Vitamin D is a fat-soluble vitamin that plays an important role in the battle against breast cancer.
Humans get vitamin D from animal foods like beef, eggs, liver, and salmon,1 and mushrooms are really the only meaningful non-animal source of naturally occurring vitamin D.2 In addition, some foods like milk and orange juice are commonly fortified with vitamin D.1
The human body also makes vitamin D. Vitamin D synthesis starts in the skin when sunlight interacts with 7-dehydrocholesterol to form cholecalciferol (and yes, sunscreen interferes with this process). Cholecalciferol is then converted in the liver to 25-hydroxycholecalciferol, which is then converted in the kidney to 1,25-dihydroxycholecalciferol.1,3 The molecule “1,25-dihydroxycholecalciferol” is the good stuff. It’s what we care about, it’s what does the job of vitamin D, and it’s what most people mean when they say vitamin D.
Vitamin D has many important functions in the body. It regulates serum levels of calcium and phosphorus, it promotes bone mineralization, it modulates immune function, and it regulates cell growth and differentiation.1,3
It has been estimated that 40% of the general population in the United States is deficient in vitamin D,4 and, among women diagnosed with breast cancer, deficiency appears to be even more common.5 Indeed, vitamin D deficiency actually increases the risk of developing breast cancer.6,7
Ensuring your vitamin D levels are adequate is an easy step to take to reduce your risk of developing breast cancer in the first place. If you’ve already been diagnosed with breast cancer, it’s equally important to ensure you have an adequate level of vitamin D. Preliminary evidence suggests vitamin D may enhance the effectiveness of standard treatments like chemotherapy and radiation,8,9 and sufficient levels of vitamin D may reduce breast cancer mortality.10
Whether for breast cancer prevention or treatment, it is worthwhile to make sure your vitamin D levels are adequate. It is possible to test vitamin D levels in your body. For accurate results, you’ll want to make sure your provider tests your level of 25-hydroxycholecalciferol specifically.11 Based on your test results, you can supplement with an appropriate dose of vitamin D (often ranging from 500 to 5,000 IU per day and taken at or before noon). You’re looking for your level to be in the range of 30–80 ng/mL,10 though there might be some added benefit of getting that number closer to 60 ng/mL.7
As always, consultation with a professional who is knowledgeable in natural medicine is important since vitamin D supplementation may interfere with some prescription medications,12 may be harmful in relation to other diseases,13 and may require supplementation of additional nutrients.14
Be sure to talk with your healthcare provider about vitamin D and breast cancer.
Visit www.NaturalMedicineAdvisors.com to learn more.
 Gropper SS, Smith JL, Groff JL. Advanced nutrition and human metabolism. 5th ed. Belmont CA: Wadsworth, Cengage Learning; 2008.
 Cardwell G, Bornman JF, James AP, Black LJ. A review of mushrooms as a potential source of dietary vitamin D. Nutrients. 2018;10(10):1498.
 Haas EM, Levin B. Staying healthy with nutrition medicine. 21st century edition. Berkeley, CA: Celestial Arts; 2006.
 Parva NR, Tadepalli S, Singh P, Qian A, Joshi R, Kandala H, et al. Prevalence of vitamin D deficiency and associated risk factors in the US population (2011-2012). Cureus [Internet]. 2018; Available from: http://dx.doi.org/10.7759/cureus.2741.
 Voutsadakis, IA. Vitamin D baseline levels at diagnosis of breast cancer: A systematic review and meta-analysis. Hematol Oncol Stem Cell Ther. 2020; article in press.
 Yin L, Grandi N, Raum E, Haug U, Arndt V, Brenner H. Meta-analysis: Serum vitamin D and breast cancer risk. Eur J Cancer. 2010;46(12):2196–205.
 McDonnell SL, Baggerly CA, French CB, Baggerly LL, Garland CF, Gorham ED, et al. Breast cancer risk markedly lower with serum 25-hydroxyvitamin D concentrations ≥60 vs <20 ng/ml (150 vs 50 nmol/L): Pooled analysis of two randomized trials and a prospective cohort. PLoS One. 2018;13(6):e0199265.
 Wilson E. Abstract 1405: Radiosensitization of breast cancer cells by Vitamin D3 and Vitamin D analogs. In: Tumor Biology. American Association for Cancer Research; 2010.
 Negri M, Gentile A, de Angelis C, Montò T, Patalano R, Colao A, et al. Vitamin D-induced molecular mechanisms to potentiate cancer therapy and to reverse drug-resistance in cancer cells. Nutrients. 2020;12(6):1798.
 Mohr SB, Gorham ED, Kim J, Hofflich H, Garland CF. Meta-analysis of vitamin D sufficiency for improving survival of patients with breast cancer. Anticancer Res. 2014;34(3):1163–6.
 Gaby A. Nutritional Medicine. Concord NH: Fritz Perlberg Publishing; 2011.
 Schwartz JB. Effects of vitamin D supplementation in atorvastatin-treated patients: a new drug interaction with an unexpected consequence. Clin Pharmacol Ther. 2009;85(2):198–203.
 Burt LA, Billington EO, Rose MS, Raymond DA, Hanley DA, Boyd SK. Effect of high-dose vitamin D supplementation on volumetric bone density and bone strength: A randomized clinical trial: A randomized clinical trial. JAMA. 2019;322(8):736–45.
 Reddy P, Edwards LR. Magnesium supplementation in vitamin D deficiency. Am J Ther. 2019;26(1):e124–32.