Published on December 23, 2020

A secondary analysis of the VITAL trial results found a decreased risk of advanced cancer with vitamin D supplementation with normal BMI

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. 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 either male, ages 50 years and older, or female, ages 55 years and older. 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). However, the paper concluded that there was only a possible reduction in fatal cancer with vitamin D supplementation, noting a potential effect modification by body mass index (BMI).

Why is BMI Important to Consider with Vitamin D Research?

Evidence shows that vitamin D levels are greatly affected by obesity. The more fat a person has on their body (the higher the BMI), the more likely they are to have vitamin D deficiency, and their need for vitamin D increases. This is one reason suggesting the same daily intake of vitamin D for all adults simply does not make sense. In fact, the amount of vitamin D needed on a daily basis to achieve a vitamin D level of 40 ng/ml (100 nmol/L) can vary by as much as 3 times the amount, depending on BMI.

In the VITAL trial, vitamin D levels varied significantly by BMI at baseline and after one year of supplementation, and participants in the vitamin D group received only 2,000 IU per day. 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.

Vitamin D Supplementation Analysis by BMI

A secondary analysis of the VITAL randomized clinical trial data by Chandler et al. was completed to determine the effect of daily 2,000 IU vitamin D supplementation on the development of advanced, metastatic cancer and cancer death with BMI (grouped as below 25, 25 to under 30, and above 30) included to see if it modified the effects of supplementation.

A total of 1,617 participants were diagnosed with invasive cancer, with an average follow up time of 5.3 years. Supplementation with vitamin D did reduce the incidence of metastatic or fatal cancer in the overall cohort. Of those diagnosed, 226 (1.7%) had been receiving vitamin D and 274 (2.1%) had been receiving a placebo. Overall, there was a 17% reduced risk of metastatic or fatal cancer among the vitamin D group versus the placebo group (p=0.02).

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When taking BMI into consideration 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.

Making Conclusions Based on Vitamin D Level, Not Intake

Due to the large range of variability in the response to a particular dose, vitamin D testing should be used to personalize the intake amount. Therefore, the above conclusion leaves us to ponder, since BMI is a major factor affecting the dose response of vitamin D, what would an analysis by vitamin D level instead of intake have shown us?

The following are some of the guidelines from Dr. Robert Heaney’s Guidelines for optimizing design and analysis of clinical studies of nutrient effects:

  1. Basal Nutrient status must be measured, used as an inclusion criterion for entry into study, and recorded in the report of the trial.
  2. The intervention (i.e., change in nutrient exposure or intake) must be large enough to change nutrient status and must be quantified by suitable analyses.
  3. The change in nutrient status produced in those enrolled in the trials must be measured and recorded in the report of the trial.
  4. The hypothesis to be tested must be that a change in nutrient status (not just a change in intake) produces the sought-for effect.
  5. Co-nutrient status must be optimized in order to ensure that the test nutrient is the only nutrition-related, limiting factor in the response.

While the conclusions from the VITAL study based on intake are promising, the optimal methodology for making such conclusions would have been to look at the results based on vitamin D levels at the start of the study and after supplementation. This would show what effect supplementation had on the serum level, and if it raised the level enough to make a difference for the outcome being measured.

Since many factors affect the dose response to supplementation (including BMI and various co-nutrients such as magnesium), testing is absolutely essential. Without this information, it is difficult to make a solid conclusion about the effect of vitamin D on any particular health outcome.

Don’t Blindly Supplement – Test Your Vitamin D Level Today!

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.

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!