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Dear Dietitian – Nutrition myths and cancer

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PICT Leanne McCrate Dear Dietitian
Leanne McCrate, RDN, LD, CNSC

Dear Readers,

Today I am writing about a topic near and dear 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. Choose mono- and polyunsaturated fats. 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 nutrition quackery.  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.

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These are just a few myths involving nutrition and cancer:

  1. Sugar feeds cancer.  This statement 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. There is no scientific research to support the previous statement. The truth is our bodies must have glucose to survive.  If we don’t consume it in our diet, our bodies will make glucose from fat or protein in a process known as gluconeogenesis.
  3. Consuming an alkaline (high pH) diet will cure cancer. Supposedly, alkaline foods (including baking soda) and alkaline water neutralize a cancer-friendly acidic environment.  The truth is the pH of our blood is always slightly alkaline. It doesn’t matter what the pH of your food or drinking water is; your body will always maintain a pH balance of about 7.2.
  4. Vitamin D prevents cancer.  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 the risk for pancreatic or aggressive prostate cancers.”
  5. An all-vegetable diet cures cancer. While there is some evidence that the nutrients found in vegetables may help prevent certain cancers, there is no scientific research supporting that vegetable consumption will aid in a cure.   

While nutrition is a vital aspect of cancer treatment, there is no nutritional cure for cancer.  It is important to stay well-nourished to help maximize the outcome of cancer treatment. Registered Dietitian Nutritionists (RDNs) are available wherever you receive cancer care to help you maintain a healthy nutritional status. My goal is to help you make informed decisions where nutrition is concerned.


Dear Dietitian

Leanne McCrate, RDN, LD, CNSC, is an award-winning dietitian based in Missouri.  Her mission is to educate consumers on sound, scientifically-based nutrition.  Do you have a nutrition question?  Email her at Dear Dietitian does not endorse any products, health programs, or diet plans.