Five Nutrition Myths About Cancer, Debunked by an MSK Doctor

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Five nutrition myths debunked

Smoking, sun exposure, and genetics are widely recognized as factors that can increase cancer risk. But one of the most misunderstood, and often debated, areas of cancer research? Our diets. Every day, a flurry of headlines suggest that what we eat can both raise and lower our risk of cancer. With so much information circulating comes the inevitable misinformation — making it harder than ever to parse fact from fiction.

Enter Urvi Shah, MD, a medical oncologist at Memorial Sloan Kettering Cancer Center (MSK) who specializes in treating people with myeloma, a category of blood cancers. Like most doctors, she wasn't trained to consider nutrition when it came to her practice. Then came her own devastating diagnosis, a year into her fellowship: she had Hodgkin lymphoma, the very same disease she was studying. "Friends and family began offering advice on what to eat and avoid," she recalls, "and it became clear that I did not know enough about modifiable risk factors within our control."

Today, Dr. Shah leads nutrition-based clinical research at MSK, focused on how dietary patterns may influence cancer risk. Her work includes the NUTRIVENTION trials, which examine whether a high-fiber, plant-forward diet can impact key cancer risk markers — such as metabolism, inflammation, and the gut microbiome — in patients with precancerous conditions. The program has since expanded to multiple trials that will collectively enroll nearly 600 patients, helping researchers better understand the role nutrition may play in cancer prevention and progression.

With this science-backed research on her side, Dr. Shah helps unpack five common myths about diet and cancer — and what the evidence really says.

Myth #1: You need animal protein because plant proteins are incomplete

“Many people believe animal protein is necessary because plant proteins are incomplete, but all plant foods contain the amino acids the body needs, and a varied plant-based diet can meet protein requirements. Red and processed meats are often viewed simply as protein sources, yet strong evidence shows they are associated with increased cancer risk. The International Agency for Research on Cancer classifies processed meats as ‘definitely carcinogenic’ and red meat as ‘probably carcinogenic,’ while plant proteins provide protein, fiber, and protective nutrients — and can help reduce cancer risk.”

Myth #2: You should avoid all carbohydrates if you have cancer

“Carbohydrates, especially those rich in dietary fiber, play an important role in overall health—as well as cancer outcomes. Fewer than 5% of people in the United States consume enough fiber, even though foods like beans and legumes provide both fiber and protein. The real issue is the type of carbohydrate: Refined sugars and processed foods may potentially increase cancer risk, while whole grains, fruits, and vegetables provide fiber and protective nutrients, and may help reduce risk.”

Myth #3: You should only eat organic fruits and vegetables

“Eating more fruits and vegetables — organic or not — is an effective way to help reduce cancer risk. The health benefits of eating produce far outweigh the potential risks from pesticide exposure. The most important goal is to eat more fruits and vegetables, regardless of how they are grown.”

Myth #4: Diet can’t meaningfully change the gut microbiome during cancer

“Many people think the gut microbiome is fixed or too damaged by cancer or its treatment to change, but studies suggest that greater gut microbiome diversity is linked to better cancer outcomes — and diet is one of the strongest influences on this diversity. Fiber-rich plant foods, fermented foods, and eating a wide variety of plants can support a healthier microbiome.”

Myth #5: Soy increases breast cancer risk

“Soy foods contain plant compounds that resemble estrogen, but they act differently in the body. Research suggests that eating whole soy foods like tofu, edamame, and soy milk is safe and may even lower the risk of breast cancer recurrence. Highly processed soy foods such as soy protein isolate are less studied and may be avoided in large quantities.”