Does Vitamin D Decrease Breast Cancer Risk?

by | Sep 30, 2015 | Health & News

October is breast cancer awareness month! This month’s blogs will focus on how we can reduce our risk of developing breast cancer. As many of you know, I am a huge proponent of adequate Vitamin D intake. There are still some skeptics out there, but I hope to change their mindset after reading this week’s blog regarding how Vitamin D levels relate to breast cancer risk and survival.

The function of Vitamin D: what does it do?

Let’s first start with what Vitamin D does for us. Vitamin D helps our bodies absorb calcium, which is essential for good bone health. Vitamin D also helps the immune, muscle and nervous systems to function at their optimal level. Most vitamin D is made when an inactivated form of the nutrient is activated in your skin when exposed to sunlight. Smaller amounts of Vitamin D can be found in fortified milk, fatty fish and eggs.

vitamin d sources, to help reduce breast cancer risk


In the last decade, the use of Vitamin D supplements has soared. In the United States during the period of 2002 – 2011, sales of Vitamin D supplements increased more than 10-fold, from $ 42 million to $ 605 million. (1)

Why do we need supplements? Don’t we get enough from the sun?

As we age, our skin does not absorb as much Vitamin D from the sun as when we were younger. In addition, we have been cautioned by our dermatologists regarding the harmful effect of ultraviolet radiation on skin cancer risk. Thus, many of us are applying more sunscreen to prevent skin cancer—- this also decreases the amount of Vitamin D that our bodies can absorb.

Some studies recommend short periods of sun exposure —15 minutes 3-4 times a week for example,— to provide the recommended daily amount of Vitamin D. I have found that even in sunny San Diego, the levels of Vitamin D in my patients can be extremely low.



Amount recommended for Cancer prevention: How much should we take?

Before you adjust your Vitamin D intake, it is important to have your Vitamin D level checked. This can be done with a simple blood test that can be ordered by your primary care provider. Vitamin D researchers recommend a serum level of between 40-60 ng/ml (nanograms/milliliter). Fellow colleagues and I recommend a slightly higher range, preferring a level of 50-70 ng/ml for breast cancer prevention (as well as prevention of other cancers).

Research has shown a definite correlation between Vitamin D levels and breast cancer risk as well as survival after a breast cancer diagnosis. Women with low levels of Vitamin D have a higher risk of breast cancer. (2) In addition, high Vitamin D levels have shown higher survival rates among breast cancer patients. A recent meta-analysis looked at 5 studies and found that women diagnosed with breast cancer who had high levels of Vitamin D were twice as likely to survive compared to those with low levels of Vitamin D.



How does Vitamin D help with reduction of breast cancer risk?

According to Cedric Garland, Ph.D., from the Department of Family and Preventive Medicine at the University of California, San Diego, “Vitamin D makes cell stick together, particularly breast epithelial cells”. This occurs through the production of a certain molecule called E-cadherin. Dr. Garland continues that “ if Vitamin D level gets low, the cells of the breast epithelium don’t adhere to each other, and when a cell is not tightly adhered to its neighbors, its stem cell undergoes mitosis”. Mitosis is cell division. The cells that reproduce the fastest then can produce a cancerous clone of rapidly dividing cells. These cells can ultimately penetrate the cell membrane, leading to leakage into the lymphatics (also known as metastases). When Vitamin D levels are high, the cells stick together and decrease the risk of cell division thus reducing the risk of metastases.

Pretty amazing, right? And Dr. Garland is right in our backyard – at UCSD!

What should you do?

doctor with female patient

Ask your health care provider to check your Vitamin D level (25-OH Vitamin D) as well as your calcium level (3). If you are deficient in Vitamin D, supplementation might be recommended if your calcium level is normal. If your calcium level is not normal, then other testing should be done to evaluate the Vitamin D deficiency.

There are many ways to increase your Vitamin levels from sub-drops (1,000 – 5,000 iu) to high dose capsules ( 50, 000 iu).   Please consult with your health care provider before adjusting your intake.

In health and happiness!

Dr Diana Hoppe OBGYN in encinitas, CA. signature- hormones, menopause, weight loss, pap smear, total women's health care


  1. Lancet, 2014; 383: 146-155
  2.   Anticancer Research, March 2014