Is There a Link Between Vitamin D and Breast Cancer?

There has been some disagreement over the connection between vitamin D levels and breast cancer. Current research shows that having low vitamin D levels might be linked to a higher risk for cancer recurrence. Vitamin D offers additional benefits for people trying to lower their risk of breast cancer as well as for people being treated for cancer.

This article gives an overview of vitamin D, the daily requirements, how it might affect your risk for different types of cancer, and its role in your overall wellness. The article will also provide information about breast cancer recurrence and prevention,

A person in side profile with their eyes closed in front of a window; they are partly in shadow and partly have sun on their face.

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What Is Vitamin D?

Vitamin D is also known as calciferol or the “sunshine vitamin." It is a fat-soluble vitamin that helps with teeth and bone development. The human body produces vitamin D naturally through exposure to sunlight. When ultraviolet (UV) rays from the sun are on the skin, it triggers the body to make vitamin D. The vitamin is also present in certain foods and can be taken as a supplement.

Daily Requirements

According to the National Institute of Health (NIH), the daily vitamin D requirements—in both international units (IU) and the equivalent micrograms (mcg)—are:

  • Birth to age one year: 400 IU/day or 10 mcg
  • Between one and age 70 years: 600 IU/day or 15 mcg
  • Over age 70 years: 800 IU/day or 20 mcg
  • Pregnant and nursing people: 600 IU/day or 15 mcg

Foods With Vitamin D

Vitamin D is found in food such as:

  • Fatty fish (trout, salmon, tuna, mackerel, sardines)
  • Fish liver oils
  • Beef liver
  • Egg yolks
  • Shrimp 
  • Mushrooms

Foods can also have vitamin D added to them (fortified). Foods that are commonly fortified with vitamin D are:

  • Milk or milk alternatives
  • Cheese
  • Orange juice
  • Some cereals
  • Yogurt

About 42% of people in the United States are vitamin D deficient. Risk factors for vitamin D deficiency include:

  • Lack of sun exposure 
  • Using sunscreen regularly (which is a good practice) 
  • Having darker skin
  • Not eating enough foods with vitamin D

Some people need to take supplemental vitamin D. These supplements come in two forms: D2 or D3.

D2 is naturally produced by some plants, while D3 is sourced from animals. Research has shown that vitamin D3 supplements increase vitamin D levels better than D2 supplements do.

Vitamin D Supplements

Vitamin D3 is the most common D supplement. It is often combined with calcium. Talk with your healthcare provider before starting any dietary supplement because taking them may change how your other medications work. Your provider may want to test your vitamin D levels and suggest a dosage for you based on the results.

It’s best to find a high-quality supplement brand that is US Pharmacopeia (USP) verified to avoid harmful contaminants, such as mercury. Choosing a high-quality supplement also helps ensure that your body will absorb it well. 

Breast Cancer Recurrence

There is some disagreement among researchers about the connection between vitamin D levels and breast cancer. One reason is that there are many research variables, including different cutoff levels that studies use to measure vitamin D deficiency.  

Many studies have shown that a high percentage of people have low vitamin D levels when they are diagnosed with breast cancer. Current research has found that people with low D levels may have a higher risk for cancer recurrence and cancer spreading (metastasis). 

While there is a need for more randomized clinical trials to understand the connection better, here is what we do know about the possible link between vitamin D and breast cancer: 

  • One study found that 45% of people with breast cancer had vitamin D levels below 20 nanograms per milliliter of blood (ng/ml) at diagnosis (compared to 34% in the control group)
  • The average vitamin D levels in the breast cancer group were 26.88 compared to 31.41 in the control group. 
  • Research has shown that vitamin D has anticarcinogenic properties which means it might help keep cancer cells from growing. 
  • Animal studies have shown that vitamin D may play a role in controlling normal cell growth in breast tissue. 

There are still many unanswered questions about the connections researchers have found between different subtypes of breast cancer, obesity, and more advanced or aggressive cancers.

Further Research Needed

The following are examples of questions researchers still have about vitamin D and cancer:

  • Does breast cancer cause the low vitamin D levels found at diagnosis, or does the low vitamin D cause cancer?
  • How could vitamin D slow tumor progression?
  • What is the relationship between vitamin D levels and prognosis factors such as tumor stage, grade, size, lymph node involvement, and hormone receptor status?
  • Is there a stronger correlation between specific breast cancer subtypes?

Regardless of the connection between vitamin D and cancer, healthcare providers will closely monitor your levels while treating you for breast cancer.

One reason for the need for monitoring is bone health, which is often a concern for people with breast cancer. Treatments such as chemotherapy or aromatase inhibitors decrease vitamin D levels, which lowers calcium absorption and increases the risk of osteoporosis. 

Breast Cancer Prevention

Research has suggested that vitamin D deficiency is a risk factor for breast cancer. However, there is no clear evidence of the therapeutic benefit of using vitamin D supplements to prevent breast cancer. 

What Does the Research Say?

Animal studies have supported the potential for vitamin D supplementation to help with breast cancer prevention. While human clinical trials still need to be done to back this claim, here is what some animal research has shown: 

  • An association between higher vitamin D levels and lower breast cancer risk
  • A protective effect of vitamin D in decreasing cancer risk
  • Tumors spread more quickly, get bigger, are more aggressive, and spread in mice with vitamin D deficiency
  • The potential for prevention from higher vitamin D levels is more prominent for triple-negative breast cancer 

Screening for vitamin D deficiency and the use of supplements has increased over the last 10 years. Healthcare providers and patients have noted the benefits of vitamin D supplements, including:

  • Anti-inflammatory properties
  • Anticarcinogenic (anti-cancer) properties
  • Bone health
  • Increased heart health
  • Stronger muscles
  • Immune function
  • Low cost
  • Few to no side effects or adverse effects

Vitamin D and Other Types of Cancers

There is ongoing research on vitamin D and cancer prevention. One area of interest is whether some types of cancer are more sensitive to vitamin D supplementation than others. Many studies show a relationship between low vitamin D levels and the incidence of other types of cancers, such as:

Overall Wellness

Vitamin D deficiency can have negative effects on your overall health. Your body needs vitamin D to support cardiovascular (heart), reproductive, immune, nervous, and skeletal muscle function.

Some specific roles of vitamin D in the body include:

  • Bone growth and repair by helping the stomach absorb calcium and phosphorus
  • Assisting with muscle movement
  • Letting nerves carry signals to the brain
  • Decreasing inflammation
  • Building immunity
  • Aiding in cell growth and division
  • Helping with glucose metabolism

Vitamin D deficiency can contribute to health problems such as:

  • Depression
  • Sleep disorders
  • Celiac disease
  • Diabetes
  • Osteoporosis and bone fractures
  • Heart conditions
  • Allergies
  • Decreased muscle strength
  • Neuromuscular diseases such as multiple sclerosis
  • Increased infections
  • Rickets (in children)

Effects of Too Much Vitamin D

Vitamin D is generally safe, and low levels are more common than high levels. However, too much vitamin D increases calcium which can cause kidney stones, heart problems, and bone weakness.

While toxicity is rare, it can occur with excessive doses of vitamin D. Signs and symptoms of vitamin D toxicity include:

  • Vomiting
  • Dehydration
  • Pain
  • Loss of appetite
  • Muscle weakness
  • Increased urination
  • Kidney stones
  • Kidney failure


The body naturally produces vitamin D through exposure to sunshine. It's also present in certain foods and can be taken as a supplement.

There is disagreement over the connection between vitamin D levels and breast cancer. However, research has shown that low levels of vitamin D are present at a higher rate in people with breast cancer. Vitamin D also offers additional benefits for people trying to lower their risk of breast cancer as well as for people undergoing cancer treatment. 

A Word From Verywell 

Vitamin D is generally considered safe, is low cost, and has many health benefits, but it’s always best to talk to your healthcare provider before you start taking a supplement. They can monitor your vitamin D levels and make sure you are taking the appropriate dose. 

Frequently Asked Questions

  • Can vitamin D deficiency cause breast cancer?

    Research has linked vitamin D deficiency with breast cancer. However, there are still many unanswered questions, including whether vitamin D deficiency causes breast cancer or if cancer causes vitamin D deficiency. 

  • Does vitamin D help prevent breast cancer?

    While there is promising research, the studies have been inconsistent. Many animal or lab studies have suggested that vitamin D may prevent breast cancer, but human or observational studies have not confirmed this. What is clear is that many people have decreased vitamin D levels when they are diagnosed with breast cancer.

  • Does vitamin D increase estrogen?

    Vitamin D supports the production of healthy reproductive hormones, including estrogen. However, there is no evidence that vitamin D increases estrogen.

16 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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Additional Reading

By Brandi Jones, MSN-ED RN-BC
Brandi is a nurse and the owner of Brandi Jones LLC. She specializes in health and wellness writing including blogs, articles, and education.