New Research on Vitamin D and Breast Cancer: What It Means for Women’s Health

Dr. Stengler: In this video, I'm going to walk you through what the latest research shows for vitamin D in women receiving treatments for breast cancer and how to best use vitamin D to your advantage. I'm Dr. Mark Stengler, and I've researched and written 20 books on nutrition and functional medicine, and I've been practicing integrative medicine as a naturopathic medical doctor for 30 years.

Many of you are aware that vitamin D has so many powerful effects in the body — it helps with bone health and inflammation. But we're going to talk about how it really affects cancer, and some recent research on it. The study I'm referring to is titled "Vitamin D Supplementation Improves Pathological Complete Response in Breast Cancer Patients Undergoing Neoadjuvant Chemotherapy: A Randomized Clinical Trial," published in the journal Nutrition and Cancer — so, very mainstream.

In the study, they compared vitamin D to placebo in women ages 45 and older who had breast cancer and were getting chemotherapy to reduce the tumor size so they could go on to other treatments, like surgery. The women were split into two groups. The vitamin D group took a daily supplement of 2,000 IU of vitamin D for six months. The placebo group took a pill that looked the same but had no vitamin D, also for six months. Research has shown that women with breast cancer often have vitamin D deficiency at the time of diagnosis, and in this study, women in both groups had vitamin D deficiency at the start.

What they looked at was the pathological complete response rate, or PCR. This is a huge deal because it's an important prognostic factor in breast cancer and is linked to a better outlook. It's when, after chemotherapy and surgery, the pathologist finds no signs of remaining invasive cancer in the breast tissue or lymph nodes. After six months, the results were quite striking. The women who took the daily vitamin D supplement — only 2,000 units, not a high dose in my opinion — had a much higher PCR rate: 43% achieved a complete response, compared to only 24% in the placebo group. The researchers also found that women with vitamin D blood levels greater than or equal to 20 nanograms per milliliter at the end of the intervention were more likely to achieve PCR than those with a deficiency. In fact, the higher the vitamin D level, the higher the percentage of women who achieved PCR, demonstrating a positive association.

How does vitamin D help? Vitamin D is thought to play a protective role in the development of breast cancer. It's converted into its active form within the tissue, including the breast tissue itself. The active form interacts with the vitamin D receptor and can help slow down the cancer cell's ability to grow, multiply, and spread. Vitamin D also acts as a chemo booster — it appears to influence the response to chemotherapy agents, consistent with experimental studies demonstrating that vitamin D sensitizes breast cancer cells to chemotherapy and enhances the anti-tumor activities of common chemotherapy agents.

Why does this matter? It seems to be quite beneficial for women getting cancer treatments to take vitamin D. These results reinforce the theory that increasing serum vitamin D through supplementation increases the levels in the target tissue, such as breast tissue, producing that active form. Vitamin D is very inexpensive, especially compared to pharmaceutical medications. The results agree with scientific evidence showing an association between vitamin D deficiency and the prognosis and mortality of breast cancer. If you or a loved one are on a breast cancer journey, these findings reinforce the importance of assessing your blood vitamin D levels and supplementing when your levels are deficient or suboptimal. Talk to your doctor about having your vitamin D levels checked — it's a small step that can make a big difference in your outcome. I routinely do this not just for patients with cancer, but for all my patients, because vitamin D deficiency or suboptimal levels are so common.

In our book Outside the Box Cancer Therapies, Dr. Anderson and I document that several population studies suggested vitamin D deficiency increased the risk of adults developing cancer. In a study of 790 female breast cancer survivors, 75.6% had low blood vitamin D levels. A review of studies found that postmenopausal women with low vitamin D levels had a higher risk of developing breast cancer compared to those with high levels. In women with a history of breast cancer, vitamin D status has been strongly associated with better survival. Research suggests that a blood level of 25-hydroxy vitamin D should be at least 40 nanograms per milliliter; most labs show the range between 30 and 100, and you need a level like this to reduce your risk of developing cancer.

This study used 2,000 units of vitamin D, equivalent to 50 micrograms. I have most patients take 5,000 IU, equivalent to 125 micrograms. I test the patient's blood levels, give them vitamin D supplementation, and increase the levels if they're not at an optimal level above 40 — we usually shoot for mid-range. I always have patients supplement K2 with vitamin D when it's used long-term, because K2 directs the calcium to your bones and away from your arteries, and vitamin D enhances the absorption of calcium into your bloodstream. A lot of people don't get vitamin D readily because it's in foods many people don't eat regularly — salmon, herring, sardines, cod liver oil, a little in butter and egg yolks, and shiitake mushrooms left out in sunlight — but the amounts aren't very high. You also get vitamin D when your skin is exposed to sunlight. However, women with breast cancer receiving chemotherapy are often on agents that make the skin sun-sensitive, so they're advised to stay out of the sun or use sunscreen, which makes them prone to vitamin D deficiency.

I'm not sure why so many oncologists, given all the research we've had on vitamin D in the last decade, aren't routinely testing patients' vitamin D levels. I have so many patients who come in for integrative cancer support, and I'm the first one to check their vitamin D levels — and quite often we find they are deficient or low. It's something that should have been screened long ago. I hope you liked this video. Hit the like button, hit the subscribe button, and I look forward to reaching out to you with other videos in the near future.

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