Dispelling Nutrition Myths for Patients With Cancer

Oncology Nursing NewsAugust 2022
Volume 16
Issue 4

Entering the words nutrition and cancer into Google returns as many as 718 million hits. With an overabundance of opinions, it can be challenging to separate fact from fiction.

Myth No. 1: Sugar Feeds Cancer

Sugar gets a bad rap, no bones about it. The American Institute for Cancer Research recommends individuals reduce the amount of sugar-sweetened beverages and foods with added sugar in their diet as a way to help prevent cancer.1 When a diet is concentrated in sugar, it usually lacks the fruits, vegetables, and phytonutrients our bodies need. However, it is important to remember that sugar is not the sneaky spy it is projected to be. Sugar cannot discern which cells are cancerous and then exclusively feed only those; it will feed all the cells in the body. Individuals who reduce their sugar intake during treatment and consequently lose weight may cause additional harm to their body. Unintended weight loss as small as 5% increases a patient’s risk of mortality.2,3

Further, many patients may be under the impression that if they are overweight they cannot be malnourished. However, unintentional weight loss as small as 5% over 6 months is a risk factor for precachexia.2,3 Sarcopenic obesity is frequently overlooked because the patient has a mantle of fat masking decreased muscle reserves.3 This is a classic case of how the cover of a book can be misleading. Survival times can be shortest among those with obesity and sarcopenic weight loss.3 Meeting with a dietitian early during treatment can help patients correct early weight loss before it leads to more significant impacts, such as treatment delays.

The Bottom Line: Once a patient has received a diagnosis of cancer, they should maintain their intake of fruits, vegetables, and phytonutrients and avoid losing unexpected weight. Decline in quality of life and survival can occur with weight loss as small as 5%.

Myth No. 2: Soy Must Be Avoided After a Breast Cancer Diagnosis

Just ask anyone who has breast cancer: The word soy stirs all kinds of emotions. However, real soy foods such as tempeh, tofu, edamame, and miso are different from their highly processed cousin, soy protein isolates.3,4 Many studies show that consuming whole soy foods can reduce the risk of cancer.5

In a recent meta-analysis from April 2022, consumption of soy isoflavones was found to reduce the risk of breast cancer in both premenopausal and postmenopausal women.6 It’s just another reason to stop the soy fear and consider using whole soy foods as a plant-based protein option.

The Bottom Line: Whole soy foods (edamame, tofu, tempeh, miso, etc) can reduce the risk of cancer.

Myth No. 3: Patients With Cancer Should Become Vegan and Eat Only Organic Foods

Following a vegan lifestyle for survivorship benefit is much like the square and rectangle rule we learned in school. A square is always a rectangle, but a rectangle is not always a square, right? A vegan lifestyle can be a healthy lifestyle providing survivorship benefit for some individuals. But a vegan lifestyle is not necessarily recommended for everyone. Eating plants (fruits, vegetables, whole grains, nuts, seeds, and beans) takes priority over organic, vegan, paleo, or vegetarian lifestyles.1,3

To become a certified organic farmer, a farm must submit applications, pay fees, and undergo routine testing.7 All these requirements increase cost, which is typically offset by the consumer. Research does show relatively small differences in polyphenol compounds and vitamin content when comparing organic and inorganic foods. These differences, however, appear to be insignificant and have yet to show a change in patient outcomes.3,8

The Bottom Line: Eating more plants is the priority.

What Can Dietitians Do to Help?

Patients and providers alike have a perception of what a dietitian should be or what a dietitian offers. As a result, both nurses and patients often put up barriers, telling themselves they already know what to do. The reality is that dietitians have so much to offer. They are not here to judge what or how a patient eats. Most of them came into this profession to help others. The training they’ve received helps them pick up subtle clues that can make a big difference in how patients feel or tolerate treatment.

Many patients’ symptoms can be improved by making simple changes in what and how they eat. Dietitians who are board-certified specialists in oncology nutrition are trained to look for signs of malnutrition and treatment-specific adverse effects.

The Bottom Line: Take advantage of having an oncology dietitian on your team (the sooner the better!). Nutrition as a science constantly changes and evolves. As dietitians, we do our best to stay updated on the changing trends, research, and practical applications.


1. How to prevent cancer: 10 recommendations. American Institute for Cancer Research. Accessed June 16, 2022. https://bit.ly/3N0EmXX

2. ONC: nutrition and the adult oncology patient. Academy of Nutrition and Dietetics Evidence Analysis Library; Oncology Guidelines. 2013. Accessed June 16, 2022. https://bit.ly/3MX4Qtd

3. Voss AC, Williams V, eds. Oncology Nutrition for Clinical Practice. 2nd ed. Academy of Nutrition and Dietetics. 2021:24-25,59.

4. 10 myths about breast cancer survivorship. Johns Hopkins Medicine. https://bit.ly/3MX4l2A

5. Douglas CC, Johnson SA, Arjmandi BH. Soy and its isoflavones: the truth behind the science in breast cancer. Anticancer Agents Med Chem. 2013;13(8):1178-1187. doi:10.2 174/18715206113139990320

6. Boutas I, Kontogeorgi A, Dimitrakakis C, Kalantaridou SN. Soy isoflavones and breast cancer risk: a meta-analysis. In Vivo. 2022;36(2):556-562. doi:10.21873/invivo.12737

7. McEvoy M. Organic 101: five steps to organic certification. US Department of Agriculture. December 14, 2020. Accessed June 16, 2020. https://bit.ly/3QplhSe

8. Cordeiro B. Do GMOs cause cancer? The University of Texas MD Anderson Cancer Center. June 2014. Accessed June 16, 2022. https://bit.ly/2Bk4mM7

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