Myths and Facts about Cancer and Vitamin D

Medically Reviewed by Melinda Ratini, MS, DO on September 21, 2023
3 min read

A few decades ago, scientists noticed a pattern: people in sunnier parts of the world had lower rates of cancer and fewer deaths from the disease than places that got less sun.

To explain the difference, researchers started studying the effects of vitamin D, a nutrient that the body makes when sunlight hits the skin.

After years of research, there are still no definite answers about whether it can prevent cancer or play a role in its treatment. But scientists have learned some things about the connection so far, and they’re still investigating it. Here are some common myths and facts about vitamin D and cancer.

young family walking in the sun

There isn’t enough evidence to recommend vitamin D for every form of the disease. In fact, one large study found that taking vitamin D3 and calcium did not lower the overall chances of getting cancer in healthy women after menopause.

Plus, when scientists reviewed the results of several studies, they found that vitamin D does not seem to lower the odds for several kinds of cancer, including:


Scientists have done a lot of research on the role of vitamin D in colorectal cancer. The results haven’t been totally consistent, but a number of studies found that higher levels of vitamin D are linked with a lower chance of getting the disease.

Clinical trials are still looking into the connection, including how the vitamin affects people who take it along with their treatment for colorectal cancer.

Vitamin D may lower some women’s odds of getting the disease, but research shows it doesn’t prevent breast cancer overall. Women who are low on vitamin D to begin with may get more benefits from taking it than others.

Other findings have linked low levels of vitamin D with higher chances of breast cancer.

  • Among women in the early stages of the disease, those low on vitamin D were more likely to have cancer come back later than women with normal levels. The low-vitamin D women also had a greater chance of dying from the disease.
  • Women with healthy levels of vitamin D had 63% lower odds of breast cancer than women who didn’t have enough of it.
  • In mice, too little vitamin D seemed to help breast cancer cells grow.


Around the world, almost 50% of people don’t get enough vitamin D. Since it’s so important to many parts of your health, you may get some benefits from taking a vitamin D supplement.

Before you head for the vitamin aisle, ask your doctor if it’s safe for you to take vitamin D. If you take medications, it could affect how well they work. Your doctor may also want to test your blood to see how much vitamin D you have. That can help them know the right dose for your body.

Finally, if a fear of cancer is the main reason you want to take vitamin D, tell your doctor about that, too. It’s true there may be some promising findings about vitamin D in some types of cancer, such as colorectal and breast cancers. But you should also find out about other, proven ways to lower your odds of getting cancer. One of the best ways is to make sure you get the cancer screenings you need when your doctor recommends them. That will raise your chances of catching any problems early on.