Dear Mayo Clinic: Food risks and cancer: What to avoid

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Photo of ingredients for a salad, including lettuce, chickpeas and avocadoes

DEAR MAYO CLINIC: I was recently diagnosed with cancer. Are there specific foods I should be eating or avoiding?

ANSWER: It's not about any one food, and it's not about one diet; it's about a dietary pattern. The dietary pattern that organizations such as the American Institute for Cancer Research and the American Cancer Society recommend is a whole-food, plant-predominant diet. The whole food component is very important to emphasize — eating foods as close to nature as possible is key, not ones made in a factory. Aim to arrange half of your plate with a diverse array of colorful vegetables and fruits, a quarter from whole grains, and the rest from healthy sources of protein, especially from plant sources.

The average American consumes at least 63% ultraprocessed foods. Ultraprocessed foods are factory-manufactured, packaged foods (frozen pizza, microwave meals, chips, pastries, cupcakes, muffins, processed meat, sugar-sweetened beverages). These foods often have ingredients that are hard to pronounce. Studies show consumption of ultraprocessed food is linked directly to premature mortality or deaths from all causes. Cancer studies done in countries that don't consume nearly the amount of ultraprocessed foods compared to Americans show that not only do the ultraprocessed foods increase the risk of cancer occurring, but after a cancer diagnosis, these foods increase the risk of mortality. When you eat ultraprocessed foods, you're taking away the opportunity for your body to get nutrient-dense foods with vitamins, minerals, phytonutrients and fiber that can help fight cancer and keep it away. 

Processed meat, which often includes hot dogs, deli food and sausage, is categorized as a Group 1 carcinogen by the World Health Organization. To protect yourself against cancer, studies show that it would be best to avoid those foods. For your sources of protein, eat foods such as tofu, edamame, tempeh, fish, poultry and pulses.

What are pulses? Pulses are edible seeds from a legume plant. They include things such as lentils, peas and beans (black, pinto, kidney, chickpeas, etc.). Not only are you replacing animal protein when you consume pulses and soy, but you'll also get a lot of fiber. And in the U.S., there's not a protein deficiency but a fiber deficiency. Soy foods are safe for all cancer patients and are an excellent source of plant protein. Studies show soy may improve survival after breast cancer.

Fiber is an essential nutrient, but only 5% of Americans get enough. A recent meta-analysis from the American Institute for Cancer Research Global Cancer Update Program showed that for every 10-gram increase in fiber in the diet, survival after breast cancer diagnosis improved by 13%. Health benefits of fiber include improved cholesterol, blood sugar regulation, gut health and digestion and weight control. Additionally, nuts and seeds have healthy, fatty acids that your body needs and are a great source of fiber and protein. But they are also calorie-dense, so be mindful of the serving size.

Aim to cut out ultraprocessed foods and consume mainly whole, plant-predominant foods:

  • A wide variety of colorful vegetables and whole fruit (not fruit juice).
  • Whole grains, such as steal cut oats, quinoa, brown rice and barley, to name a few.
  • Proteins from nonanimal sources.
  • Foods that aren't made in a factory.
  • Drink water, not sugar-sweetened beverages.

You can have a role in your cancer journey when you think of food as medicine, and that's exciting and empowering. —  Dr. Dawn Mussallem, Integrative Medicine and Health, Mayo Clinic, Jacksonville, Florida

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A version of this article was originally published on the Mayo Clinic News Network.