Polysaccharide starch or amylum is a carbohydrate consisting of a large number of glucose units joined together by glycosidic bonds produced by all green plants as an energy store. It is the most common carbohydrate in the human diet and in staple foods as potatoes, wheat, maize (corn), rice, oats, barley and cassava. Researchers have linked increased starch intake to a greater risk for breast cancer recurrence, according to results presented at the 2011 CTRC-AACR San Antonio Breast Cancer Symposium (SABCS), held December 6-10, 2011.

?The results show that it?s not just overall carbohydrates, but particularly starch,? said Jennifer A. Emond, M.S., a public health doctoral student at the University of California, San Diego. ?Women who increased their starch intake over one year were at a much likelier risk for recurring.?

Researchers conducted a subset analysis of 2,651 women who participated in the Women?s Healthy Eating and Living (WHEL) Dietary Intervention Trial, a plant-based intervention trial that enrolled about 3,088 survivors of breast cancer. All women were diagnosed with breast cancer within the previous 4 years.

WHEL researchers studied breast cancer recurrence and followed the participants for an average of seven years. The subset analysis involved an examination of how changes in carbohydrate intake influenced breast cancer recurrence. ?The WHEL dietary trial, even though it focused on fruits and vegetables, fiber and fat, didn?t really have a specific carbohydrate goal,? Emond said. Together with her colleagues Emond obtained carbohydrate intake information from multiple 24-hour dietary recalls at baseline and at one year. In an annual phone interview, participants reported everything they had eaten during the last 24 hours.

Increase in carbohydrate intake
At baseline, carbohydrate intake was 233 grams per day. Results showed that women whose cancer recurred had a mean increase in carbohydrate intake of 2.3 grams per day during the first year, while women whose cancer did not recur reported a mean decrease of 2.7 grams per day during the first year (2.3 vs. -2.7 g/day; p=0.188). Starches were particularly important, Emond said. Changes in starch intake accounted for 48% of the change in carbohydrate intake (R-squared: 48%; p<0.001). Baseline starch intake did not differ by recurrence status (95.8 g/day; p=0.219). Mean change in starch intake during the first year was ?4.1 grams per day among women whose cancer recurred vs. ?8.7 grams per day among women whose cancer did not recur (p=0.015).

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Changes in diet quality
When change in starch intake during one year was grouped into quartiles of change, the rate of an additional breast cancer event was 9.7% among women who decreased their starch intake the most during one year, compared with an event rate of 14.2% among women who increased their starch intake the most during one year. The change in starch intake was ?independent of dietary changes that happened in the intervention arm ([p=0.326]),? Emond said. ?It is independent of more global changes in diet quality.? In the adjusted model, a 5-g/day increase in starch related to a 3% increased risk of recurrence (HR=1.03; 95% CI 1.01 ? 1.06; p=0.017). The increased risk was limited to women diagnosed with low grade tumors.

After stratifying patients by tumor grade, Emond and colleagues found that the increased risk was limited to women with lower-grade tumors. These results indicate a need for more research on dietary recommendations that consider limited starch intake among women with breast cancer.

For more information:
Change in Carbohydrate Intake and Breast Cancer Prognosis.
Presenter: Jennifer A. Emond, M.S.
Abstract Number: P3-09-01

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