Apr 26, 2014 5:22 PM GMT
Interesting discussion on the radically changing science around nutrition and conventional health axioms we've been told over the years:
The hypothesis that fatty foods are a direct cause of cancer has also been crumbling, along with the case for eating more fiber. The idea that red meat causes colon cancer is shrouded in ambiguity. Two meta-analyses published in 2011 reached conflicting conclusions — one finding a small effect and the other no clear link at all.
If hamburgers are carcinogenic, the effect appears to be mild. One study suggests that a 50-year-old man eating a hefty amount of red meat — about a third of a pound a day — raises his chance of getting colorectal cancer to 1.71 percent during the next decade, from 1.28 percent. Spread over a population of millions, that would have an impact. From the point of view of an individual, it barely seems to matter.
Trying to tweeze feeble effects from a tangle of variables, many of them unknown, inevitably leads to a tug of war of contradictory reports. (As the San Diego meeting was winding up, a new paper on high-fat diets and breast cancer suggested there might be a connection after all.)
With even the most rigorous studies, it is hard to adjust for what epidemiologists call confounding factors: Assiduous eaters of fruits and vegetables probably weigh less, exercise more often and are vigilant about their health in other ways. Some of this can be sorted out with randomized controlled trials, with two large groups of people arbitrarily assigned different diets. But such studies are expensive, and the rules are hard to enforce in the short term — and probably impossible over the many years it can take for cancer to develop.