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Is Red Meat Safe?
Hoffman Center Staff
According to a new study, eating red meat can increase your risk of colon cancer. Should we immediately switch to chicken, fish, or dare I say it. . . tofu? On the other hand, is the National Cancer Institute not spending its money as wisely as it should?
Researchers from the National Cancer Institute and the American Cancer Society concluded in the Journal of the American Medical Association that "prolonged high consumption of red and processed meat may increase the risk of cancer in the distal portion of the large intestine."
This conclusion was based on a study of 148,610 adults aged 50 to 74 years who provided information on meat consumption in 1982 and again in 1992 and 1993 as part of their enrollment in the Cancer Prevention Study II. Through August 31, 2001, 1,667 cases of colorectal cancers were reported out of the 148,610 study subjects.
The first problem with the study began at the data gathering phase. The individuals that were collecting the food frequency information were not trained nutritionists or dietitians. They were merely untrained members of the lay public getting paid hourly. The data for the study was initially collected by 77,000 untrained volunteers who interviewed family and friends about their lifestyle habits. None of this lifestyle data was verified or validated. This is not how peer-review research should start.
The second problem with the study was that an examination of the data revealed no association between red meat consumption and overall colon cancer risk after considering the study subjects' exposures to other colon cancer risk factors. In other words, if you were overweight, did not exercise, smoked, or ate a lot of non-meat junk food and shunned healthy fish, fiber, fruits and vegetables, this was not taken into account.
To quote the researchers, "high intake of red meat reported in 1992 and 1993 was associated with higher risk of colon cancer after adjusting for age and energy intake but not after further adjustment for body mass index, cigarette smoking and other covariates."
After such a big budget study, there is intense pressure to find some statistical correlation or face the risk of possibly not receiving another grant for further research (the deathblow for many scientists). Could it be possible that the researchers then engaged in some "adjustments" of their data in hopes of discovering some statistical correlation they could point to as a risk?
Since there was no correlation between red meat consumption and overall cancer risk, the researchers examined their data looking to see whether there was an association between red meat consumption and cancer of the proximal colon, distal colon and of the rectosigmoid and rectum. The more analyses performed, after all, the greater the likelihood that some newsworthy result will be found, albeit the result of chance.
These subsequent analyses produced three correlations that resulted in attention-getting headlines. A 50 percent increase in distal cancer risk among high consumers of processed meats; a 53 percent increase in distal cancer risk among those with those with the highest ratio of meat to chicken and fish consumption; and a 71 percent increase in rectal cancer risk among high consumers of red meat.
With respect to the claims concerning distal cancer risk, both results are of unimpressive size. The fact is risks smaller than 100 percent donýt have much credibility and they are of borderline statistical significance. There is a strong possibility that the results are due to chance. What is the statistical weakness? Well, the statistical weakness is that the analysis involves only 79 and 92 cases of distal cancer, respectively. For these analyses to be statistically significant, they should involve hundreds, not dozens, of cancer cases.
Let's focus on the "71 percent increase in rectal cancer" claim. This conclusion was based on an analysis involving only the 1992 and 1993 data. When the analysis includes the 1982 data, the result drops to 43 percent and becomes statistically insignificant. That doesn't make sense if you think about it. How can you drop part of the study data? If the researchers didn't drop the 1982 data they would have an insignificant result. An insignificant report will not make headlines.
Now let's go back to my first point. Due to the untrained individuals gathering the data, exactly what and how much the study subjects ate, smoked, drank, and how much they exercised is really anybody's guess. If the data gathering process is weak, then the conclusion based on said data gathering is weak.
What about genetics? The genetic predisposition to colon cancer is thought to be a major risk factor. However, the researchers acknowledged in study that they didn't even have any information on family history of colon cancer for the analysis of 1992 and 1993 data, yet still made sensationalistic claims.
The results of previous studies on meat consumption and colon cancer have produced similar inconsistent, contradictory, weak and poor conclusions. There really is no persuasive evidence that meat consumption per se is in any way related to colon cancer risk.
Regardless of all these holes in the study, I couldn't help but wonder why nobody researches the "types" of meat in these studies. Grassfed, organic beef is a very clean, healthy source of protein, essential vitamins and minerals, and has a healthy fat ratio. Yet, it is guilty by association in studies that lump it together with preservative laden ribs, fried burgers, frankfurters and cold cuts.
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