Breast Cancer and Vitamin D-What You Need To Know

As we enjoy the summer solstice, most of us are spending more time outside absorbing the sunlight, and enjoying the longer days. The sun provides us with soothing warmth, energy, and can make us feel more optimistic about life in general.

Another wonderful thing that the sun offers, which we are probably less likely to be thinking about as we’re soaking up the rays, is vitamin D.

You may have heard of vitamin D as a supplement to support bone health, seen it in the stores or in your multivitamin, or heard someone say that you can get it from the sun. However, many people don’t realize just how important vitamin D is in supporting the functions of our bodies. Not only does it promote the absorption of calcium and phosphorus in bone mineralization, growth, and repair, it also supports immune health.

Perhaps most importantly for you now, studies are clearly showing that it plays an important role in breast cancer prevention and treatment.1, 2 Vitamin D can support breast cancer treatments and improve outcomes. In a number of studies, it has been shown to inhibit cancer cell reproduction and induce cancer cell death, through its effect on the expression of proteins that regulate the cell cycle, as well as two pathways -the insulin-like growth factor I (IGF-I) and estrogen-receptor (ER) - involved in breast cancer cell promotion.2, 3 Also of importance, it has been found that when combined with radiation, vitamin D is capable of destroying radiation-resistant cells.3, 4, 5 

What is Vitamin D?

This might come as a surprise, but vitamin D is actually not really a vitamin at all. Rather, it’s a type of hormone molecule with a chemical structure similar to cholesterol, that helps regulate at least 3,000 genetic functions in the body. There are two forms of vitamin D utilized in the human body - D2 (ergocalciferol) and D3 (cholecalciferol) - which are precursors to what we collectively call “vitamin D”.

We get most of our vitamin D from exposure to sunlight, through our skin. Specific ultraviolet rays from the sun penetrate the skin, where they are converted from a precursor naturally contained within the skin, into vitamin D. The vitamin D then works its way through the body’s metabolic system (a set of chemical reactions that maintains cell life), through the liver and kidneys, where it is converted to calcitriol, the active form of vitamin D.

But largely due to changes in our culture over the last century, people are getting less direct sunlight than in decades before. Technology advances have led people to spend much more time indoors as well as a rising awareness of the sun’s potential harmful effects on the skin are contributing to an increase in vitamin D deficiency. This is especially true for people who reside in the northern hemisphere, and tend to have less exposure to the sun during the winter months. Lastly, women who are receiving chemotherapy, and especially during radiation treatment, are told to avoid exposure to the sun.

The Role of Vitamin D in Breast Cancer

Vitamin D deficiency has been found in 96% of newly diagnosed breast cancer patients, so it’s clear that there is a connection between vitamin D levels and breast cancer risk.6 Studies are also revealing that the prognosis of various types of cancer, including breast cancer, may be correlated with vitamin D levels at the time of diagnosis and during treatment.4,7

The active form of vitamin D, cholecalciferol, has been found to be a potent anti-cancer agent. It was previously believed to be made only in the kidneys, but researchers have recently determined that the enzyme that activates vitamin D is increased in tumors. One theory suggests that having the ability to make vitamin D is part of the breast’s natural immune response to tumors.8

Testing for Vitamin D 

Mostly due to our indoor lifestyle, it’s very common to have vitamin D deficiency. I’ve had women in my practice with levels as low as 12ng/mL; so I always include vitamin D testing as part of my comprehensive initial intake workup.

Vitamin D levels are easily measured through a blood test and the most accurate way to check your vitamin D levels is to test for 25-hydroxyvitamin D [25(OH)D]. Serum 25OHD comprises the sum of 25OHD2 and 25OHD3. Because of the widespread use of both vitamin D2 and vitamin D3 in the United States and Canada, analysts must measure both 25OHD2 and 25OHD3 in order to provide the total 25OHD level in serum.

This test requires a blood draw from a qualified lab and can be ordered by your practitioner. Many labs also now have patient portals available online, where you can view the results yourself as soon as they are completed and uploaded.

However, if your practitioner does not feel it necessary for you to know your vitamin D level, as part of your Empowerment (remember the 3 Pillars of Energy, Empowerment and Grace), you can order this directly through

In my clinical practice, I like to see a range for women between 50 ng/mL (nanograms/milliliter) to 65 ng/mL.

Ulta Lab Tests

Supplementing with Vitamin D

Supplementation with vitamin D is recommended if your vitamin D level is below 45ng/mL or if you are one of the many people who have trouble converting vitamin D into the active form.

Of the two types of vitamin D, D3 is the preferred form for supplementation, as it is superior in its ability to raise and sustain the blood and tissue level of 25-hydroxyvitamin D. While vitamin D3 supplements are available over the counter at any pharmacy, drugstore, or supermarket, it’s important to consider the dose you need, and the source, before purchasing just any supplement.

Vitamin D3 supplements are dosed in IUs (International Units). Oftentimes, people may be inclined to take high doses such as 10,000-50,000 IUs, either for therapeutic effect or to correct a deficiency, but I disagree with that approach. First, there is no such thing as such a high dose of vitamin D from nature. Even if you spend an entire day in the sun, you wouldn’t receive that amount of vitamin D.

Secondly, Vitamin D is a fat soluble substance, meaning it is absorbed along with the fats we eat, and can be stored in our body fat. This makes it much more difficult for the body to get rid of excess vitamin D, and if too much builds up it can lead to toxicity.

For most people, a serving of 5,000 IUs once daily is safe and helpful, and aligns with what we might naturally obtain.

There are thousands of over the counter options for vitamin D3 supplementation, but just as important as taking the right dose, is finding the right supplement. Sadly, supplement companies are not regulated in the same way that pharmaceutical companies are. This means that the quality, safety, and efficacy of supplements can vary vastly across brands.

I recommend looking for professional, name brands that use strict quality control and independent testing to ascertain there are no toxins or harmful fillers in their products, and that the ingredients listed on the bottle are consistent with each batch produced. Designs For Health is one reputable brand with an excellent vitamin D supplement that I use in my practice. They have both a liquid, Emulsi D3 Synergy, and a small capsule option, Vitamin D Supreme!

Vitamin D in Food

Aside from sunshine and supplementing, vitamin D can also be obtained through the foods we eat. Healing foods that are high in vitamin D include: fatty fish, such as salmon and tuna, beef liver, and egg yolks. Dairy products like cheese, yogurt, and cow’s milk also contain some vitamin D, but I generally do not recommend these foods during the healing process.

Although incorporating more healing foods into your diet is a wonderful way to support vitamin D levels, it may not be the most effective option, especially in the case of a true deficiency. It would be very difficult to carefully track and ensure an adequate intake on a daily basis. As such, supplementing is a more reliable complement to your diet and health.

A Note About Sunscreen

The sun can be an amazing source of healing energy; the sun rays that the skin uses to produce vitamin D - may help to reduce the risk of breast cancer. However, the potential dangers to your skin are real.

As you proceed into the summer months, should you decide to enhance your vitamin D intake through absorbing more of the sun’s revitalizing rays, it’s also important to be cautious about the type of skin protection you are using.

Unfortunately, the most common and convenient way to protect your skin from the sun is sunscreen, and Over The Counter (OTC) sunscreens have some dangers of their own.

Sunscreens are used to protect the skin from ultraviolet (UVA) and waveband exposure, but the effectiveness of sunscreens can be reduced and the ultraviolet exposure not blocked because they are improperly or inadequately applied.

Everything we put on our skin is absorbed into our bodies, and standard sunscreens contain toxic endocrine disrupting ingredients, such as oxybenzone, octinoxate, and homosalate. These ingredients can impact the activity of estrogen and other hormones, and can promote breast cancer cell growth.

Instead of using commercial sunscreens that contain these toxins, I recommend limiting your sun exposure between 10am and 4pm, and I have the perfect sunscreen for you to use!

3rd Rock Sunblock is owned by my friend and colleague, Guerry Grune. This sunblock contains ingredients formulated around zinc oxide complex, which is the world’s best UV blocker, and actually protects skin cells by strengthening cell walls. Unlike OTC products, the wonderful smell is obtained through essential oils, which act to strengthen the skin’s immune response to repel infections and carcinogens. And there are no endocrine disruptors in this sunblock! Every ingredient in this sunscreen is food grade edible, non-GMO and non-toxic!

It doesn’t get any cleaner than this!

You can purchase this here, and as members of my community, you’ll receive 20% off with the code: THEPATH.


  1. Lowe L, Hansen CM, Senaratne S, Colston KW. Mechanisms implicated in the growth regulatory effects of vitamin D compounds in breast cancer cells. Recent Results Cancer Res. 2003;164:99-110. Department of Cellular and Molecular Medicine, St. George's Hospital Medical School, Cranmer Terrace, London SW17 ORE, UK.
  2. O'Kelly J, Koeffler HP., Vitamin D analogs and breast cancer. Recent Results Cancer Res. 2003;164:333-48. Division of Hematology/Oncology, Cedars Sinai Medical Center, UCLA School of Medicine, 8700 Beverly Boulevard, Los Angeles, CA 90048, USA. [email protected]
  3. Banerjee P, Chatterjee M. Antiproliferative role of vitamin D and its analogs–a brief overview. Mol Cell Biochem. 2003 Nov;253(1-2):247-54.;51(5):415-21
  4. Robsahm TE.  Tretli S. Dahlback A.  Moan J. T.E. Robsahm, Cancer Registry of Norway, Inst. of Pop.-Based Cancer Research, Montebello, 0310 Oslo; Norway.  E-Mail: [email protected] Vitamin D3 from sunlight may improve the prognosis of breast-, colon- and prostate cancer (Norway).Cancer Causes & Control. Vol. 15(2)(pp 149-158), 2004.
  5. Sundaram S, Gewirtz DA. The vitamin D3 analog EB 1089 enhances the response of human breast tumor cells to radiation. Radiat Res. 1999 Nov;152(5):479-86.
  6. Imtiaz S, Siddiqui N, Raza SA, Loya A, Muhammad A. Vitamin D deficiency in newly diagnosed breast cancer patients. Indian J Endocrinol Metab. 2012 May;16(3):409-13. doi: 10.4103/2230-8210.95684.
  7. Lim HS, Roychoudhuri R, Peto J, Schwartz G, Baade P, Moller H.  Cancer survival is dependent on season of diagnosis and sunlight exposure. Int J Cancer. 2006 May 2
  8. Townsend, K. Hewison, Martin, Boosting Vitamin D Levels May Help Prevent Breast Cancer, Study Suggests, 23rd Joint Meeting of the British Endocrine Societies with the European Federation of Endocrine Societies, March 22-24, 2004, University of Birmingham and St. George's Hospital, London