Dear Dietitian – nutrition myths and cancer

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Published Saturday, March 16, 2019
PICT Leanne McCrate Dear Dietitian
by Leanne McCrate, RD, LD, CNSC

Dear Readers,

Today I am writing about a topic near to my heart: nutrition and cancer, or more pointedly, nutrition myths and cancer. My clinical experience included twelve years of oncology nutrition, in both inpatient and outpatient settings. Good nutrition can help prevent some types of cancer, and not surprisingly, it is the same diet that helps prevent other diseases, such as heart disease and stroke.  You've heard it before and read it in this column: Eat lots of fruits and vegetables, whole grains, and lean proteins. Eat more plant foods.

Conversely, there is a lot of misinformation on nutrition, especially when it comes to cancer. Cancer patients are sometimes afraid and vulnerable, which may make them susceptible to quack nutrition.  Remember we live in a "let the buyer beware" society, and there is nothing in the First Amendment that requires free speech to include the truth.

These are just a few myths involving nutrition and cancer:

  1. Sugar feeds cancer.  This is misleading.  The real question is "Does sugar make your cancer worse?"  The answer is no.
  2. A ketogenic diet does not involve glucose (sugar) and so starves the cancer tumor.  The truth is our bodies must have glucose in order to survive.  If we don't consume it in our diet, our bodies will make glucose from fat and/or protein in a process known as gluconeogenesis -- a fancy name for making new glucose.
  3. Alkaline water/diet - similar to the baking soda myth.  Supposedly, alkaline foods (including baking soda) and water neutralize a cancer-friendly acidic environment.  The truth is the pH of our blood is slightly alkaline.  Mechanisms are in place to keep this in place; otherwise, the human body cannot survive. It doesn't matter what the pH of your food or drinking water is, your body will always maintain a blood pH balance of about 7.2.
  4. Vitamin D. According to Memorial Sloan-Kettering Cancer Center, an internationally renowned facility in New York: "Intake of vitamin D through diet may protect against breast or colorectal cancers or affect markers for prostate cancer.  However, vitamin D by itself does not prevent or treat cancer.  Other large studies show that high vitamin D levels do not reduce the risk of many other cancers, and may increase risk for pancreatic or aggressive prostate cancers."
  5. An-all vegetable diet.  There was a patient in the hospital that revealed she had followed an all-veggie diet for cancer, and exclaimed, "I lost 30 pounds, and it was all muscle!"  A vegetables-only diet will leave you malnourished and dissatisfied, and on no uncertain terms, will not improve a cancer diagnosis.

While nutrition is a very important aspect of cancer treatment, there is no nutritional cure for cancer.  It is important to stay well-nourished in order to help maximize the outcome of cancer treatment. Registered Dietitians (R.D.s) are available wherever you receive cancer care to help you maintain a healthy nutritional status. My goal is to help you make informed decisions when nutrition is concerned.


Dear Dietitian

Leanne McCrate, RD, LD, CNSC, is an award-winning dietitian based in Missouri.  Her mission is to educate the public on sound, evidence-based nutrition.  Do you have a nutrition question?  Email her at may earn an affiliate commission if you purchase products or services through links in an article. Prices, when displayed, are accurate at the time of publication but may change over time. Commissions do not influence editorial independence.

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