The Role of Diet in Cancer Prevention, Treatment, and Survivorship
Understanding how diet and nutrition support patients through the cancer care continuum
Reviewed by: Krystle Zuniga, PhD, RD, LD
Written by: Abbi Havens
UT Health Austin registered dietitian Krystle Zuniga, PhD, RD, LD, has made a lasting impact in caring for cancer patients in UT Health Austin’s Livestrong Cancer Institutes. While getting her doctorate in nutritional sciences at the University of Illinois Urbana-Champaign, Dr. Zuniga used animal and cell culture research to study the effect of dietary interventions for prostate cancer prevention all the while researching the role of diet and exercise on brain health in cancer survivors.
“With my research, my private practice, and as a professor, I’ve always been involved in the community presenting to cancer support groups about diet and cancer,” says Dr. Zuniga. “When the Livestrong Cancer Institute developed its CaLM care model and this whole-person approach to treating cancer, which I deeply believe in, I knew that nutrition needed to be a key element of what was happening at the Livestrong Cancer Institutes, and I knew I wanted to be a part of it.”
In her role, Dr. Zuniga has the opportunity to bridge research and clinical care using diet and nutrition to support patients through a cancer care continuum from cancer prevention to cancer treatment and cancer survivorship.
Nutrition and Cancer Prevention
The more research surrounding the impact of diet on the risk of developing cancer improves and evolves, the more we know about the power you have to take your health into your own hands through the food you eat, and that’s something to get excited about.
“Research consistently shows that a diet that is primarily plant-based with limited red and processed meat is correlated with reduced incidence of cancer, heart disease, and diabetes. If you follow this diet, you not only reduce your risk of developing cancer, you also reduce the risk of developing other chronic diseases,” says Dr. Zuniga.
Some confusion (and some controversy) surrounds the phrase plant-based. In fact, the words themselves may elicit an eye roll from many. But contrary to popular belief, the dietetic definition of plant-based is not fully-restrictive, and it’s not synonymous with vegetarianism or veganism. According to Dr. Zuniga, plant-based simply means that the majority of your diet is derived from fruits, vegetables, grains, nuts, seeds, and legumes. Plant-based diets limit your intake of animal products, particularly red and processed meats, but these foods do not have to be eliminated entirely. Patients should focus on whole foods and meat should be treated as an accessory to your meal, not the main attraction.
Before you dismiss the plant-based diet, Dr. Zuniga wants you to know that creating a healthy diet that aids in the prevention of cancer doesn’t mean you can never eat a steak again. Research surrounding diet and cancer used to focus on whether or not certain foods and food groups contribute to a person’s risk of developing cancer later in life. Now, that focus has shifted away from individual foods and towards dietary patterns and a patient’s overall nutritional status.
“It’s easy for people to become obsessed with determining which foods are ‘good’ and which foods are ‘bad,’ to the point where it becomes unhealthy and unproductive,” says Dr. Zuniga. “Just focus on whole foods, fruits, vegetables, and lean protein, and you’ve got a good foundation for prevention.”
Dr. Zuniga recommends referring to the American Institute for Cancer research for more information on cancer prevention through diet and lifestyle, which includes a library of healthy, whole-food recipes packed with superfoods.
Nutrition During Cancer Treatment
Let’s get one thing straight. Diet should not be regarded as a cure for cancer, but rather a tool to support cancer treatment and the overall nutritional status of a patient. Regarding diet as a cure for cancer can have detrimental effects.
“Unfortunately, I’ve seen patients who opted out of cancer treatment in favor of a natural and diet-based approach to ‘curing’ cancer,” says Dr. Zuniga. “There is no evidence that a particular diet pattern or food can cure cancer. Opting out of treatment can result in disease progression.”
Patients are often surprised to hear Dr. Zuniga’s dietary recommendations during cancer treatment because they may contradict recommendations for a preventative diet, but there’s a reason for this. Any steadfast diet during cancer treatment, particularly chemotherapy, can be nearly impossible to adhere to. The sight of an apple or the smell of broccoli might nauseate a patient, so a largely plant-based diet may not be practical during this time. Instead, it’s important for patients to do what they can to keep on weight and go easy on themselves.
Chemotherapy has many side effects, including nausea, vomiting, diarrhea, loss of appetite, and mouth, sores which make eating difficult and painful. These side effects often lead to unintentional weight loss. Unintentional weight loss includes loss of muscle mass. Loss of muscle mass often results in low cancer treatment tolerance and poor outcomes. Dr. Zuniga’s dietary focus, when it comes to patients undergoing cancer treatment, is all about maintaining weight and nutritional status.
“We know if you’re adhering to your cancer treatment plan, you’re going to have better outcomes, so that is my primary focus during cancer treatment. My strategies often sound counterintuitive to what I promote for prevention, because I tell patients to eat high calorie foods and eat whatever they can to maintain their weight during treatment” ays Dr. Zuniga. “If a patient has a low appetite during cancer treatment, it’s okay to eat a slice of pizza instead of a cup of broccoli. They’re going to get a lot more bang for their buck calorie-wise than if they try and fail to fill themselves up with low calorie foods and beat themselves up about it later.”
Chemotherapy may cause a patient’s white blood cell count to drop, which means food safety is extremely important during this time. Patients should thoroughly wash all produce before consumption, avoid raw fish, and cook all meat to a minimum of 160°F. Patients should also avoid taking supplements of any kind before discussing them with their care team during cancer treatment. Some supplements, particularly those with high doses of antioxidants, can negatively affect the efficacy of cancer treatments. For example, probiotics which introduce new bacteria to your system, as cancer treatment often compromises the intestinal barrier and intestinal health.
Patients experience a significant amount of fear around food during cancer treatment. Dr. Zuniga wants patients to know that instead of worrying which foods will progress their cancer, they should see food as a pillar of support to get through treatment.
“Patients should look at nutrition as a way to support them and support treatment efficacy. Rather than alternative medicine, I consider diet complimentary and integrated with the comprehensive approach to cancer treatment,” says Dr. Zuniga. “There are many things needed to support you during cancer treatment, and diet is one of them.”
Nutrition and Cancer Survivorship
While research does not definitively show that diet alone can prevent the return of certain cancers, research does support a majority plant-based diet for reducing the risk of developing cancer overall, and this applies to survivorship.
Although a healthy diet for cancer survivorship largely resembles that of a preventative diet, the difference is that in the survivorship phase, patients may need to lose weight or regain weight and put on lean muscle mass that was lost during treatment. Based on patients’ personal needs and their experience during treatment, Dr. Zuniga helps patients customize and evolve their diet post-cancer treatment as they recover.
“It’s a lot for patients to navigate, and the ability to be here as a resource for patients and guide them through this difficult time is where I get a lot of enjoyment in my job. They don’t have to go through this alone,” says Dr. Zuniga.
In every phase of a person’s relationship to cancer, whether it’s prevention, treatment, or survivorship, it’s easy to be inundated with misinformation. The internet is full of forums serving as a platform for people, while well-intended, who lack medical education, spreading misinformation about what foods do or don’t cause cancer, what strict diet one must adhere to, and so on. These pseudo-facts only confuse, overwhelm, and terrify patients, sometimes even putting their health at risk. Dr. Zuniga’s role is to simplify and demystify nutrition’s relationship to cancer and identify attainable ways for patients to achieve better outcomes.
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