Scientific Link Between Vitamin D Deficiency And Cancer

Vitamin D Deficiency and Cancer

Dermatologists have successfully hammered one thought into all of us: sun exposure may cause skin cancer, so wear sunscreen while you’re out in the sun. What dermatologists don’t tell us is that the vitamin D we get from sunshine can also prevent serious cancers such as breast, colon, pancreatic and prostate cancers.

Mounting scientific evidence shows a strong link between vitamin D deficiency and cancer. Wouldn’t it be wonderful if we could prevent cancer by optimizing vitamin D level in the body?  Even in patients with a diagnosis of cancer, proper vitamin D supplementation plays an important role in treating cancer and preventing its recurrence.

What promotes cancer growth?

In the last two decades, research has clearly shown two factors can promote growth of cancer:  Vitamin D deficiency and Insulin Resistance Syndrome.

First, let’s examine how cancer develops. In your body, old cells are constantly dying and fresh new cells are being born. In other words, there is a continuing cycle of death and birth of cells. There is also a fine balance between the death and the birth of cells.

Vitamin D is involved in the death of cells and insulin is involved in the growth of new cells. Now consider a scenario where vitamin D is low in the body and insulin level is high. Both of these factors cause a shift in the normal balance of the death and birth of cells.  Low vitamin D causes a decrease in the death of cells and a high insulin level causes an increase in the growth of cells. The net result is an enormous increase in the number of cells. This is exactly what happens when you have cancer; an unlimited growth of abnormal cells in your body.

A high level of insulin is present in people with Insulin Resistance Syndrome (also known as Metabolic Syndrome).  Briefly, Insulin Resistance Syndrome consists of obesity, hypertension, low HDL cholesterol, high triglycerides, pre-diabetes or diabetes, polycystic ovary syndrome and high uric acid level. You don’t have to have all of these features. Just a couple of them are enough to have a diagnosis of Insulin Resistance Syndrome. Some complications of Insulin Resistance Syndrome include: coronary artery disease, stroke and fatty liver.  For an in depth look at Insulin Resistance Syndrome, please read my book, “Take Charge of Your Diabetes.”

We could call Vitamin D deficiency and high insulin two important promoters of cancer. It’s interesting to note that Vitamin D deficiency has been shown to worsen Insulin Resistance Syndrome which results in a further increase in insulin level.

In addition, obesity, which often plays a central role in Insulin Resistance Syndrome, also causes vitamin D deficiency. Obesity is the obvious common denominator for insulin resistance and vitamin D deficiency. For a long time, physicians have known obesity to be a strong risk factor for cancer. Now we understand that Vitamin D deficiency and insulin resistance are two pathways for how obesity is linked to cancer.

Both vitamin D deficiency and Insulin Resistance Syndrome have reached epidemic proportions, affecting hundreds of millions of people around the world. What’s alarming is that both vitamin D deficiency and Insulin Resistance Syndrome are getting worse. It is intuitive to predict that we will continue to see increasingly large numbers of cancer cases as time passes.

Can Vitamin D help in the treatment of cancer?

The answer is yes!

Vitamin D not only helps to prevent cancer, but it also helps in the treatment of cancer. A researcher from Harvard Medical School published an excellent article (3) in 2005 citing the enormous evidence which strongly supports the anti-cancer role of vitamin D supplementation in patients with colon cancer.

In the case of breast cancer, the role of vitamin D as an anticancer agent is promising. In the case of prostate cancer, it appears that the more active form of vitamin D, known as 1,25, (OH)2 vitamin D, provides anti-cancer activity.

Amazingly, many oncologists don’t seriously consider the great anti-cancer benefits of vitamin D. Some oncologists who stay updated on current knowledge may casually recommend vitamin D to their patients.

What I’ve seen in my patients is usually something like this:  If a patient brings up the subject of vitamin D, the oncologist might say, “Yeah, it’s a good idea. You should take vitamin D.” Unfortunately, that’s often the end of the advice. Vitamin D level is not checked. Dosage amount is not discussed.  The patient usually ends up taking vitamin D on their own at dose of 400 I.U. per day, which according to the bottle label, meets 100% of the daily recommended dose.  When these patients come to see me for some other reason, such as diabetes, I check their vitamin D level.  In most cases, their vitamin D level is low, despite being on the recommended dose of 400 I.U per day.

So beware and take charge of your vitamin D status and supplementation!


  1. Garland CF, Garland FC, Gorham ED et al. The role of vitamin D in cancer prevention. Am J Pub Health.2006;96(2):252-26.
  2. Tretli S, Hernes E, Berg JP, et al. Association Between serum 25(OH)D and death from prostate cancer. Br J Cancer.2009;100(3):450-454.
  3. Giovannucci E. The epidemiology of vitamin D and cancer incidence and mortality: a review( United States). Cancer Causes Control.2005;16(2):83-95.

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