Causes of Breast Cancer: Bras? Antiperspirants? Stress?

Patient Expert

One of the first things a person does when diagnosed with breast cancer is to wonder what caused it. Women start thinking about everything that might have affected their breasts. Could it have been that tight bra? Could that letter circulating on the internet about antiperspirants causing breast cancer be right? Did that recent divorce or death in the family cause their breast cancer?

Many researchers are wondering what causes breast cancer too, and so far no one knows for sure. We do know some risk factors for breast cancer, but risk factors and causes are different.

A risk factor is a condition that is more common in people with the disease. One risk factor for breast cancer, for example, is age. We know that older women are much more likely than younger women to get breast cancer and that the majority of breast cancer patients are over sixty. Does age cause breast cancer? Of course not. The majority of elderly women do not get breast cancer.

When scientists are researching the cause of a disease, they start looking for correlations among the people who have that disease. A well-known example is tobacco smoking and lung cancer. Scientists started noticing that lung cancer rates had risen as the number of people smoking had risen and that most people with lung cancer were smokers. This high correlation between tobacco use and lung cancer led scientists to hypothesize that smoking might be one cause of lung cancer.

The tobacco industry fought back saying this conclusion was shoddy science. Maybe some third factor was causing the rise in lung cancer, not smoking. Correlation and causation are not the same. But the scientists tested out their hypothesis and were able to show that tobacco is in fact a carcinogen.

In this article, I'll look at three factors that have a high correlation with breast cancer but which do not cause it: bras, antiperspirants, and stress. In later articles, I'll discuss some risk factors that may give clues to the causes of breast cancer.

Bras. One theory is that bras cause breast cancer, especially tight bras or underwire bras. Almost every women in the United States who gets breast cancer wears a bra. There is an extremely high correlation between bra wearing and breast cancer. Unfortunately this theory ignores the fact that almost every woman in the United States who does not get breast cancer also wears a bra.

Breast cancer happened to women well before the invention of the bra in the 1920's. It happens to women in cultures where bras are not worn. Dr. Susan Love, breast cancer expert, says, "Wearing a bra is neither physically harmful nor medically necessary." She dismisses the theory that wearing an underwire bra could cause cancer as "total nonsense."

Antiperspirants and deodorants. Another habit with a high correlation to breast cancer is using antiperspirants or deodorants. Again in the United States, most women use these products, so it is not surprising that most women who get breast cancer have used them. The theory goes that antiperspirants block the elimination of sweat and somehow cause toxins to build up that cause cancer.

A National Cancer Institute (NCI) fact sheet explains another possible mechanism, "Aluminum-based compounds are used as the active ingredient in antiperspirants. These compounds form a temporary plug within the sweat duct that stops the flow of sweat to the skin's surface. Some research suggests that aluminum-based compounds, which are applied frequently and left on the skin near the breast, may be absorbed by the skin and cause estrogen-like (hormonal) effects."

However, the fact sheet goes on to detail the studies on this topic and concludes that no credible evidence links antiperspirant use and breast cancer. One European study of breast cancer patients found that early underarm shaving and antiperspirant use seemed to be related to diagnosis of breast cancer at an earlier age. However, because this study did not have a control group of non-breast cancer patients, it is hard to draw conclusions, especially when other studies find no connection.

If you have other risk factors for breast cancer and want to be super-cautious, just in case, you could switch to a natural deodorant without aluminum in it. However, there are plenty of other things more deserving of your worry.

Stress. There seems to be so much to worry about today. Almost every person diagnosed with breast cancer can pinpoint a recent stress. It becomes easy to blame that stress on causing the cancer. From there, it may be easy to blame the person most responsible for the stress--a straying husband, a difficult child, or an unreasonable boss.

However, breast cancer starts years before the first symptoms appear. One cell mutates and starts growing abnormally until it becomes a tumor large enough to detect. Stress did not cause the change in that original cancerous cell.

Yet so many people with cancer talk about stress in the weeks and months before their diagnosis, surely there must be some connection. Maybe there is.

Again there is a high correlation between stress and cancer partly because there is a high correlation between stress and life. But there may be more to it. Studies into the connection between stress and disease have learned that stress increases our bodies' production of hormones like adrenaline. Too much of these substances can lead to disease. But there is no connection between stress and breast cancer specifically.

I had a friend in an extremely stressful work situation in which most of the people eventually lost their jobs. Within two years, my friend had thyroid cancer. He firmly believed that the work-place stress led to his disease. He pointed out that most of his coworkers suffered cancer, heart disease, or other major health issues. The stress reduced their bodies' ability to heal, which is different from saying that stress causes a particular disease.

The NCI fact sheet on this topic explains, "Studies have indicated that stress can affect tumor growth and spread, but the precise biological mechanisms underlying these effects are not well understood." The fact sheet further explains that studying the effects of stress on disease is very difficult. Setting up controlled experiments that result in disease is not possible, and stress often leads to behaviors like drinking or smoking that may themselves cause illness. So there are no conclusive studies that prove stress causes cancer.

While stress does not cause breast cancer, it may reduce the body's ability to fight it. People in stressful situations may want to seek counseling, exercise, or learn other stress reduction techniques to help their bodies overcome the harmful effects of chronic stress.

Understanding the causes of breast cancer is important. Once that is known, we will be closer to a cure. Understanding risk factors can help individuals manage their health. Knowing that you don't need to worry about your bra or antiperspirant may reduce your overall stress and increase your health.