Vitamin D: What Is Its Role in Preventing Breast Cancer?

Why you need it and who's likely deficient
Vitamin D: What Is Its Role in Preventing Breast Cancer?

Are you getting enough vitamin D, aka the “sunshine” vitamin? Among other risks, not having enough of this protective vitamin could put you at higher risk for developing breast cancer. Additionally, research links higher levels of the micronutrient with better outcomes if you have breast cancer.

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Holly Pederson, MD, Director of Cleveland Clinic’s Medical Breast Services, explains why vitamin D is so important and shares her best advice on how much is enough and how to make sure you’re getting it.

What does research say about vitamin D?

“Vitamin D is an important co-factor in a lot of processes in your body,” Dr. Pederson says. “But most people aren’t getting enough.”

Research links low vitamin D levels to a range of health problems, including:

  • Sleep disruption.
  • Diabetes.
  • High blood pressure.
  • Muscle weakness.
  • Accidents and falls.
  • Multiple sclerosis.

Research also suggests that having low vitamin D levels may increase your chances of getting certain types of cancer, including breast cancer. According to the study, those with the highest levels of vitamin D in their blood had a 45 percent decrease in breast cancer risk compared with women with the lowest levels of vitamin D in their blood.

Another study strongly associates higher vitamin D levels at diagnosis with better survival rates among women with breast cancer.

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But it’s important to note that variants in your vitamin D receptor gene (that governs how your cells absorb the vitamin) may influence vitamin D’s ability to prevent cancer or make cancer less severe if it occurs, regardless of the level in your blood, Dr. Pederson says.

Where does vitamin D come from?

Vitamin D differs from other micronutrients. Your body actually produces the vitamin when you expose your skin to ultraviolet B radiation from the sun, Dr. Pederson says.

You can also get some of the vitamin in your diet. Salmon, fresh tuna and mackerel are natural sources. Milk, yogurt and some breakfast cereals are fortified with vitamin D, or you can take a vitamin supplement.

How do you know whether you’re getting enough?

There aren’t any hard and fast symptoms that crop up if your body isn’t getting enough vitamin D, Dr. Pederson says. But you’re more likely to have a deficiency if you live in a colder climate that receives less sunlight during winter months.

You’re also more likely deficient if you have a high body mass index (BMI), or if you have darker skin (more melanin in your skin blocks the sun’s ultraviolet B rays), she says.

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With so many variables at play, how can you know for sure about your vitamin D levels?

Dr. Pederson recommends the following:

  1. Start taking a daily supplement of 1,000-2,000 units of vitamin D.
  2. Wait six months.
  3. Ask your doctor to draw your blood to check your levels.
  4. Maintain a vitamin D level in the normal range.

While taking a vitamin D supplement is safe for most everyone, you should check with your doctor first if you have a history of kidney stones, she says.

Although many studies have addressed the relationship between vitamin D and breast cancer risk, there isn’t agreement on just how much of the vitamin you need to reduce your risk. But Dr. Pederson recommends maintaining a normal vitamin D level because it is also shown to support bone density.

“Until policies and recommendations are made based on data, it’s reasonable to maintain your vitamin D level in a normal range, which may reduce your risk of getting breast cancer, and improve survival if you do get it,” she says.

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