Cancer and Nutrition: 8 Common Myths Busted

GRYT Health was fortunate enough to have Krystle Zuniga, Ph.D., lead a program that went over the latest research on the relationship between nutrition and cancer.

As a registered and licensed dietician, Dr. Zuniga works as an oncology dietitian at LIVESTRONG Cancer Institutes.

This article is a text summary of her program that took place in March 2021. If you'd rather watch her hour-long program, you can watch below.


To kick things off: You are what you eat! It's important to remember that food is more than fuel for your body; you are literally made up of nutrients you consume. Your dietary choices impact your health.

Nutrition Guidelines for Cancer Survivors

If you're a cancer survivor and wonder what general guidelines you might follow to keep your body as healthy as possible, several organizations have come up with several things to follow.

Those organizations include:

  • American Cancer Society
  • American Institute for Cancer Research
  • American College of Sports Medicine
  • National Cancer Institute

The guidelines survivors should look to follow are:

  • Maintain a healthy weight
  • 150 minutes of moderate to vigorous physical activity a week
  • Healthy diet pattern rich in plant foods

Are these guidelines surprising? Not really. You've probably heard this kind of guidance back in grade school in your health class.

The following are 8 myths when it comes cancer and nutrition. Whether you're a cancer patient, survivor, or someone looking to decrease the chance of getting cancer, this information can help you have a balanced and safe diet.

Myth: Need to Follow an Organic, All-Natural, No Chemicals, Unprocessed, Whole Foods Diet

First - what does organic even mean? It doesn't relate to the nutritional value of the food. It relates to how that food is made.

  • What is allowed in organic farming:
  • Biological pest management
  • Crop rotations
  • Composting
  • Manure
  • Organic pesticides and fungicides

What isn't allowed in organic farming:

  • Synthetic pesticides
  • Antibiotics
  • Fertilizers
  • Hormones
  • Sewage sludge
  • Genetic engineering
  • Irradiation

Organic does not necessarily mean healthy! Organic cookies, chips, and other snacks can contain the same amount of calories, fat, and sugar as conventional brands! It's still important to look at nutritional labels, even if something is labeled as organic.

GMOs - genetically modified organisms - have a poor public perception. However, four large medical organizations have deemed GMOs to be safe. Those organizations include:

  • The World Health Organization
  • American Medical Association
  • National Academy of Sciences
  • American Association for the Advancement of Science

Consuming a diet rich in fruits and vegetables, whether grown conventionally or organically, can lower cancer risk.

Eating non-organic produce is better than not eating any produce at all.

There have been no human studies showing that organic foods are better in reducing the risk of cancer, recurrence, or cancer progression.

Labels on foods that might appear that makes the food healthier can often be deceptive. Many of these don't have clear definitions, meaning there aren't any guidelines that companies need to follow to slap these labels on their products! These labels include:

  • Natural
  • Organic
  • Cage-free
  • All-natural
  • No GMO
  • No artificial flavors or colors
  • No preservatives

Myth: Need to Regularly Detox or Cleanse Body

Guess what? Your body has natural detox systems in place - your liver, kidney, and skin are natural detox systems.

You should add foods to your diet - fruits and vegetables - to improve the function of these natural detox systems. This also includes adequate hydration as well as ensuring you get the right amount of nutrition.

Myth: Dietary Supplements Are Needed To Prevent Cancer Recurrence

The American Institute for Cancer Research does not recommend using supplements for cancer prevention. Instead of supplements, choose a balanced diet with a variety of foods to reduce the risk of cancer.

One caveat: vitamin D is becoming an intriguing vitamin in the role of cancer prevention. Studies are happening around this specific vitamin, but no hard evidence supports cancer prevention and recurrence.

If you are a cancer patient or survivor, there are some things to consider when taking supplements. Those are:

  • Supplements should not replace nutrient-rich foods in your diet
  • Supplements are not recommended for cancer prevention
  • More supplements does not mean more significant benefits
  • Review all supplement products you wish to take with your oncologist
  • "Natural" supplements does not mean they are safe to take

Supplements should only be a small slice of your foundation of nutrition for your body. That is, thinking about what you need to have in your diet for energy balance, what macronutrient needs you need to address with food, and the variety of foods you intake daily.

Myth: Sugar Feeds Cancer

First of all - what is sugar? Sugar is sucrose. Sucrose is glucose + fructose. All carbohydrates in our diet are broken down into glucose. Glucose is the primary source of energy that every single cell in our body uses for energy. In fact, red blood cells can only use glucose as a source of energy.

Sugar feeds every cell in the human body! Limiting sugar won't selectively "starve" cancer cells.

Eating high-sugar foods means you could be consuming too many calories. This means weight gain. And having an unhealthy weight does lead to increased cancer risk.

So limit refined foods with added sugars. These types of food sources are low in nutrients and high in calories.

The recommendation on sugar by the American Institute of Cancer Research is to:

  • Avoid sugary drinks.
  • Limit consumption of energy-dense foods.
  • Limit intake on foods and beverages that are high in refined carbohydrates, added sugar, and fat, as they contribute to obesity which is a significant risk factor for cancer.

Myth: Need to Eliminate All Animal Products

The American Institute for Cancer Research has a guideline about meat and recommends limited red meat to 12-18 ounces/week and avoiding processed meats.

There is no clear evidence that a vegetarian or vegan diet is more protective against cancer risk or recurrence.

Look to have a plant forward diet. A plant forward diet is rich in fiber, micronutrients, and phytochemicals. These foods promote natural detoxification with the systems in your body. And the more food variety you can introduce in your diet, the better.

Myth: Avoid Soy and Soy Products

Soy contains several vital nutrients and phytochemicals shown to protect against cancer.

A moderate amount of soy foods may lower the risk for breast cancer and recurrence.

A moderate amount = 1-2 servings a day. Avoid soy isoflavone supplements or concentrate forms of soy protein.

Myth: Need to Eat Exotic and Expensive Superfoods

There are no miracle foods. Foods that can "kill cancer" or "cure cancer" do not exist.

Phytochemicals are healthy for your body. These are commonly found in plants and foods such as broccoli, garlic, green tea, honey, soybeans, cabbage, ginger, grapes, chili peppers, tomatoes, and more. Phytochemicals are anti-oxidant, anti-inflammatory, anti-carcinogenic, and anti-viral. They are not essential for your body but provide many benefits.

Myth: Need to Follow A Strict Diet

A keto diet has limited and low-quality evidence for cancer prevention or recurrence.

Same with intermittent fasting: there is limited and low-quality evidence that this diet prevents cancer or cancer recurrence.

Focus on the foundations of healthy eating. This can mean getting enough calories or hydration in your daily intake.

Set realistic goals! A goal could be, "I want to cook dinner four times this week."

Nutrition is an essential tool in your well-being, but other things play into your health as a human! Those other factors include hydration, getting enough sleep each night, physical activity, stress management, and more.

Nutrition Regulations Are Young

It takes so much research to change things in the nutrition industry. A couple of things that seem like they've been in place forever that shows how young regulations are:

  • The first dietary guidelines were in place in 1983.
  • The first food label regulations started in 1991.
  • Dietary supplement regulations began in 1994.

You can find Dr. Krystle Zuniga at @real.nutrition.science or her cancer-focused profile @cancernutritionhq on Instagram 

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