Carbs Raise Risk for Breast Cancer—But Which Ones?

March 5, 2012
Daily Health News
Edmond doctoral student, Cancer Prevention Control Program, University of California-San Diego Moores Cancer Center, San Diego, and Graduate School of Public Health, San Diego State University.

A new study shows that when it comes to preventing breast cancer recurrence, not all carbs are created equal—certain kinds may raise your risk more than others.

To find out more, I talked to study author Jennifer A. Emond, MS, a public health doctoral student at University of California-San Diego. Emond and her colleagues presented their findings at a recent symposium.


Investigators looked at data from 2,651 breast cancer survivors (average age 53). All had been diagnosed with breast cancer within the previous four years. In phone interviews at the beginning of the study and again one year later, the women reported what they had eaten in the past 24 hours. The women were then monitored for about seven years, on average, to see whose breast cancer recurred.

Researchers examined the relationship between breast cancer recurrence and carbohydrate intake—first looking at quantity (did their overall carb intake increase or decrease?) and then at quality (what were the carbs made of?).

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Quality is important to analyze, because the fact is, carbs can be made up of varying amounts of many different constituents, including starch, fiber, sucrose and fructose, and each constituent affects metabolism differently. For example, a typical slice of white bread contains 10.4 grams of starch and less than one gram of fiber. In contrast, a cup of raw carrots contains 3.6 grams of fiber and only 1.8 grams of starch.

Emond and her team discovered…

  • Women who experienced a breast cancer recurrence in the seven-year follow-up period had increased their overall carb intake during that first year by about 2.3 grams a day, on average, while those who did not have a recurrence during that seven-year period decreased their overall carb intake during that first year by approximately 2.7 grams a day, on average.
  • Changes in the amount of starch eaten accounted for the majority of the changes in total carb consumption (compared with other types of carbs, such as glucose, sucrose, galactose, fructose, lactose and maltose.

“The results show that it’s not just overall carbohydrate intake but particularly starch intake that ups the risk for breast cancer,” said Emond.


Scientists do not understand exactly how starches increase the risk for breast cancer recurrence, but multiple studies indicate that elevated insulin is associated with higher breast cancer risk—and many starches are known to elevate insulin faster and higher than more complex carbs. But Emond cautioned that this is only one study—these findings will need to be replicated by future research.

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Now, I’d love to tell you that all you need to do is just avoid starchy carbs, but Emond said it’s not that simple. There are different types of starches, and depending on what else you eat with the starch—such as fiber, fat or protein—it can have varying effects on your insulin level. The next step in research, said Emond, is figuring out which types of starches and which food combinations may raise the risk for breast cancer more than others.

Future research will also need to address whether or not cutting back on certain starches might help women who have never had breast cancer reduce their risk for the disease.

In the meantime, Emond recommends that all breast cancer survivors (actually all cancer survivors) follow the dietary guidelines recommended by the American Cancer Society, which include eating mostly plant-based foods and high-fiber foods and avoiding refined grains (such as white bread, white rice, and cereals and crackers that don’t say “whole grain” on the package).