Unclear, Disproven, and Controversial Breast Cancer Risk Factors

Research on some potential breast cancer risk factors is still ongoing, and a few commonly believed links have been disproven altogether. Learn more about what the science currently shows.

Factors with unclear effects on breast cancer risk

There are some things that might be risk factors for breast cancer, but the research is not yet clear about whether they really affect breast cancer risk.

Diet and vitamins

The possible link between special diets and breast cancer risk is not clear. Results of some studies have suggested that diet may play a role. Others have not found that diet influences breast cancer risk.

Mediterranean diet: Diets high in plant-based foods, fish, and fats, such as olive oil, have benefits for health. Yet, their impact on breast cancer risk is not clear. Some studies have found a Mediterranean style diet may lower breast cancer risk, but more studies are needed to confirm this.

Fat intake: Studies on whether high-fat diets increase the risk of breast cancer do not have consistent results. Some studies suggest a lower risk of dying of breast cancer with low fat diets, but more studies are needed to understand this.

We do know that high-fat diets can lead to having excess body weight (overweight or obesity). This is a known breast cancer risk factor. A diet high in fat is also a risk factor for some other types of cancer. And eating certain types of fat is clearly linked to a higher risk of heart disease.

Fruits and vegetables: Having a diet high in fruits and vegetables may decrease your risk of getting certain types of breast cancer, but it is not clear if fruits and vegetables in the diet can lower the risk of breast cancer overall. Studies have shown that deaths related to breast cancer are lower in women who eat a low-fat diet, which often includes larger amounts of fruits, vegetables, and grains.

Soy: It is not clear if eating soy-based products can reduce the risk of breast cancer in Western countries. Some studies in Asian countries suggest that soy can lower the risk of developing breast cancer.

Red or processed meats: Some studies show that red meats and processed meats may increase the risk of breast cancer. Others show no impact of red meat or processed meat intake on breast cancer risk.

Fiber intake: Newer studies suggest that fiber intake might play a role in the risk of breast cancer. Eating more dietary fiber could slightly reduce the risk of breast cancer.

Vitamin D: Studies of vitamin D have not shown a clear link between vitamin D supplements, blood levels, and risk of breast cancer.

The lack of a strong link between diet and breast cancer in studies so far doesn’t mean that it’s not important to eat a healthy diet. A diet low in fat, red meat and processed meat, and high in fruits and vegetables can have many health benefits. This type of diet may also lower your risk of some other types of cancer.

Chemicals in the environment

A great deal of research has been done to understand possible environmental influences on breast cancer risk. Researchers are especially looking at certain chemicals that may have hormone effects. These are called phthalates. These chemicals can be used in plastics and included in some personal care products. Because these chemicals may mimic estrogen, they could affect breast cancer risk. However, no studies have shown a clear link.

Studies of exposure to some organochlorines, such as polychlorinated biphenyls and certain pesticides, have not shown any increased risk of breast cancer.

It can be difficult to do studies on chemical exposures and cancer risk. However, research is ongoing.

Night shift work

Night shift work puts unique stress on the body and its normal sleep-wake cycle. Researchers are trying to understand the link between night shift work and cancer. The effect may be due to changes in levels of melatonin, a hormone that’s affected by the body’s exposure to light. But other hormones are also being studied.

Disproven or controversial breast cancer risk factors

You may see information online or hear about controversial risk factors that have been disproven. These risk factors do not cause cancer. It's important to learn the facts. Here are some factors that research has shown are not linked to breast cancer.

Breast implants

Breast implants have not been shown to increase the risk of breast cancer. People with breast implants have not been shown to have more cancer recurrence compared to those without implants.

Breast implants have been associated with other types of cancer. This includes a rare form of lymphoma called anaplastic large cell lymphoma (ALCL).

See Breast Reconstruction Using Implants for more information.

Antiperspirants

Online and social media rumors have suggested that chemicals in underarm antiperspirants are absorbed through the skin. They may say the antiperspirants interfere with lymph circulation and cause toxins to build up in the breast, causing cancer.

Based on the available evidence, there is little if any reason to believe that antiperspirants increase the risk of breast cancer. For more information, see Antiperspirants and Breast Cancer Risk.

Bras

There is no scientific or clinical data that shows that wearing a bra changes the risk of having breast cancer. This data includes a 2014 study of more than 1,500 women.

Abortion or miscarriage

The most up-to-date scientific research suggests that abortion does not influence a woman’s risk of breast cancer.

Several studies have provided very strong data showing that neither induced abortions nor miscarriages (spontaneous abortions) have an overall effect on the risk of breast cancer. For more detailed information, see Abortion and Breast Cancer Risk.

More resources

Learn more about risk factors for breast cancer.