If you research “cancer and nutrition,” you’ll find an almost endless amount of content. But can you separate fact from fiction? Corey Tolbert, RD, LD, a licensed and registered dietitian at Cancer Wellness at Piedmont, shares the most common cancer nutrition myths she hears from patients—and tells us where to find reputable information instead.
Myth: Sugar feeds cancer cells
“Sugar doesn’t feed cancer cells—everything you eat feeds all of your cells,” says Tolbert.
All foods are broken down into some form of sugar in the body. Carbohydrates are converted to glucose, fruit to fructose and dairy to lactose.
Tolbert says many of her patients tell her they are restricting carbohydrates and sugar, but she warns they could be missing calories and nutrients from healthy sources like complex carbohydrates (such as sweet potatoes, quinoa, oatmeal and fresh fruit). She says it’s crucial to consume enough calories during cancer treatment so your body can stay strong.
That said, cutting back on added sugar, “table sugar” and processed or refined carbohydrates is a good idea.
“Consuming too many refined and processed carbohydrates can lead to inflammation and obesity, which are both risk factors for cancer and recurrence,” says Tolbert.
Myth: An alkaline diet fights cancer
“The main thought behind the alkaline diet is the myth that acidic diets cause cancer,” she explains. “The goal with these diets is to put your body into an alkaline state. However, the body’s normal pH is naturally 7.4. Your diet can’t manipulate your body’s pH because your lungs and kidneys do that for you.”
In other words, if you try to eat your way to an “alkaline state,” you could be doing yourself harm because your lungs and kidneys will need to work in overdrive to get you back to that ideal 7.4 pH.
Myth: Soy causes breast cancer
Tolbert says soy gets a bad rap because researchers initially believed it could increase estrogen in the body and, therefore, women with estrogen-positive breast cancer could increase their risk of recurrence.
“These findings were proven to be inaccurate,” she says. “It’s been shown that a moderate amount of soy—one to two servings per day—doesn’t increase the risk of breast cancer recurrence. It actually reduces the risk.”
This is because soy is broken down into isoflavones, which can act as blockers to estrogen receptors.
“Basically, the isoflavones you get from pure soy are actually cancer-fighting,” says Tolbert.
She says if you eat soy, it’s essential to choose whole-food sources, like edamame, soy nuts and tofu, and avoid processed soy foods, like soybean oil and powders.
Myth: Supplements help fight cancer
Tolbert says most supplements are unnecessary, with a few caveats.
“By eating a well-balanced diet, you should be able to get what you need from a nutrient standpoint,” she says. “Supplements can interact with certain treatments, which can be toxic.”
However, if you’re having trouble eating enough or keeping food down during treatment, you may need a multivitamin. If you don’t consume much fish or omega-3 fatty acids, ask your doctor or dietitian about a fish oil supplement. And if you don’t regularly eat probiotic-rich foods, Tolbert recommends taking a probiotic supplement.
She also cautions that supplements aren’t regulated by the Food and Drug Administration (FDA). If you are going to take supplements, she recommends selecting a brand with a USP or NSF verification on the label.
Myth: Juicing can reduce the risk of cancer
“Juicing isn’t a bad thing to do,” says Tolbert. “You get nutrients from juice, but you also miss out on fiber and nutrients from the pulp.”
Juicing is OK as part of a healthy diet, but she cautions against doing juice fasts because you won’t consume enough calories and fiber.
Should you eat organic foods to prevent cancer?
“If you can get organic foods, I think it’s beneficial,” says Tolbert.
If you’re on a budget, she recommends focusing on organic animal products, like meat, poultry, eggs, cheese and milk. When shopping for fruits and vegetables, you can consult the Environmental Working Group’s Dirty Dozen and Clean 15 lists, which indicate produce that contains the most and the least amounts of pesticide residue.
“You can also wash tough-skinned produce with one part white distilled vinegar and three parts water,” she says. “Anything you can do to decrease your exposure to pesticides is a good thing.”
Foods to avoid to reduce your risk of cancer
Tolbert recommends limiting or avoiding refined sugar, processed foods and nitrates (found in bacon, sausage and other cured meats).
The best foods to prevent cancer and recurrence
“Overall, you want to have well-balanced meals and increase your plant-based eating,” she says. “By increasing the amount of plant-based foods you consume, you’ll increase phytochemicals, which neutralize damage to the body’s cells and support your immune system.”
Where to find trustworthy nutrition information
If you would like to do more research on cancer and nutrition, Tolbert recommends the following resources:
Learn more about nutrition for cancer survivors.