The bad news: Many women diagnosed with breast cancer have been found to be deficient in vitamin D. Could their diagnosis have been prevented? The good news: optimizing blood levels of Vitamin D may significantly reduce the risk of more than a dozen types of cancer, including breast, pancreatic, colorectal, ovarian, and prostate. When it comes to breast cancer prevention, vitamin D may be the most important vitamin of them all.

According to the National Center for Biotechnology Information, “Calcitriol (1,25-dihydroxyvitamin D3), the hormonally active metabolite of vitamin D, inhibits the growth of many malignant cells including breast cancer cells” by inhibiting estrogen synthesis. ”Calcitriol and its anti-inflammatory actions will play an important role in the prevention and/or treatment of breast cancer.” [i]

Vitamin D US RDA is Too Low

Many vitamin D health experts recognize that the US RDA of vitamin D is inadequate for optimal health. And because each of us assimilates vitamin D uniquely, it is better to monitor the result of dosage rather than the dosage itself. That way you can adjust the dosage to achieve the desired effect.

The most accurate way to measure how much vitamin D is in your body is the 25-hydroxy vitamin D blood test. A level of 50 nanograms/milliliter to 70 ng/mL is considered optimal for healthy people. (70 – 100 ng/mL is recommended when treating cancer and heart disease.) This is in stark contrast to the medical standard suggesting that 20 ng/mL is adequate.

The optimal range offers greater protection from issues including not only osteomalacia (softening of the bones), osteopenia (reduced bone mass), and osteoporosis (brittle, fragile bones), but also thyroid conditions, kidney disease, heart disease, autoimmune disorders, cancers and more.[ii]

There is no risk of toxicity until achieving levels above 200 ng/ml. So 200 ng/ml is the higher threshold for toxicity, and 40 ng/ml is the lower threshold for therapeutic benefit. Ask your health provider or order your 25-hydroxy vitamin D blood test on-line (perhaps through the Vitamin D Council.)

Forms of Vitamin D

While vitamin D2 is available through plant-based sources, it is D3 that we really need. D3 is far more beneficial to our health than D2 and only available through animal-based sources like fatty fish, animal livers, egg yolk and raw (unpasteurized) milk. (Cod liver oil is a potent source of D3.) When exposed to sunshine, our skin also synthesizes vitamin D3, which is water soluble, while oral vitamin D3 supplements are fat soluble.

In Colorado we live well above the equator, where there is insufficient ultraviolet-B radiation for vitamin D synthesis from November to early March. Because sunlight won’t be sufficient at certain times of the year or in certain places, and because the body’s ability to manufacture vitamin D declines with age, nutritional supplementation is essential for sustaining optimal blood levels.

Medical Conditions that Increase the Need for Vitamin D

Vitamin D must pass through the liver and the kidneys in order to become available for active use by the body. Hence, diseases of those organs can affect the formation of active vitamin D, including:

Intestinal diseases such as Crohn’s, celiac, cystic fibrosis
Kidney disease leading to failure
Liver disease
Overactivity of the parathyroid glands
Pancreatic disease
Surgical removal of the stomach
Surgical removal of the end of the small bowel (terminal ileum)

Supplementing with active forms may be necessary. However, these forms are not mere supplements, so doctors prescribe them as part of a treatment regimen.

Medications that Interfere with the Absorption of Vitamin D

Antacids and acid blcokers: Tagamet, Pepcid, Axid, Zantac
Highly Active Antiretroviral Therapy, (for AIDS)
Mineral oil or products containing mineral oil
St. John’s Wort

How to Take Oral D3

When you increase your intake of vitamin D3, be sure to increase your intake of vitamin K2. And because vitamin D3 is a fat-soluble vitamin, it is best taken with healthy fats like organic: avocado, coconut and nut; and organic, pasture/grass-fed: butter, clarified butter (ghee), egg yolk, and meat. Vitamin D3 also needs sufficient amounts of magnesium, zinc and other trace minerals to work properly, so be sure to stay adequately mineralized each day. For more information on vitamin K2, healthy fats and minerals, please see their separate sections in Our Daily Bread or articles under the Preventive Support page.

While a dosage of only 5,000 IUs of vitamin D3 a day may enable you to reach and maintain a blood level of at least 40 ng/ml, I typically consume 5,000 – 20,000 IUs of Vitamin D3 daily via Thorne Vitamin D/K2 sublingual drops, available at and many health food stores. (I used to use: Carlson D3 drops and Biotics Emulsified D3 drops, but found them less absorbable for me and they do not include Vitamin K2.) It’s important to find the formula and dosage best for your body. I typically consume vitamins D and K with a meal that includes butter, Green Pastures Fermented Cod Liver Oil, or New Chapter WholeOmega since these are fat-soluble vitamins.

[i] Krishnan AV, Swami S, Feldman D. Vitamin D and breast cancer: inhibition of estrogen synthesis and signaling. J Steroid Biochem Mol Biol. 2010 Jul;121(1-2):343-8. doi: 10.1016/j.jsbmb.2010.02.009. Epub 2010 Feb 13. (Pubmed 20156557)

[ii] Mayo Clinic

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by Tirza Derflinger
Founder, Author, Lead Educator, Speaker, CTT, MBA
Better Breast Health – For Life!™
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