Flawed Breast Cancer, Fruit and Vegetable Study

It was widely reported this week that a diet high in fruits and vegetables provided no added benefit against breast cancer recurrence. In this study published in JAMA, more than 3,000 women (average age 53) who were treated successfully for early stage breast cancer were followed for 6-11 years. Breast cancer recurrence rates were no better for those women who consumed 9 or more daily servings of fruits and vegetables than those who consumed 5. This was surprise to many, and was viewed by the media as a “setback to the hope that better diets can prevent breast cancer recurrence.”

Flawed Study Design
The most important nutritional factor in determining cancer development was not controlled for in this study: animal protein. Without controlling for the amount of animal protein, it is not surprising that no benefit was seen by merely increasing veggie and fruit intake.

Animal Protein Promotes Cancer Development
Dietary animal protein has been shown in animal studies to have dramatic effects on cancer development. Animals feed aflatoxin, a potent cancerous compound produced by mold growing on improperly stored corn and peanuts, will develop liver cancer if fed a diet high in casein, the predominant protein found in milk. All animals administered aflatoxin and fed a diet containing 20% casein developed liver cancer and were dead, or near dead, at 100 weeks. All animals given the same amount of aflatoxin, but fed a diet containing only 5% casein were alive and active at 100 weeks. Just decreasing the amount of dietary animal protein prevented expression and development of liver cancer.

When studies were repeated with diets containing high plant protein sources (20% soy and wheat) there was no cancer development. As if a switch was turned on, cancer growth was dependent on the amount of animal protein in the diet, a finding not seen with plant protein. If you want to read more on this, I suggest you read the China Study by Colin Campbell.

Breast Cancer and Animal Protein
Breast Cancer has been linked with an increased consumption of red meat and high fat dairy products during pre-menopausal years. We also know from population studies that American women have breast cancer rates 400% higher than the Japanese. However, Japanese women who move to the United States soon develop the same elevated risk for breast cancer as Americans, suggesting that there are dietary factors at work here. A likely culprit is animal protein; Japanese women consume more animal protein in their diets once they move to the United States.

Bottom Line
There are strong dietary links between cancer development and animal protein. Without controlling and significantly decreasing the amount of meat and dairy in this study, no improvement in breast cancer recurrence rates would be expected by merely increasing fruit and veggie intake. Only if the women were placed on a strict vegan style diet, which would include higher fruits and veggies but also eliminate meats and dairy, would I expect to see a protective effect against breast cancer recurrence.

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