calcitriol prevents inflammation, new blood vessel growth (called angiogenesis) and spread through inhibiting the signals needed.

Interestingly, some cancer cells find ways to stop vitamin D metabolism by the cell (by preventing the vitamin D receptor from being expressed, increasing the breakdown of calcitriol, or decreasing the production of calcitriol), which may help the cancer evade detection and continue to grow.

GrassrootsHealth Analysis Shows 71% Lower Cancer Risk

In April 2016, GrassrootsHealth partnered with leading vitamin D and cancer researchers Drs. Garland, Gorham, Heaney, and Lappe to publish Serum 25-Hydroxyvitamin D Concentrations ≥40 ng/ml Are Associated with >65% Lower Cancer Risk: Pooled Analysis of Randomized Trial and Prospective Cohort Study, a paper focused on achieved vitamin D serum levels and cancer incidence. Data was combined for women 55 and older from our GrassrootsHealth cohort (N = 1,135, median serum level = 48 ng/ml or 120 nmol/L) and the cohort of a previously published randomized controlled trial (RCT) of vitamin D and calcium supplementation with respect to cancer (Lappe RCT paper; N= 1,169, median serum level = 30 ng/ml or 75 nmol/L). The pooled cohort was analyzed to investigate cancer incidence over time (median = 3.9 years) for all invasive cancers combined, excluding skin cancer. Pooling the data allowed for a broader range of serum levels, more data, and thus improved statistical power.

In the analysis, without adjusting for other risk factors, we found that women with a mean vitamin D serum level greater than or equal to 40 ng/ml (100 nmol/L) had a 71% lower risk of cancer than women with serum levels <20 ng/ml (<50 nmol/L; P-value = .02). The greatest decrease in risk occurred between about 10 – 40 ng/ml (25 – 100 nmol/L).

The graph below shows the plot of cancer incidence versus vitamin D level. The blue dotted lines are called the ‘confidence interval’, the closer they are to the actual plotted line (green line) the surer we are of the data, meaning the more data points we had in this region to ensure accuracy. Because we used D*action data with the Lappe data, we had a lot of people in the 40-60 ng/ml range (our recommended range) and can say clearly that cancer incidence is much lower when vitamin D levels are within this range.

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This second look at the combined data uses a Kaplan Meier curve to clearly illustrate the difference between the proportions of cancer-free participants at the end of the 4 year observation period.

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The lines in the chart above represent the percent of participants without cancer for each vitamin D level group. Lines that are closer to the bottom of the chart represent higher cancer incidence and lines that are closer to the top of the chart represent lower cancer incidence.

VITAL Trial Shows Cancer Risk Reduction with Vitamin D Stronger when BMI Considered

The VITAL trial was a recent, randomized, double blind, placebo-controlled clinical trial conducted in multiple centers around the United States. It included 25,871 participants who were free of cancer and cardiovascular disease diagnoses at baseline. Participants were given 2000 IU vitamin D per day and 1 gram of marine omega-3 fatty acids per day, or placebo. The average vitamin D level at baseline among all participants was about 30 ng/ml (75 nmol/L).

Initial findings from the VITAL trial were published in November of 2018; one paper compared cancer outcomes between those assigned to vitamin D (2000 IU/day) vs. placebo. When cancer outcome results were analyzed excluding the first two years after study initiation (allowing time for vitamin D to have an effect), there was a 25% reduced risk of cancer mortality among those taking vitamin D (p=0.02).

In the VITAL trial, vitamin D levels varied significantly by BMI at baseline and after one year of supplementation. In participants with a normal BMI (25 to 30) average vitamin D levels increased from 29.5 ng/ml at baseline to 41.4 ng/ml at follow-up – meaning that only half of the participants achieved levels above 40 ng/ml (100 nmol/L) with 2,000 IU of vitamin D supplementation. In comparison, in those who were overweight (BMI above 30), average vitamin D levels did not reach 40 ng/ml, only increasing from 26.7 ng/ml at baseline to 38.6 ng/ml at one year.

When taking BMI into consideration for the analysis, the reduction in cancer was more pronounced. A significant reduction of metastatic or fatal cancer was seen among those with a normal BMI, with a decreased risk of 38% among those taking vitamin D compared to placebo (p=0.004); the findings were non-significant among those who were overweight or obese. In other words, the greatest risk reduction was seen among those with the lowest BMI, likely because the dose of 2,000 IU vitamin D per day was not enough to significantly increase vitamin D levels among those with a higher BMI.

Other Important Cancer Fighting Co-Nutrients

Don’t forget that vitamin D works along with other essential nutrients for our health. For anti-cancer effects, these include:

Are you getting enough vitamin D and other nutrients to help prevent or reduce cancer?

With almost 90% of the general population having vitamin D levels below the recommended 40-60 ng/ml (100-150 nmol/L), it is obvious that most people need more vitamin D. While most of us cannot achieve a vitamin D level of 40-60 ng/ml from sun alone, either due to our lifestyle, where we live, or other circumstances, we can certainly reach those levels with the right amount of supplementation.

Below is a guide for how much you might need, and who may need more. Your levels can be tested safely at home – order your home test kit today.

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By joining the GrassrootsHealth projects, you are not only contributing valuable information to our study, but you are also gaining knowledge about how you could improve your own health through measuring and tracking your nutrient status, and educating yourself on how to improve it. Do you know what your status of vitamin D, omega-3s, and other essential nutrients is? Could your levels be improved? Test now to find out!

We now have a NEW GIFTING SERVICE that allows you to quickly send ‘Gift Cards’ to friends, family and coworkers who you consider might need immediate access to testing, and to Claim the Joy of Your Health TODAY. Give the gift today!

What does the Research Say about Vitamin D & COVID-19?

It’s TIME to start saving lives! If you can help PREVENT the majority of the death, it’s time! What’s it costing you/us not to take action NOW?

There is much published research that supports a clear link between vitamin D and COVID-19 showing that higher vitamin D levels are related to:

a decreased risk of testing positive for COVID-19

increased viral SARS-CoV-2 RNA clearance

better clinical outcomes among patients with COVID-19

less severe COVID-19 disease

decreased risk of death due to COVID-19

Be sure to educate yourself on the benefits and importance of vitamin D for immune health, and take steps to ensure you and your loved ones are getting enough.

You can review all of the COVID-19 and immune health information we have shared on this page.

Important Message

Help everyone Move Research into Practice with vitamin D and other nutrients! As a special birthday gift to everyone, in honor of the science, we have created a special scholarship fund for anyone to donate to that will go towards helping others participate. Your donation will allow anyone to get help with funding their participation when they need it.

Text-to-give: Text Daction to 44321 to add to our Scholarship Fund.

Donations made through GiveLively are received in full by GrassrootsHealth.

What Does it Take YOU to Get Your D to 40 ng/ml (100 nmol/L)?

Did you know your health could be greatly affected by making sure you have a vitamin D level of at least 40 ng/ml (100 nmol/L)? Help us help you.

STEP 1 - Do you know what your vitamin D level is? If not, be sure to test today to find out.

STEP 2 – Determine your target level. Are you at your target level? Experts recommend a level of at least 40-60 ng/ml (100-150 nmol/L).

STEP 3 – Need to boost your level? Use the D*calculator to see how much vitamin D it may take to reach your target. Opt for the Loading Dose for a quicker boost.

STEP 4 – Optimize how your body absorbs and utilizes vitamin D with co-nutrients and these simple steps.

STEP 5 – Re-Test! This is an important step to make sure you have reached your target level, and to ensure you are not taking too much! Re-testing after 3-4 months is recommended.

STEP 6 – Adjust, Repeat…

Give your immune system the nutrients it needs to support a healthy you and protect yourself from unnecessary diseases, especially COVID-19.


The first Randomized Controlled Trial on vitamin D and COVID-19 has shown a 96% lower risk of ICU admission for those receiving vitamin D (as 25(OH)D to quickly boost vitamin D blood levels) along with the standard treatment, compared to those receiving standard treatment alone.

These results support many previous observational studies showing a relationship between vitamin D levels and intake and COVID-19 severity.

Review the Latest Nutrient Research for COVID-19

GrassrootsHealth Nutrient Research Institute has launched the new Immune Boost project with the use of our myData-myAnswers nutrient health system that nearly 15,000 people are already using for their health. Specific markers that influence immune health are suggested for testing as part of this project including:

  • Vitamin D
  • Omega-3 Index
  • Essential elements magnesium, selenium, and zinc
  • hsCRP

Our goal is to demonstrate how one can use the Nutrient Research Model established by Dr. Robert Heaney to show the effect of vitamin D serum levels of at least 40 ng/ml (100 nmol/L) on risk reduction for all ethnicities in the population. Status and intake of other nutrients will also be analyzed for any type of relationship to immune status and symptom severity. Join the project today!

Please let us know if you're interested in helping sponsor this project.

CLICK HERE for updates and new information about the project.

Through GrassrootsHealth Nutrient Research Institute, you can also test your essential elements magnesium, copper, zinc and selenium, toxins such as lead, mercury and cadmium, as well as your omega-3 levels, inflammation levels and thyroid stimulating hormone (TSH) level. Find out your levels today! Log on to the test selection page (click the link below) to get your tests and see for yourself if your levels can be improved.

Make sure you track your results before and after, about every 6 months!

Click Here to Access the Test Page

How can I track my nutrient intake and levels over time?

To help you track your supplement use and nutrient levels, GrassrootsHealth has created the Personal Health Nutrient Decision System called

For each specific supplement, you can track what days you take it, how much, and many other details.  This will help you know your true supplemental intake and what patterns of use work for you to reach and maintain optimum nutrient levels. Check it out today!