Non-Trivial Pursuits: Playing the Research Game
Liebman, Bonnie, Nutrition Action Healthletter
Welcome to the world of science, Ms. Howard. We're not surprised that you're confused. It's not a comforting, here's-how-the-world-works place, like the textbooks portrayed it in junior high.
But you'll feel less like a ping-pong ball once you see how many--and what kind of--studies researchers have to complete before they can state with reasonable certainty that a food or supplement causes or prevents a disease.
Most of those "well-publicized studies" you hear about are just one step in a game we call "Non-Trivial Pursuits."
"New Study Finds Vitamins Are Not Cancer Preventers," ran the headline in the New York Times last July.
It was the second time in three months that the "antioxidant" vitamins had failed to prevent cancer.
In April, a study of 29,000 Finnish smokers found an increased incidence of lung cancer in men taking beta-carotene (vitamin E had no clear effect). And in July, betacarotene, E, and C failed to prevent precancerous colon polyps in 864 Americans who had already had a polyp removed.(1)
Are these results disappointing? Yes. Are they proof that antioxidants don't work? No. But to some people, the failures meant that scientists were stupid, out to discredit vitamins, or both.
"True, the finding of harm from betacarotene is puzzling, and may well be refuted by future trials," wrote New York Times science editor Nicholas Wade in an op-ed piece last May. "But that cannot be presumed."
How can Wade be so unfazed when people are tearing their hair out trying to get some straight answers? Perhaps because he understands how research works.
"What medical journals publish is not received wisdom but rather working papers...," write New England Journal of Medicine editors Jerome Kassirer and Marcia Angell. "Each study becomes a piece of a puzzle....No matter how important the conclusions, they should usually be considered tentative until a body of evidence accumulates pointing in the same direction."
PROVING CAUSE AND EFFECT
"Ignoring dozens of positive studies published in the last decade, the media has given enormous coverage to a single badly flawed Finnish study which supposedly showed negative results," charged Citizens for Health, a lobbying group supported by the supplement industry, last April.
But unlike the Finnish study, virtually none of those dozens of "positive" studies were randomized, double-blind, placebocontrolled clinical intervention trials, which actually give people antioxidants (or whatever) and then wait to see what happens. Trials are less likely to suffer from pitfalls (see page 8).
For example, most of those "positive" studies simply "observed" lower cancer rates in people who consumed antioxidant vitamins, usually from a diet rich in fruits and vegetables. …