revised December 18, 2010:

Breast cancer is the most common female cancer in the United States. There are many known risk factors contributing to breast cancer that have emerged from decades of debate and research. Heredity (including the BrCa1 and BrCa2 genes), certain types of diets (high fat and dairy), excess weight, alcohol, and hormone use are well-known proven risk factors. This will address specifically not those issues but the connection between vitamin D insufficiency and breast cancer.

In 2008 the results of a large prospective study were published and did receive a fair amount of publicity. Blood levels of 25-hydroxyvitamin D levels were obtained over six years from 1989 to 1995 from women at the time of the diagnosis of breast cancer. The follow-up on the outcome of the breast cancer occurred over an additional thirteen years. Participants were treated with standard drugs for their breast cancers, but were not treated for their vitamin D insufficiency. This was the first study that looked at how vitamin D levels affected the prognosis of breast cancer.

The results were striking. 24% of women with levels over 30 ng/dl were compared to the 38.5% with levels less than 20 ng/ml. Those with levels over 30 ng/ml were 73% less likely to die and 94% less likely to have their cancer recur during the 10 year period. This study gives us an idea of the potent anti-tumor effect of vitamin D on breast cancer.

It was not an accident that this research started in 1989. In that year the medical journal Lancet published a study showing that activated vitamin D (calcitriol) reduced the growth of breast cancer and killed breast cancer cells in animal research. It was found that women with vitamin D receptor-positive tumors had better prognoses than those with no vitamin D receptors. (Absence of vitamin D receptors in a tumor is an indication of prolonged vitamin D insufficiency). Vitamin D has since been found to have several other beneficial effects in fighting breast cancer cells. An inverse correlation with distance from the equator and breast cancer has also been documented (more sunlight, higher vitamin D levels, less breast cancer). In 2004 a study concluded that vitamin D reduced the number of abnormal mammograms;(many of those abnormalities were premalignant conditions).

Calcitriol is activated vitamin D and a very potent drug that is used in patients on dialysis and in patients who have had their parathyroid glands removed. It can be lifesaving in these conditions, but its major side effect is an elevated calcium level,(hypercalcemia), which can have serious consequences. In the 1990’s pharmaceutical companies tried to find analogues of vitamin D that would retain its ability to fight breast cancer, but at the same time not have the side effect of raising serum calcium levels found in calcitriol. I know this for a fact for three reasons. First, inside sources have reported it; second a close friend of a physician I know took a full-time job as a pharmaceutical researcher around this time for the purpose of discovering vitamin D analogues, and third, at a meeting of the American Society of Clinical Oncology in the mid-1990s I was an observer to a conversation of a very prominent nationally known breast cancer researcher who mentioned that pharmaceutical companies were working on finding vitamin D analogues for cancer prevention and treatment. (Unfortunately I did not understand the significance of this at the time.) The substance with the properties that the pharmaceutical companies were looking for already existed, Vitamin D3. However it is not patentable, therefore potential revenues from Vitamin D3 don’t justify private industry spending money on research and advertising.

There have been several studies since 1989 linking breast cancer incidence with low vitamin D levels. There has been much research showing that breast cancer cells are killed by activated vitamin D (and activated vitamin D increases when the level of vitamin D is sufficient.)

In 2009 there was a study that did receive some initial publicity. A study published in the Journal of the National Institutes of Health gave women only 400 units of vitamin D over many years. 400 units of vitamin D daily is a miniscule dose for an adult and has been shown to raise 25-hydroxyvitamin D levels by only about 5 ng/ml. Previous studies have shown that such a small increase doesn't prevent a significant number of fractures or breast cancer, and this was confirmed in the 2009 study. (Taking 400 units of vitamin D is like throwing a pebble in the ocean). A press release resulted in newspapers reporting the erroneous and dangerously misleading conclusion that “Vitamin D doesn’t prevent breast cancer.” The study showed nothing of the kind; the authors of the study didn’t claim it showed this, and unfortunately an opportunity was lost to spread this vital information about the importance of vitamin D. When an umpire makes a mistake a no-hitter may be lost. But when erroneous misleading press reports about a critical way to prevent breast cancer are published, lives are lost.


1. Have your doctor obtain a 25-hydroxyvitamin D level. Insurance that pays for lab tests should pay for this test just like any other blood test (if the correct diagnosis code is indicated).

2. Obtain a copy of the test results to verify the correct test has been done. (I have seen several instances of 1-25-dihydroxyvitamin D being done instead. This is a different test and is worthless in determining vitamin D sufficiency).

3. Take a vitamin D supplement to obtain vitamin D sufficiency within a few months. The lowest normal level of 25-hydroxyvitamin D is considered 32 ng/ml. 40 ng/ml has been shown to be more beneficial for bone strength and osteoporosis prevention. 52 ng/ml has been shown in a study to have additional benefit for breast cancer prevention. For perspective, it should be noted that male lifeguards in August not taking any vitamin D supplements nor using sun screen have levels of about 100 ng/ml. From sunlight alone, humans cannot attain a level over 150 ng/dl; chemicals in the skin break down at this level so no more vitamin D is produced. It has been documented that no side effects occur from 25-hydroxyvitamin D levels unless the levels are above 150 ng/ml.

4. Vitamin D3 is extremely inexpensive (5000 units daily cost $2 to $4 a month.) (Vegetarian prescription vitamin D2 can be prescribed by a physician for those who prefer). Vitamin D3 is the identical molecule that the human produces in the skin and absorbs in response to sunlight.

5. Levels of 32 ng/ml will lower the incidence of breast cancer. 52 ng/ml has been proven to be better. The evidence indicates that ideal levels are at least 60 to 80 ng/ml and perhaps "lifeguard levels" is what nature intended.

6. Most people are taking far too little vitamin D. Once vitamin D insufficiency is diagnosed, I recommend 5000 units a day with a repeat blood level in six months. In some cases, a higher dose is needed for temporary periods, but this should only be taken with the guidance of blood levels.


1. Follow the above recommendations for preventing breast cancer.

2. Because the situation is more urgent, a repeat blood level should be obtained in 3 months to determine if the dose is high enough.

3. 25-hydroxyvitamin D levels in females who have breast cancer are much lower than the general population. 80% of breast cancer patients have been shown to have low vitamin D levels in a number of studies. (I have tested about 150 breast cancer patients; 100% have had low levels). Levels less than 20/ng/dl are very common in women with breast cancer.

A substantial body of evidence and research dating back to 1989 indicates that vitamin D3 can prevent and treat breast cancer. Oncologists would be quick to point out that there isn’t the perfect long term double-blind control study, Some studies like that may be going on now. However, would you want to be the one that takes a placebo instead of a $2 a month pill that has no side effects and unquestionable lowers the dose of osteoporosis and fractures?


However, does this mean that advanced breast cancer can be simply cured by vitamin D. NO, noone is claiming that. In order for vitamin D to become activated, the cells of the human body converts it to "activated vitamin D."

It has been known for decades that early cancer is more sensitive to chemotherapy agents than advanced cells, presumably because there are more DNA mutations with each multiplication of the cancer cells.

In the same way, there are studies that suggest that advanced cancer produces substances that make it more difficult for 25-hydroxyvitamin D to be converted into activated vitamin D. This would stress even more the importance of health people obtaining an ideal vitamin D level BEFORE cancer deelops. In the future, studies may quantify more exactly the degree of resistance cancer cells have. It would not be surprising if this resistance is not all or none, but gradually increases as the cancer becomes more advanced.

I have seen another issue regarding treatment of breast cancer sometimes causing confusion. Vitamin D is not an antioxidant. Many oncologists advise their chemotherapy patients to refrain from antioxidants such as vitamin C and several of the B vitamins based on some research findings. This has NOTHING to do with Vitamin D.

Common sense may raise the question, “why doesn’t someone just treat breast cancer patients for their low levels of vitamin D to improve bone health?" Some women are already doing this. However it is rare.

Based on projections from studies, some vitamin D research physicians have predicted that if every female in America achieved a 25-hydroxyvitamin D level of even 40 ng./ml, the incidence of breast cancer would plummet 50% within five years.

Twenty-one years have elapsed since the first study linking vitamin D with breast cancer prevention and treatment. The time to take action is long overdue.

It should be noted that the most significant victory to date against breast cancer did not result from a chemotherapy agent, surgery, or radiation. It resulted from the dissemination of knowledge. As soon as it became widely known and publicized in the 1990’s that routine use of hormone replacement was a major risk factor in causing breast cancer, (and most of the reports of the benefits were simply untrue), women simply stopped taking hormone replacement and the incidence of breast cancer dropped 33% within a small number of years. In a similar way, the next significant victory in breast cancer could result in women becoming more proactive and following recommendations regarding achieving an ideal 25-hydroxyvitamin D level.