Story at-a-glance

• Recent research claims “high dose” vitamin D supplementation did not result in a lower incidence of cancer or cardiovascular events than placebo
• The “high dose” given in this trial was a mere 2,000 international units (IUs) a day, which is still only a quarter or less of what many need to raise their blood level into a protective range
• The study did not test and track participants’ vitamin D blood levels, which is the only way to ensure sufficiency and adherence to the protocol
• Cancer is a slow-growing disease and effects of nutritional intervention typically only become evident after several years. When the first two years of follow-up data were excluded, people who took 2,000 IUs of vitamin D3 per day had a 25 percent lower risk of cancer in the years following (years three through five)
• Many need upward of 10,000 IUs a day in order to achieve a blood level of 40 ng/mL (100 nmol/L) or higher, which is the bottom cutoff for health and disease prevention. Ideally, you’ll want a level between 60 and 80 ng/mL (150 and 200 nmol/L)

The effectiveness of vitamin D supplementation has again been questioned with negative headlines1,2 trumpeting its failure to prevent cancer and cardiovascular disease. What most researchers and journalists fail to address, however, is the fact that:

• The "high dose" given in this trial was a mere 2,000 international units (IUs) a day, which is still only a quarter or less of what many need to raise their blood level into a protective range
• They did not test and track participants' vitamin D blood levels, which is the only way to ensure sufficiency

Based on those two factors alone, a negative result is precisely what one would predict. Still, despite such limitations, the study actually found some rather remarkable benefits that were simply glossed over.

In fact, had it been a drug trial, vitamin D would likely have been declared a miracle drug against both cancer and cardiovascular disease, based on the findings. This is the kind of perversion of science and selective reporting that shackles public health.

VITAL Study Conclusions

The study3,4 in question, which was in part funded by the U.S. National Institutes of Health, was published in the January 2019 issue of the New England Journal of Medicine (NEJM). (A second study5 compared omega-3 supplementation against placebo for the same endpoints.) As detailed in the vitamin D paper, the study was:

"[A] nationwide, randomized, placebo-controlled trial, with a two-by-two factorial design, of vitamin D3 (cholecalciferol) at a dose of 2000 IU per day6 and marine n−3 (also called omega-3) fatty acids at a dose of 1 gram per day7 for the prevention of cancer and cardiovascular disease among men 50 years of age or older and women 55 years of age or older in the United States.

Primary end points were invasive cancer of any type and major cardiovascular events (a composite of myocardial infarction, stroke or death from cardiovascular causes). Secondary end points included site-specific cancers, death from cancer and additional cardiovascular events."

In conclusion, the authors determined that "Supplementation with vitamin D did not result in a lower incidence of invasive cancer or cardiovascular events than placebo."

What the VITAL Data Actually Reveals

However, as noted by GrassrootsHealth,8 a nonprofit public health research organization dedicated to moving public health messages regarding vitamin D and omega-3 from research into practice, “when the separate types of heart disease or death from cancer were analyzed, there were 30 different very significant results,” summarized in the graph9 below.

Importantly, when the researchers excluded data from the first two years of supplementation, cancer mortality "was significantly lower with vitamin D than with placebo."10

The reason this is important is because cancer is a slow-growing disease and effects of nutritional intervention typically only become evident after several years. It's unreasonable to think you can take a supplement and within weeks or months see a drastic difference in health outcomes. The paper states that clearly, and adds:

"Supplemental vitamin D also did not reduce the occurrence of breast, prostate or colorectal cancers. However, there was a suggestive 17 percent reduction in cancer deaths, which became a 25 percent reduction in analyses that excluded the first two years of follow-up."

Let me repeat those two points for clarity:

1. While incidence of breast, prostate and colorectal cancers were unaffected, those who took a non-ideal dose of vitamin D3 supplements still had a 17 percent lower risk of actually dying from those cancers
2. When the first two years of follow-up data were excluded, people who took a mere 2,000 IUs of vitamin D3 per day had a 25 percent lower risk of cancer in the years following (years three through five)

How is this not good news? Again, let's remember that 2,000 IUs is really insufficient for most people, yet even at this insufficient dosage, the risk of cancer was cut by 25 percent.

For Most, 2,000 IUs a Day Is Suboptimal for Cancer Prevention

In years past, it was widely believed that 4,000 IUs was the upper safe limit, above which you risked vitamin D toxicity, but studies have since refuted this, showing there's no risk of toxicity until you hit 30,000 IUs a day, or a blood level of 200 ng/ml (500 nmol/L).11 Still, the misconception persists.

A significant body of research shows many need upward of 10,000 IUs a day in order to achieve a blood level of 40 ng/mL (100 nmol/L) or higher, which is the bottom cutoff for health and disease prevention. Ideally, you’ll want a level between 60 and 80 ng/mL (150 and 200 nmol/L). This is where the majority of health benefits become really apparent.

As noted in a 2009 study12 on athletic performance and vitamin D, "At levels below 40 to 50 ng/mL the body diverts most or all of the ingested or sun-derived vitamin D to immediate metabolic needs, signifying chronic substrate starvation (deficiency)."

As noted earlier, the VITAL study did not use vitamin D blood levels as the marker for deficiency or sufficiency, and this is perhaps the most significant problem with this study. Blood levels were only measured in a subgroup of 1,644 participants (out of 25,871) after the first year of daily supplementation.

In this group, the mean vitamin D blood level increased from 29.8 ng/mL (74 nmol/L) at baseline to 41.8 ng/mL (104 nmol/L). In other words, most of those taking vitamin D supplements had barely adequate vitamin D levels, and were still significantly short of having ideal blood levels — levels at which research shows the risk of cancer is cut up to 80 percent.

Why You Cannot Trust Studies That Base Results on Dosage Rather Than Blood Measurement

This certainly is not the first time studies have claimed vitamin D supplementation is useless. Last year, a meta-analysis13 concluded once-a-month high-dose vitamin D supplementation had no impact on cancer risk. Here, participants received an initial bolus dose of 200,000 IUs of vitamin D, followed by a monthly dose of 100,000 IUs (so-called pulsed or pulsatile dosing) for a median of three years.

While the media played this up as a finding contradicting recommendations to optimize your vitamin D to lower your cancer risk, it really only made a case against once-a-month mega-dosing. As noted by GrassrootsHealth scientists, for optimal results, you need to supplement frequently (ideally daily) and focus on the achieved serum level, not the dosage.

What's more, 100,000 IUs per month actually only comes out to about 3,000 IUs per day, which again is far below what most adults need to raise their vitamin D serum level into the protective range of 60 to 80 ng/mL, with 40 ng/mL being the low-end cutoff for sufficiency.

Indeed, this analysis noted the mean baseline vitamin D concentration was just over 26 ng/mL, and the mean follow-up level was just 20 ng/mL higher in the supplement group than the placebo group that received no vitamin D.

As in the current NEJM study, participants' vitamin D levels were also not measured regularly throughout the study, and the association with cancer was not analyzed by serum level but by daily dosage.

This point really cannot be stressed enough: The key factor is not how much vitamin D you take but whether or not your blood level of vitamin D is within the "Goldilocks' zone" of 60 to 80 ng/mL, and the only way to ascertain that is through blood testing.

How to Assess Study Quality

GrassrootsHealth scientists have also argued that pulsatile dosing at intervals greater than two weeks may actually cause a form of vitamin D deficiency at the cellular level.

According to GrassrootsHealth, to accurately ascertain the benefit of vitamin D in any given trial, researchers must track not only the baseline and final vitamin D serum level plus the dose given, but also the form (vitamin D2 versus D3) and the dosing interval.

Adherence to protocol is also measured by blood level. If a participant's blood level doesn't change, you know that individual was probably not taking the supplement as instructed, rendering their result null and void.

All of these factors can influence the results, and it's important to get them all right. Identifying the ideal parameters are all part of what GrassrootsHealth is doing. Another study, published in 2017, claimed it found "no case" for vitamin D supplementation during pregnancy.14

In reality, it found seven positive outcomes,15 including increased birth weight, a 40 percent reduction in gestational diabetes, an 18 percent reduction in preeclampsia and a 17 percent reduction in gestational hypertension.

What this study failed to find was a reduction in preterm birth, and this was ultimately translated into headlines that made it appear as though pregnant women have no need for vitamin D supplementation! In reality, nothing could be further from the truth.16,17

So, in summary, when evaluating vitamin D research, the following parameters are what you're looking for in a high-quality study, as without these, the results are likely to be significantly flawed and likely negative:

• Supplementation should be frequent, ideally daily — Bolus doses given at intervals greater than two weeks are likely to be ineffective. According to Carole Baggerly, director and founder of GrassrootsHealth, pulsatile dosing at intervals greater than two weeks may actually cause a form of vitamin D deficiency at the cellular level.

• Dosage, baseline and final vitamin D serum level must all be tracked — Most studies fail in this regard, as most only track dosage and not serum level, which is the most crucial parameter of all.

In short, it doesn't matter how large or small the dose is, as long as it gets the participants into a specific blood level range, as the individual response to any given dose varies widely, depending on several different factors, including intake of other nutrients (such as magnesium), age, ethnicity, body weight and amount of sun exposure.

• The form of vitamin D must be identified — Are they using vitamin D2 or D3? And are they tracking sun exposure, which is the primary way your body produces vitamin D?

There's Strong Evidence Vitamin D Lowers Your Chronic Disease Risk

Vitamin D, a steroid hormone, is vital for the prevention of many chronic diseases, including but not limited to:

• Type 2 diabetes
• Age-related macular degeneration (the leading cause of blindness)
• Alzheimer's disease
• Heart disease
• Well over a dozen different types of cancer, including skin cancer — the very cause of concern that has led so many to avoid the sun exposure necessary for vitamin D production

In the case of heart disease, vitamin D plays a vital role in protecting and repairing damage to your endothelium.18 It also helps trigger production of nitric oxide — which improves blood flow and prevents blood clot formation — and significantly reduces oxidative stress in your vascular system, all of which are important to help prevent the development and/or progression of cardiovascular disease.

Just last year, a Norwegian study19 published in The Journal of Clinical Endocrinology and Metabolism found "a normal intake of vitamin D" significantly reduces your risk of death if you have cardiovascular disease.20

According to vitamin D researcher Dr. Michael Holick, vitamin D deficiency — defined as a level below 20 ng/mL (50 nmol/L) — can also raise your risk of heart attack by 50 percent, and if you have a heart attack while vitamin D deficient, your risk of dying is nearly guaranteed.

Vitamin D also has powerful infection-fighting abilities, making it a useful aid in the treatment of tuberculosis, pneumonia, colds and flu, while maintaining a healthy vitamin D level will typically prevent such infections from taking root in the first place. Studies have also linked higher vitamin D levels with lowered mortality from all causes.21,22,23

A Majority of Breast Cancer Cases Could Be Avoided by Raising Vitamin D Levels Among the General Public

Importantly, the ongoing research by GrassrootsHealth has firmly established that 20 ng/mL, which is conventionally considered the cutoff for sufficiency, is nowhere near sufficient for optimal health and disease prevention.

As mentioned, 40 ng/mL (100 nm/L) appears to be at the low end of optimal, and most participants in the featured NEJM study were likely hovering right around this low-end blood level (based on measurements from a very limited subgroup).

Still, recall the risk of cancer in Years 3 through 5 among those who supplemented with 2,000 IUs a day (thereby reaching a mean blood level of just under 42 ng/mL) went down by 25 percent. GrassrootsHealth research shows the ideal protective range is between 60 and 80 ng/mL (150 to 200 nm/L), and the higher the better within this range.

Research has actually demonstrated that most cancers occur in people with a vitamin D blood level between 10 and 40 ng/mL.24,25 Meanwhile, research shows women with vitamin D levels above 60 ng/mL have an 83 percent lower risk of breast cancer than those with levels below 20 ng/mL.26 Data from GrassrootsHealth ongoing D*Action study actually suggests 80 percent of breast cancer incidences could be prevented simply by optimizing vitamin D and nothing else!

The key, however, is to achieve the proper blood level, which has nothing to do with dosage. And the reason this correlation has never been elucidated before is because no one was using high-enough dosage to actually get participants vitamin D levels above 60 ng/mL, which is where you really start seeing these dramatic reductions in disease.

Optimizing Your Vitamin D Is a Key Disease Prevention Strategy

The evidence in support of vitamin D optimization is overwhelming, and becomes all the more compelling when the blood level is the primary parameter being measured and tracked. The key take-home message here is that 2,000 IUs is insufficient for most people, although it may still cut the risk of cancer by about 25 percent.

Overall, research supports the idea that higher levels offer greater cancer protection, and even levels as high as 100 ng/mL appear safe and beneficial. Importantly, having a serum vitamin D level of 60 ng/mL has been shown to positively impact anyone with breast cancer or Type 1 diabetes, as well as pregnant women and lactating mothers.

It's a shame that so many researchers still have not grasped the importance of measuring blood levels rather than simply going by dosage, and relatively low dosages at that. In reality, what this NEJM study (and others like it) show is that insufficient vitamin D dosage fails to achieve optimal results. It's not that vitamin D itself is useless. GrassrootsHealth D*Action study is clearly leading the pack here, revealing what's required.

It's an ongoing study that relies on public participation, and you can join at any time. To participate, simply purchase the D*Action Measurement Kit and follow the registration instructions included. (Please note that 100 percent of the proceeds from the kits go to fund the research project. I do not charge a single dime as a distributor of the test kits.)

As a participant, you agree to test your vitamin D levels twice a year during a five-year study, and share your health status to demonstrate the public health impact of this nutrient. There is a $65 fee every six months for your sponsorship of this research project, which includes a test kit to be used at home, and electronic reports on your ongoing progress.

You will get a follow up email every six months reminding you "it's time for your next test and health survey." By participating in this project, you help move vitamin D research forward so that, hopefully, one day we can end this nonsensical debate about whether vitamin D optimization is worth pursuing or not.