Colon Cancer, Its Link To Diabetes, And Dietary Pattern

Study the etiology of cancer and one thing becomes evident - it's not the result of one or even a few conditions.

That's true about many chronic diseases. Hallmarks of diabetes for example - insulin resistance, high fasting and post-meal blood glucose, high or low blood insulin, fatty acid pathology - emerge from a confluence of factors, both genetic and environmental. ("Environmental" includes how someone eats.)

Cancer and diabetes aren't caused by eating one particular food either. While eating carbohydrates can result in high blood glucose in people with diabetes, eating carbohydrates by no means causes diabetes. (Some types of carbohydrates are more prone to raising blood glucose (BG) than others, some have no effect on BG at all, some actually lower BG.)

Similarly, a diet high in meat does not cause colon cancer, although it appears to contribute to the disease in predisposed individuals. But then, carbohydrates, at least certain ones, appear to contribute to cancer too. Likewise diets high in meat and fat have been shown to contribute to diabetes.1

When it comes to food, it's likely the pattern of eating, rather than the contribution of a single nutrient, that plays the larger role in cancer and diabetes risk.
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I thought the Discussion section in this study laid out the link between cancer and diabetes nicely (and drew attention to a risk-laden style of eating along the way):
Dietary Risk Factors for Colon Cancer in a Low-risk Population, American Journal of Epidemiology, 1998

First I'll summarize its results.

It was a 6-year prospective study of over 32,000 Seventh-day Adventists living in California, a unique group that enjoy very little alcohol, tobacco, and meat. They also enjoy a low incidence of colon cancer. Were their vegetarian diets protective? Possibly. After adjustment for alcohol, smoking, and a few other things, here's how their diets affected their risk:

"The authors found a positive association with total meat intake (risk ratio (RR) for ≥ 1 time/week vs. no meat intake = 1.85)."

So, there was a 1.85 greater probability of colon cancer for those who consumed meat once a week or more compared to not at all. That's an 85% increased risk. Pretty high.

"Among meat eaters ... positive associations with red meat intake (RR for ≥ 1 time/week vs. no red meat intake = 1.90)."

A 90% increased risk for red meat alone. Even higher.

"... and white meat intake (RR for ≥ 1 time/week vs. no red meat intake = 3.29)."

And here, an incredible 329% increased risk for eating white meat at least once a week. You just don't see RRs that high. I was surprised that white meat was associated with a higher risk than red meat. The iron in red meat, its ability to oxidize, is thought to contribute to colon abnormalities. Something stronger must be working here. In this case, white meat included poultry and fish.