Nutrition and Cancer: Busting Common Myths

September 2019 Vol 10, No 9



A healthy diet may help to prevent cancer, inhibit cancer growth, and lower the risk of cancer recurrence, according to Natalie Ledesma, MS, RD, CSO, Clinical Nutrition Specialist at UCSF Helen Diller Family Comprehensive Cancer Center in San Francisco.

At the AONN+ 2019 Midyear Conference, Ms Ledesma shared her insight on what should constitute a healthy diet in patients with cancer and separated some common nutrition myths from facts.

“One of the myths patients sometimes face is, they’re told by practitioners to eat whatever they want, because it’s not going to matter,” she said. “I’m not saying we’re going to use diet to cure cancer. But to think that what’s fueling the body is going to have zero impact on cancer and on the risk for a variety of chronic diseases, as well as on a patient’s immune function, energy, and ability to get through treatment, is absolutely ludicrous.”

Essentials of a Healthy Diet

She said if she had to sum it up simply, these would be the basics: Ideally, patients with cancer should derive at least 80% of their nutrients from healthful plant-based sources and should strive for 8 to 10 colorful fruit and vegetable servings daily, in addition to 30 to 45 grams of fiber daily. They should limit their intake of processed and refined grains, flours, and sugars, as well as dairy and fatty/processed meats.

Such a diet helps patients to achieve 2 goals: upping their intake of vitamins, minerals, dietary fiber, and phytochemicals that can provide protective benefits against cancer and other chronic diseases. In addition, feeling satiated from these types of foods leads to lower consumption of animal fats and animal protein, processed foods, and sugars. One study found that women who consumed 5 or more servings of vegetables and fruits daily, in conjunction with 30 minutes of walking 6 days a week, had a significantly lower risk of death after early-stage breast cancer. Ms Ledesma noted that even modest changes in diet and lifestyle can have a significant effect on patient outcomes.

Patients should consume lean protein with every meal (including plant protein), and should opt for healthy fats from cold-water fish (ie, salmon, trout, herring, and sardines), nuts, and seeds (walnuts, olive oil, avocados, and almonds).

Herbs and spices (ie, turmeric, cayenne, rosemary, and basil) are healthy sources of antioxidants, and patients should consume them daily. Flax and chia seeds (1-2 tablespoons daily) can help with gastrointestinal motility, and green tea (1-4 cups daily) should serve as a good source of polyphenols.

All patients (but particularly those with gastrointestinal or breast cancer), should limit alcohol consumption and should engage in daily physical activity—even just a short walk—to help achieve and/or maintain a healthy body weight.

Is Sugar the Enemy?

Many of us have heard the myth that sugar causes cancer. Although there is no scientific evidence that sugar leads to cancer, the truth of the matter is, it’s not healthy.

If a food is high in added sugar, it is usually devoid of nutrient value. Additionally, the way that sugar is processed (particularly high-fructose corn syrup) appears to lead to higher fat mass and metabolic disease.

Sugar also leads to a relentless biochemical drive to consume more. Simply put, if you eat a lot of sugar, you’ll only want more. This increased consumption can lead to higher insulin levels, higher concentrations of insulin-like growth factors, and higher abdominal fat, which may be associated with an increased risk for various cancers. Also, hyperinsulinemia is associated with increased risk of heart disease, type 2 diabetes, a compromised immune system, and obesity.

The problem is that approximately 80% of food items in US grocery stores are spiked with added sugar. As a result, it is estimated that about one-third of Americans will have diabetes by the year 2050.

But as Ms Ledesma pointed out, it is human nature to want what we can’t have. Instead of telling patients not to consume sugar, she focuses on making sure they’re getting enough healthy foods in their diet: vegetables, fruits, beans/legumes, nuts/seeds, whole grains, and lean protein sources.

“My general focus with sugar is, do we have evidence that it causes cancer? No. Do I want to encourage patients to eat as much sugar as they want? No,” she said. “Rather than focusing on what they can’t have, instead focus on loading up their bodies with nourishing foods. Oftentimes, if they’re satiated, they don’t crave that added sugar.”

Another myth is that artificial sweeteners are a healthier alternative to sugar. Data have been inconclusive regarding the relationship between artificial sweeteners and cancer, but those who consume artificial sweeteners generally gain more weight than those consuming caloric sweeteners, potentially leading to a host of other challenges. And just like sugar, sweeteners perpetuate the desire for more sweets and may lessen satiety response.

Not a Myth: Inflammation and Cancer Risk

The association between inflammation and cancer, however, is no myth. Inflammation is linked to cancer as well as virtually every other chronic disease. According to Ms Ledesma, 2 key inflammatory biomarkers—C-reactive protein and fibrinogen—should be measured regularly in patients, as both have demonstrated a negative association with survival in clinical trials. But a balanced diet, especially one high in omega-3 fatty acids, can combat inflammation.

Whereas most American diets contain an excessive amount of omega-6 fats (ie, dairy, grain-fed meats, and corn oil), a diet rich in omega-3 acids can restore the balance between the 2 fatty acids and inhibit inflammation, thereby possibly reversing these disease processes.

There is no one-size-fits-all diet for patients with cancer, and nutrition should be personalized to each patient. Yet another myth is that all patients should follow a low-fat diet. That might be beneficial for some patients, but in others this equates to increased carbohydrate consumption, higher blood sugar levels, and weight gain. Nutrigenomics is a relatively new philosophy that focuses on a person’s genetics and uses biomarkers and other clinical data to, in turn, personalize their diet. “Nutri­genomics is here, and it’s real,” she said.

Perhaps most importantly, taking control of their own nutrition is empowering to patients and gives them a sense of control during an incredibly difficult time. According to Ms Ledesma, teaching patients about proper nutrition can possibly improve their clinical outcomes, but it will hopefully improve their quality of life.

Related Articles
Malnutrition in Patients with Cancer: An Often Overlooked and Undertreated Problem
Abby C Sauer, MPH, RD
February 2014 Vol 5, No 1
Patients with cancer face many challenges, including eating well to maintain a good nutritional status and avoid weight loss and malnutrition.
Last modified: August 10, 2023

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