By Chandley Silin, RN, FNP-BC, AOCNP®
P.G. is a 54-year-old woman who presents to the infusion center to receive her second cycle of chemotherapy for breast cancer. As her oncology nurse, you check the chemotherapy orders and patient history and are concerned to see that her weight has dropped by 10% from baseline, necessitating a change in dosing.
You ask P.G. about the weight loss, and she tells you she has cut out all sugar and carbohydrates because she read online that “sugar feeds cancer.”
What Would You Do?
Oncology nurses and advanced practice providers serve as frequent points of contact and trusted sources of information for patients. Therefore, nurses have a responsibility to be cognizant of common misconceptions, particularly those that affect treatment outcomes, and able to counter them with evidence-based information.
Currently, no research directly supports the claim that sugar fuels the growth cancer. All cells in the body, including cancer cells, use sugar (glucose) for energy. Decreasing the amount of glucose eaten won’t decrease the amount used by any particular cell. However, excess sugar intake may indirectly increase an individual’s risk for developing and dying from cancer.
Here’s what the science tells us about the complex relationship between sugar and cancer: The link between obesity and many types of cancer, including uterine, colon, gallbladder, thyroid, breast, and kidney, is well established.
The physiologic process by which excess glucose leads to obesity is complex. After food is ingested, the pancreas secretes insulin in response to increased blood glucose, signaling the body to either use the glucose as energy or store it for later use. Excess glucose is stored as fat that, over time, can lead to weight gain.
Researchers have identified several mechanisms by which excess fat may possibly lead to cancer. In women, peripheral adipose tissue creates estradiol, a sex hormone that is linked to breast, endometrial, and ovarian cancer. Insulin resistance leads to an increase in circulating insulin and insulin growth factors. Fat cells (adipocytes) secrete inflammatory hormones called adipocytes, which may create changes in the cellular environment that favor a tumor’s development and growth.
We also know that patients with cancer who have hyperglycemia have worse outcomes during treatment, whether because of increased incidence of comorbidities like heart disease, increased susceptibility to infection, or more aggressive disease.
So, although eating sugar may not directly cause cancer, limiting added sugars (no more than nine teaspoons per day for men and six teaspoons per day for women) and maintaining a healthy weight can help prevent certain obesity-linked cancers. For patients with cancer undergoing treatment, especially those with baseline hyperglycemia, maintaining tight control of blood glucose levels can help prevent complications and may improve outcomes.
Oncology nurses can encourage patients undergoing chemotherapy to maintain a balanced diet and avoid excess weight loss, because malnutrition during treatment is associated with poorer tolerance and outcomes.