Monday, July 5, 2010

Medical Controversy: When is a Controversy Over?

Quick... what change of diet is the best way to reduce your blood pressure? What has been shown to cause headaches and other problems and should be removed from processed foods? What common seasoning is bad for you?

Did all your answers involve salt? Simple ordinary table salt? It's common knowledge that salt isn't good for us. Since it's common knowledge it must be true right?


What if the science isn't so clear cut? What happens when the vast research includes studies and calculations that support both sides? What happens when researchers want to find out more about the risks and the benefits while anxious public health officials want to make decisions right now?

In 1999 Gary Taubes won a Science in Society Journalism Award from the National Association of Science Writers for his article The (Political) Science of Salt.

Maybe the link between salt and hypertension isn't as strong as we think. Maybe, as the article states over a decade ago, as research continues the benefits of salt reduction are seen to be smaller and smaller. This is a good example of how complicated issues are and how difficult it is to even agree which studies are good and useful and which aren't. To quote the article:
One-sided interpretations of the data have always been endemic to the controversy. As early as 1979, for instance, Olaf Simpson, a clinician at New Zealand’s University of Otago Medical School, described it as "a situation where the most slender piece of evidence in favor of [a salt-blood pressure link] is welcomed as further proof of the link, while failure to find such evidence is explained away by one means or another." University of Glasgow clinician Graham Watt calls it the "Bing Crosby approach to epidemiological reasoning" — in other words, "accentuate the positive, eliminate the negative." Bing Crosby epidemiology allows researchers to find the effect they’re looking for in a swamp of contradictory data but does little to establish whether it is real.
Even if the studies and the data have become clearer in the last decade there are important underlying questions brought to light in the article.
  • What happens when one piece of the puzzle (let's say salt) is only part of a much more complicated mechanism (for instance how the body maintains blood pressure)? Maybe it isn't always possible to reach simple conclusions in all cases.
  • Who gets to decide which studies are good and which are bad? The concept "it doesn't support my view so it must be wrong" works to explain every point of view.
  • When should incomplete or unfinished science be used to form public policy? Should public health officials change official policy after each new discovery or wait for long term results? What happens when science gets applied to whole populations of people?
  • Who can act as arbiter and interpreter in the middle of scientific controversies? Who can explain what is going on to the rest of us? I don't want to hear from someone who's attached to one side of each controversy.
  • If enough people think that reducing salt reduces blood pressure then is the controversy over before the science has been made clear? Could we end up with a massive public re-education campaign explaining that salt reduction isn't necessarily good in some cases?
I could go on. It's a fascinating read and well worth your time. Gary Taubes' article gives some insight into the human nature of science. All while still leaving me unsure whether I'm allowed to add salt to my food.

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