Breast Cancer Risk is Reduced with Vitamin D and Weight Loss

Breast cancer risk is reduced with Vitamin D and weight loss in obese, post-menopausal women diagnosed with the disease.

What is Breast Cancer?

Cancer is a disease in which abnormal cells divide uncontrollably and destroy body tissues. In the case of breast cancer, these abnormal cells are formed in the breast. Initially, it is a lump which can sometimes be felt. A medical imaging procedure may help doctors capture and diagnose this tumor with radiography, mammogram, or sonogram.

Tumors of the breast can be malignant or benign. The cancer is considered malignant when its cells divide without control and have the ability to invade nearby tissue. They can also spread to the blood and lymph systems making a person very sick. A benign tumor is very common in the breast and is non-malignant. They will not spread. However, studies have shown that they are linked to a higher risk of getting breast cancer later on.

Breast cancer is the most commonly diagnosed cancer in women. One in 8 women in the United States will develop invasive breast cancer in her lifetime. Another one in 32 women be diagnosed with in-situ breast carcinoma (abnormal breast cells that haven’t yet turned malignant). Breast cancer is the second leading cause of cancer death in women. Therefore, it is important to determine the cause so that it may be prevented, and some studies have indicated that breast cancer is reduced with Vitamin D and weight loss.

What are the Risk Factors for Breast Cancer?

According to the American Cancer Society®, hormones are thought to influence breast cancer risk by increasing cell proliferation which likely causes DNA damage and then promotes cancer invasion. Breast cancer risk is also higher in women over the age of 40 who are experiencing perimenopause, menopause, and post-menopause. One-third of post-menopausal breast cancers are thought to be caused by modifiable lifestyle behaviors. Following are some other risk factors of breast cancer:

  • Family history (especially in a first degree relative)
  • Genetic predisposition (inherited mutations such as in BRCA1 and BRCA2)
  • Previous history of breast cancer
  • Ductal carcinoma in situ (DCIS)
  • Lobular carcinoma in situ (LCIS)
  • Benign breast disease
  • Dense breast tissue
  • Taller women
  • Early menstruation (before age 11)
  • Late menopause (after age 55)
  • High bone mineral density in post-menopausal women
  • High levels of estrogen and androgen in post-menopausal women
  • First pregnancy after age 35
  • Fertility drugs (more than 12 clomiphene treatment cycles)
  • Lack of breastfeeding
  • Hormonal birth control
  • Hormone replacement therapy
  • Obesity
  • Physical inactivity
  • Poor diet (overconsumption of soy; lack of vegetables and fruit)
  • Nutrient deficiencies (B, C, D3, K2, iodine, magnesium, selenium, iron)
  • Alcohol consumption
  • Tobacco use
  • Radiation exposure
  • Diethylstilbestrol exposure (DES)
  • Environmental pollutants
  • Circadian rhythm disruption (night shift work)

Why Vitamin D Reduces Breast Cancer Risk?

While Vitamin D is known for its health benefits of keeping bones strong, new studies show that almost nearly all obese post-menopausal patients with breast cancer are Vitamin D deficient. Similar studies have also shown a link between Vitamin D and breast cancer mortality. Breast cancer patients with the highest Vitamin D concentrations had a 50 percent lower death rate than those with lower concentrations. These studies suggest that Vitamin D deficiency is a risk factor for breast cancer in women with higher body fat. Vitamin D may reduce cancer risk by inhibiting cell proliferation.

How do I Get Adequate Vitamin D?

You can increase your intake of Vitamin D from direct sunlight exposure, foods rich in its source, and supplementation. Following are the recommended dietary allowances (RDAs) for Vitamin D. Please note that this is the minimum dosage needed by the body on a daily basis according to the United States National Institutes of Health. For certain health conditions or optimal health, more may be needed depending on the health condition.

  • 0-12 months of age: 400 IUs
  • 1-50 years of age: 600 IUs
  • 70+ years of age: 800 IUs

Vitamin D through Sunlight

The most natural way of getting Vitamin D is by exposing bare skin to sunlight. The more skin you expose, the more Vitamin D is produced in your body. Lighter skin exposed to sunlight will accumulate the benefits of Vitamin D much quicker than someone with darker skin. Someone with light skin can produce 10,000 to 25,000 international units (IUs) of Vitamin D in just 15 minutes. Very dark skin people may need to longer sunlight exposure. Sun exposure between the hours of 10 AM and 3 PM for five to 30 minutes per day on the face, arms, legs, or back without sunscreen usually leads to sufficient Vitamin D synthesis.

Vitamin D through Food

Very few foods naturally contain Vitamin D. The best sources include cold-water fish such as salmon, tuna, and mackerel. Fish liver oils are also a good source. Small amounts of Vitamin D are found in beef liver, egg yolks, and cheese. Some mushrooms also provide Vitamin D. You may find fortified Vitamin D in some prepackaged foods like milk, orange juice, and cereal. However, these are not good sources of food to include in a healthy diet as they are filled with sugars and additives.

Vitamin D through Supplementation

Vitamin D supplementation is available in two forms: D2 (ergocalciferol) and D3 (cholecalciferal). Research has shown that they are equivalent based on synthesis and their ability to cure rickets, a bone disease caused by Vitamin D deficiency in children. However, Vitamin D2 is less potent at high doses than Vitamin D3. Most likely, you will find Vitamin D3 in quality pharmaceutical supplements. Vitamin D2 is more difficult to find.

Where Can I Get a Quality Vitamin D Supplement?

Following are a few high quality Vitamin D supplements. You may click on the link to read about each and also purchase. They are available for infants to adults in liquid, gummy, gel capsules, and vegetarian capsules.

For Infants

Nordic Naturals® Baby’s Vitamin D3

For Children

Nordic Naturals® Vitamin D3 Gummies for Kids

For Adults

Pure Encapsulations® Vitamin D3, 400 IU

Nordic Naturals® Vitamin D3 Gummies, 1,000 IU

Nordic Naturals® Vitamin D3 1000 soft gels

Pure Encapsulations® Vitamin D3, 1,000 IU, vcaps

Pure Encapsulations® Vitamin D3 Liquid, 1,000 IU

Pure Encapsulations® Vitamin D3 (Vegan) Liquid, 1,000 IU

Nordic Naturals® Vitamin D3 5000 soft gels

Pure Encapsulations® Vitamin D3, 5,000 IU, vcaps

Pure Encapsulations® Vitamin D3, 10,000 IU, vcaps


To prevent breast cancer, implementing good lifestyle habits is important. Be sure to maintain a healthy weight, get plenty of sunshine, and eat a whole foods diet that includes cold-water fish like salmon or tuna. When you can’t get enough sunshine such as on rainy or winter days, be sure to supplement your diet with a high quality Vitamin D supplement.


Dr. Abby Campbell
EditorDr. Abby Campbell
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