This seasonal deficiency endangering your health

Plus, the life-saving ways you can fix this shockingly common problem

Recently, I came across a brand new study concluding that the U.S. government’s standard recommendation for vitamin D isn’t high enough to protect against colorectal cancer.

To be frank, that’s nowhere close to what I’d consider to be new, groundbreaking research…

I’ve been telling you for years that the recommended daily allowance (RDA) for vitamin D is woefully inadequate. And it’s not just my opinion. Reams of research show that the 600 IU RDA for adults under age 70 (800 IU for those over 70) may be adequate for bone health, but not much else.

Instead, researchers have found that the optimal dose is over 10 times higher—10,000 IU of vitamin D3 a day. This not only helps protect your bones, but it’s also been shown to substantially lower your risk of cancer, heart disease, lung disease, Alzheimer’s disease, multiple sclerosis, depression, and more.

In fact, if you took just one supplement a day, I’d tell you to take vitamin D3. That’s how crucial this nutrient is for all aspects of your health. But sadly, the Vitamin D Council reports that a whopping 70 percent of the U.S. population is deficient in this essential vitamin.1

Autumn’s onset makes D more crucial

Getting enough D is particularly important as summer ends, days shorten, and the sun sits lower in the sky. From October to March, the sun’s rays don’t penetrate the atmosphere enough to allow all people who live in the Northern Hemisphere to make adequate amounts of vitamin D.

And that’s not the only reason for D deficiency. In a moment, I’ll tell you some surprising factors that can affect how your body makes and absorbs vitamin D.

But first, let’s take a closer look at the new study on colorectal cancer I mentioned earlier, plus two other key studies on vitamin D’s effect on ovarian cancer, and on lung disease.

What leading cancer researchers reveal about D

In June, the Journal of the National Cancer Institute reported findings from scientists at the American Cancer Society, the Harvard School of Public Health, the National Cancer Institute (NCI), and other reputable organizations about the significant association between higher vitamin D levels and lower risk of colorectal cancer.2

This international analysis looked at 17 studies involving 5,700 people with colorectal cancer and 7,100 people without it.

Just as I did when I conducted studies at NCI (with some of the same folks who led this new study), the researchers used the same analytical equipment, calibrations, standards of measurement, and units of measure to evaluate blood samples from each study participant.

So even though they were dealing with a broad range of people from around the world, there was no question the researchers were consistently measuring vitamin D levels across the board.

After five years, the researchers found that the study participants with low vitamin D levels had a 31 percent higher risk of developing colorectal cancer compared to those with “sufficient” levels (the 600 IU RDA, or 30 nmol/L of vitamin D in their blood).

Meanwhile, the people with higher D levels (75 to 100 nmol/L) had a 22 percent lower risk of developing colon cancer. And for every D increase of 25 nmol/L, women’s risk of colorectal cancer decreased by 19 percent, and men’s fell by 7 percent.

In other words, you need at least three times the RDA of vitamin D to lower your risk of colorectal cancer. And the more D you get, the more your risk plummets.

Meanwhile, another new study from the Journal of the NCI found that the active form of vitamin D (calcitriol, which your body makes from vitamin D3) improves survival in women with deadly ovarian cancer.3 

The research was highly technical, but the upshot is that vitamin D3 helps your normal cells fight cancer cells.

A daily dose can help you breathe easy

In another new study, scientists at Johns Hopkins University analyzed data collected from about 6,300 men and women, with an average age of 62, over a period of 10 years.

The researchers found that lower levels of D were associated with a higher risk of lung disease.4

Specifically, people who had vitamin D levels of less than 20 nmol/L had a greater risk of interstitial lung disease (ILD)—a form of lung inflammation and scarring caused by asbestos, coal dust, autoimmune disorders, infections, and side effects of prescription drugs. This disease is so brutal that most people don’t live more than five years past their diagnosis.

The researchers said vitamin D has key hormonal activity that helps regulate the immune system and act against chronic inflammation—like the kind associated with ILD.

They also noted that vitamin D plays an important role in asthma and COPD prevention. And in my view, it’s most likely through the same mechanism.

Four reasons why you’re D deficient

As I mentioned earlier, we’re entering a time of year when most of us aren’t able to make enough vitamin D from the sun alone. But there are other specific factors that can wreak havoc on your vitamin D levels.

1) You’re not taking the right form of D. Many people don’t realize there are different types of vitamin D. For example, vitamin D2 is not as bioavailable as D3—meaning you absorb less of it in your GI tract. And efficient absorption is crucial, since this is how nutrients enter your bloodstream.

But recent findings show that vitamin D3 immediately gets to work with the probiotics (“good” bacteria) in your GI microbiome—before it even enters your bloodstream. And as I’ve reported many times before, the healthier your gut bacteria, the better your overall health.

2) You’re on a low-fat diet. Vitamin D is only absorbed properly when it’s combined with some fat. So following a ridiculously unhealthy “low-fat” diet—which typically consists of low protein and high carbs—means you may not be absorbing enough fat-soluble vitamins like D.

Also, supplements with vitamin D3 must contain some healthy fat right in the capsule. That’s yet another reason why multivitamins are so useless—they don’t contain the proper nutrients (like fats) to help you absorb the vitamin and mineral content.

The fact is, you simply can’t get every nutrient you need in one little pill. Instead, decide what supplements are right for you and get the proper formulations from sources you trust.

3) You have certain medical conditions. As I mentioned earlier, it’s crucial for your GI tract to properly absorb vitamin D. But liver diseases, kidney diseases, celiac disease, Crohn’s disease, and cystic fibrosis can hinder this absorption.

That’s why it’s a good idea when you go in for your next check-up to ask your doctor for a standard blood test to identify any red flags or markers for these diseases.

Obesity can also interfere with vitamin D absorption. That’s because extra fatty tissue sucks up D, preventing it from going where it’s needed in the body. But gastric bypass surgery—a common treatment for obesity—can result in a lifetime of poor absorption of vitamin D (along with many other nutrients).

That’s why I recommend cutting both sugar and processed carbs from your diet. It can help your waistline shrink and your vitamin D blood levels improve—without having to undergo costly and potentially dangerous weight-loss surgery.

4) You’re taking statins or other prescription drugs. Taking a cholesterol-lowering statin drug can prevent you from achieving optimal vitamin D levels, even with supplementation and sun exposure.

Why? Because vitamin D acts like a hormone in the body, and hormones rely on cholesterol as a basic building block. So artificially lowering your cholesterol prevents the absorption of many important nutrients (like vitamin K2 and Coenzyme Q10).

And, as I’ve mentioned many times before, lower cholesterol doesn’t prevent heart disease—but vitamin D does. So, essentially, statins are a double whammy. They don’t reduce your risk of heart disease, but they hinder the absorption of vitamin D, which can indeed lower that risk.

Meanwhile, prescription drugs that contain calcitroic acid can transform vitamin D into its inactive form. These most commonly include anticonvulsants, steroids, antiviral medications, and anti-immune drugs for preventing tissue rejection (typically following an organ transplant).

The simple steps you can take to deliver the D

The first step in determining whether or not you’re getting enough vitamin D is to ask your doctor to check your blood levels twice a year—once toward the end of winter and again toward the end of summer. All you need is a simple blood test called the 25-hydroxy vitamin D, or 25(OH)D test.

Optimal vitamin D blood levels are between 50 and 75 nmol/L—although as we saw with the colorectal cancer study I mentioned on page 5, as much as 100 nmol/L can help protect you against disease.

So if your D levels are low, don’t fret. You can build them up by supplementing with 10,000 IU of vitamin D3 a day. I like to combine the convenient, highly absorbable liquid form of D3 with the potent marine carotenoid astaxanthin for added benefits.

For more information on astaxanthin or the latest vitamin D research (and seven years’ worth of archived information), just head to my website, And if you have any questions in particular, please feel free to send me an email at


1Are we currently amid a vitamin D deficiency pandemic?” Vitamin D Council. 18 November 2016. Retrieved from:

2“Circulating Vitamin D and Colorectal Cancer Risk: An International Pooling Project of 17 Cohorts.” JNCI: Journal of the National Cancer Institute, djy087.

3“Systematic Identification of Druggable Epithelial–Stromal Crosstalk Signaling Networks in Ovarian Cancer.” JNCI: Journal of the National Cancer Institute, djy097.

4“Serum 25-Hydroxyvitamin D Concentrations Are Associated with Computed Tomography Markers of Subclinical Interstitial Lung Disease among Community-Dwelling Adults in the Multi-Ethnic Study of Atherosclerosis (MESA), The Journal of Nutrition, Volume 148, Issue 7, 1 July 2018, Pages 1126–1134.