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Breast Cancer and Nutrition: The Effects of Alcohol, Soy, and Sugar

You may be familiar with the phrase; you are what you eat. What may surprise you is that its origins date back to the 1800s, when a French lawyer, politician, and famous gastronome, was said to have first uttered a similar French version of the popular saying. Since then, the concept has been the basis for best-selling books and entire nutrition plans.

We’ve known for a long time that diet contributes to our health. It’s a simple concept: good nutrition helps children grow and develop and contributes to health over a lifespan. An unhealthy diet is associated with harmful effects, including obesity, heart disease, and stroke, Type 2 diabetes, and cancer. Studies have also found a correlation between a diet high in refined sugars and impaired brain function—and evidence that it can worsen symptoms of mood disorders, such as depression.

The Connection Between Breast Cancer and Nutrition

It’s probably likely that you’ve heard conflicting reports about the effect of certain foods on breast cancer. One year you read that soy contributes to breast cancer, and a year later, you read that soy reduces breast cancer. Understandably, a person could easily become confused and frustrated. What is going on? Why can’t they get it right?

Science is constantly evolving. Advances in technology enable researchers to gain new information and learn new things. A great example of this is the progress of genetic testing for breast cancer that became available only twenty-five years ago. That new knowledge may lead scientists to draw new conclusions that contradict earlier information. It doesn’t mean that the science is flawed, only that new evidence has been discovered.

Alcohol and Breast Cancer

Multiple studies have shown a link between alcohol consumption and breast cancer. Two landmark papers published in The New England Journal of Medicine in 1987 determined that, even at moderate levels, alcohol consumption was associated with risk of breast cancer. Since then, numerous global studies have been conducted with the same findings.

Several studies examined alcohol consumption with other known breast cancer risk factors, such as diet, genetic conditions, body mass index, physical activity levels, and smoking.

Soy and Breast Cancer

There’s been a lot of debate over the past 25 years on whether soy increases breast cancer risk. On the contrary, recent research findings indicate that soy and soy-based foods, including tempeh, tofu, and miso, lower breast cancer risk.

A study commissioned by the National Cancer Institute and the World Cancer Research Fund determined that the culprit is cow’s milk. Drinking cow’s milk increases a woman’s risk of breast cancer by as much as 80 percent compared with drinking soy milk.

The Mayo Clinic chalks-up the confusion to isoflavones (plant estrogens) found in soy. High levels of estrogen have been linked to an increased risk of breast cancer; however, the levels of isoflavones in food sources of soy aren’t high enough to increase breast cancer risk.

Soy or isoflavone supplements, however, generally contain higher isoflavone levels. Some studies have suggested a link between soy or isoflavone supplements and an increased risk of breast cancer in women who have a family or personal history of breast cancer or thyroid problems. It’s helpful to understand the differences between natural, unprocessed soy and soy supplements and additives.

Sugar and Breast Cancer

Sugar has been implicated as a cause of breast cancer, depicted as providing a feeding frenzy enabling cancer cells to grow out of control quickly. Like all cells, cancer cells require energy to grow and multiply and use glucose as their primary fuel source.

Glucose is the simplest form of sugar and comes from any food that contains carbohydrates. That list includes healthy foods, such as vegetables, fruits, dairy, whole grains, refined carbohydrates, and food with added sugars, such as white bread, pasta, sweetened beverages, and sweets.

The idea that sugar expedites cancer cells’ growth has led some people to completely cut out all carbohydrates from their diet based on the belief that cancer cells need glucose; eliminating it will stop cancer growth. Sugar has not been found to make cancer cells grow faster, nor has cutting sugar out of your diet been connected with slowing down cancer cells’ growth. It’s not that simple.

Glucose is a critical component needed for healthy cells to function, and there is no way for our bodies to let healthy cells have the glucose they need but stop it from feeding the cancer cells. Removing carbohydrate intake from the foods we eat doesn’t work because our bodies will make glucose from other sources, such as protein and fat.

There is an indirect link between sugar and cancer. We know that eating a lot of sugary foods such as cakes, cookies, and sweetened beverages can contribute to weight gain and excess body fat. Research has shown that being overweight or obese increases the risk of 11 types of cancers, including postmenopausal breast cancer.

Another study in the American Journal of Clinical Nutrition found that in a cohort of more than 100,000 people whose dietary intake was assessed every six months, sugar was associated with cancer, especially with breast cancer. Sugars from fruit, however, were not associated with cancer risk. Some scientists are investigating the possibility of measuring sugar to detect breast cancer.

We continue to learn the impact of nutrition on our health and how understanding our dietary choices can benefit our ability to prevent breast cancer. Following a healthy diet can also help you feel your best. Explore our guidelines for a healthy diet, and become part of our empowering community, including our Breast Cancer Survivor & Friends Meet and Greets. We’re always here for you!


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