One of the first principles taught to scientists is the dictum, “Correlation doesn’t imply causation.” That means that when two factors vary with each other, it doesn’t necessarily mean that one causes the other. For example, a study showing that men retiring from military service were healthier than other men their age doesn’t mean that being in the military is healthy – in fact, it may just mean that if you get seriously sick, you leave the military, leaving nothing but the more-healthy-than-average around when retirement hits.
Similarly, a study showing an apparent link between alcohol consumption and colon cancer was criticized by scientists at the Boston University Medical Center. While the study did show that more alcohol meant a higher colorectal cancer rate, BU scientists point out there were flaws in the method.
With 2.5 drinks or more a day, colon cancer rates go up. This applies whether or not there is a family history of the disease. But as the critique points out, there was no separation of the binge drinking crowd from the steady drinkers, and taking folic acid lowered risk in both populations. In other words, it may be a lack of folic acid that is causing the problem instead of alcohol directly. It should be noted that deficiencies in folic acid (and other water soluble vitamins) is a consequence of heavy drinking.
Another problem for the study, touted by addiction specialists as “proof” of another danger of drinking, was the age of the data used. Since the way colon cancer is diagnosed has changed, and gotten much better, old diagnoses only caught severe, more advanced cases. The real message of this study, according to critics, is that a family history of colon cancer, with or without alcohol, is a good predictor for the disease. Further, that taking folic acid if you are in this risk group (or eating dark green, leafy vegetables) is a good idea – maybe even a life saving idea.
