High Protein Diets Raise Colon Cancer Risk? No.

In the more bad science department, MSN online published an article today with the title "High-protein diets may raise colon cancer risk."  It reports the results of a study done a team of researchers led by Dr. Harry J. Flint, of the University of Aberdeen and published in the American Journal of Clinical Nutrition.  Here's how the article describes the study:

"The findings are based on 17 obese men who each followed three short-term diets: a one-week menu plan designed to maintain their weight; a four-week high-protein diet with moderate amounts of carbohydrates; and a four-week high-protein diet low in carbs.

The first diet, which allowed about 360 grams of carbs per day, typically offered cereal, eggs and toast for breakfast; a sandwich and salad for lunch; and chicken, fish or soy, along with pasta, for dinner.

The low-carb diet — which allowed just 22 grams of carbs each day — generally consisted of eggs-and-bacon breakfasts, and lunches and dinners heavy in meat, poultry and fish, along with some vegetables and cheese.

The moderate-carbohydrate diet allowed 181 grams of carbs each day. Both high-protein diets contained just less than 140 grams of protein per day.

At the end of each diet period, Flint's team analyzed fecal samples from the men to look at levels of certain metabolic byproducts."

So do you notice anything funky about this description?

How about this:  they fed the men the high carbohydrate diets for only one week, but the lower carbohydrate diets for four weeks, before taking fecal samples.  This falls into the category of not minimizing variables. How does this kind of study get past peer review?

But of course if you want to create a "study" that favors the high carbohydrate diet, you might just fool around like that.

The really valuable paragraph in this report goes like this:

"The study looked only at short-term shifts in certain compounds that are byproducts of metabolism, and not actual disease risk. So it does not show whether high protein diets really raise the risk of any colon diseases."

Which outright contradicts the sensational title. 

If you want to know whether high protein diets increase colon cancer risk, how about studying Eskimos/Inuit?  Eating their native diet consisting almost exclusively of meat and fat, containing little or no fiber, they had no colon cancer.  How about the Masai?  Eating their native diet of meat and milk products, again, no colon cancer. These samples alone disprove the idea that meat causes and fiber prevents cancer as surely as finding one black swan disproves the statement "all swans are white."

Meanwhile, Dr. Oz, poster boy for the "healthy whole grain diet" rich in fiber that supposedly protects against cancer, turns up with colon polyps, possible precursors to colon cancer. 

As the MSN article says, "obesity is thought to be a risk factor for a number of diseases, including colon cancer."

As explained by Loren Cordain and Michael Eades in this article, both obesity and colon cancer arise from excess insulin production, which is driven by carbohydrate ingestion, not meat or protein intake. Colon cancer falls in the category of epithelial cell malignancies.  Cordain and Eades explain how diets high in refined carbohydrates promote hyperinsulinemia, which raises levels of insulin-like growth factors (IGF), reduces IGF binding proteins, and disables the body's natural antitumor system based on vitamin A activation.

Like other cancers, the prevalence of colon cancer has increased in tandem with increases in consumption of carbohydrates, including fiber, not increases in protein or meat consumption. 

Moreover, as I discussed in my article Fiber Fallacies, these researchers could do a little research and find that high fiber diets have been repeatedly shown to produce changes in colon tissue that precede cancer, or in some cases, actually increased the number of cancers relative to a fiber-free diet: 

Many people think eating a high fiber diet will prevent colon cancer; but we not only have no proof or even weak evidence that ingestion of fiber prevents colon cancer, on the contrary we have experimental evidence indicating that diets high in fermentable fibers actually increase colonic cell proliferation of the type that leads to cancer.

Lupton et al reported that a diet high in fermentable fiber increased cecum size and large intestine length, and reduced pH and stimulated cell proliferation, in rat colons. [J. Nutr. 118: 840-845, 1988.]

Jacobs and Lupton found that when they fed rats a high fiber diet based on either oat bran, pectin, or guar, the yield of proximal colonic adenocarcinomas increased by 4.5 to 5 times over the fiber free level. [Cancer Research 46, 1727-1734, April 1986]

Mandir, Englyst, and Goodlad found that when they fed mice fiber in the form of bran or apple pomace, both fibers significantly increased cell proliferation, number of polyps, and tumor burden born by the mice. Both fibers increased polyp diameter, bran by 243% and apple fiber by 150%. [British Journal of Nutrition (2008), 100, 711–721].

Generally, diets high in fiber make the feces softer and looser. A study by Inoue et al found “Soft or loose feces increased the risk for all subsites of colorectal cancer, particularly in female rectum cancer (odds ratio [OR] = 4.5)” [Cancer Causes Control 1995 Jan;6(1):14-22.]. Although epidemiological studies generally don’t carry much weight, when the odds ratio goes above 2.0, the association carries more weight. This finding of a greater than 4 fold increased risk of colorectal cancer in people with soft or loose stools suggests that high intake of fermentable fiber may promote cancer in humans as well as rats. 

Kok-Yang Tan and Francis Seow-Choen dispensed with all the myths of high fiber consumption in their article Fiber and colorectal diseases: Separating fact from fiction published online in the World Journal of Gastroenterology.   I suggest that these physicians take some time to read it instead of wasting their time beating a dead horse.  High protein diets don't cause colon cancer, and high fiber diets don't prevent it.  On the contrary, we have some pretty good reasons to believe that high fiber diets promote colon cancer.  Conventional 'wisdom' dies hard, but it will die.