In an informative op-ed piece in the New York Times, Michael Alderman, an epidemiologist, questions a government campaign to reduce salt in processed food. His piece raises two (wildly different) questions.
1. Several studies have correlated less salt with worse health. Why? Alderman writes:
Nine [observational] studies, looking at a total of more than 100,000 participants who consume as much sodium as New Yorkers do, have had mixed results. In four of them, reduced dietary salt was associated with an increased incidence of death and disability from heart attacks and strokes. In one that focused on obese people, more salt was associated with increased cardiovascular mortality. And in the remaining four, no association between salt and health was seen.
And in the one experimental study that Alderman knows of, “the group that adhered to a lower sodium diet actually suffered significantly more cardiovascular deaths and hospitalizations than did the one assigned to the higher sodium diet.”
Those are useful facts. Alderman gives a few possible explanations. Here’s another one: Several popular fermented foods, including sauerkraut, buttermilk, miso, and cheese, are high in salt, and fermented foods protect against heart disease. I haven’t read the experimental study Alderman describes but it is unlikely that the two groups in that study ate food that was the same in every way except for salt content. What probably happened is that one group was instructed to choose a low-salt diet and the other group wasn’t. The low-salt group ate less salt in part by avoiding high-salt fermented foods (such as cheese).
2. Alderman writes:
[Observational] research can justify action only when multiple studies produce consistent, robust findings across a wide range of circumstances, as the research on tobacco and lung and cardiovascular health has done.
The puzzle is why he writes like this, which I find irritating. Most of the editorial is good, which makes this lapse especially interesting. I call this black-and-white speak, talking as if something complex was black and white and — always associated with this — people on one side are better than people on the other side. In my professional life, I hear black-and-white speak from some statisticians, who divide analyses into “correct” and “incorrect.” According to them you should analyze your data by following a set of black-and-white rules. Here is a less-irritating version of Alderman’s statement:
Successful public health campaigns have been built on observational studies but in the best-known case — the danger of smoking — the findings were consistent and robust across a wide range of circumstances.
See: no need to moralize. Alderman’s statement, of course, is just one example of something very common.
Ben Casnocha on another example of moralizing in the Times.
Doesn’t salt have anti-biotic properties–meat used to be preserved by being salted rather than frozen. Does the intersection of salt and fermentation do anything special, I wonder? Salt and fermentation seem at cross purposes to an extent. Does the salt kill or weaken bad bacteria from fermentation and allow your immune system to sample it, producing a process like vaccination which uses destroyed viruses?
I suppose that brine-adapted bacteria tend not to be human pathogens, because humans aren’t especially briny.
Andrew, maybe it’s a certain kind of moralizing I don’t like. I agree with you that it is actually a good thing to say this is good and that is bad, as you often do in your blog. But saying it in a way that implies that anyone who disagrees with you is a bad person or stupid or something like that — that I don’t like and think is unhelpful. The black and white aspect comes into it with false certainty: The statement is too strong as if the issue is really clear when it isn’t. As if there is less room for disagreement than there actually is.
For example, to say a certain graph is bad for reasons X, Y, and Z — that’s fine. That’s really helpful. But to say a certain graph is wrong — as you have never done, as far as I know — isn’t helpful at all. It implies that there are black-and-white rules about making graphs. That’s an unhelpful implication because making graphs is too complicated for that. Statements like that discourage thinking and encourage blind obedience.
Seth, I like the respect that you show for the point of view of others. In my own drive to keep growing, to keep learning, I’ve learned that a closed mind is great at action, but not at listening. An open mind leaves a chance for someone to drop a worthwhile idea in it.