Salt Assault and Failing to Match Policy to Data

So, stuck in traffic this morning, heard this offering on NPR about salt being evil evil bad bad, except in tiny, tasteless doses. But, wait, I thought: isn’t this whole salt thing a classic canard? SciAm seems to think so

Got work to do, so I’ll (cop out alert!) leave it as an exercise for the reader to track down some links, but I recall having looked into this about 15 years ago, when my blood pressure first got elevated enough for my doctor to notice. What I recall is that research showed *some* linkage between salt intake and blood pressure, but only for a minority of the population – something like 30%. For 70% of people, there doesn’t seem to be a link between salt intake and blood pressure at any realistic level of salt consumption.

But check out what happens: across populations, if any measurable minority is adversely affected by consumption of X, then the outcome for the entire group will be better if X is reduced for everyone  – *even if* reducing X has no effect on the vast majority of people. If people enjoy X, a policy to restrict X across the population is annoying and pointless for most people, but does achieve a better result *for the population* because it helps a few people, whose results roll up to the population as a whole.

The sane policy would be to seek a reliable way to tell if a given person falls into the group affected by X, and then having them reduce their consumption of X *only if* they belong to that group. Then unaffected people get to enjoy their X in peace, outcomes are better for those affected by X, and – outcomes for the whole population are better as well as each person’s individual outcomes are rolled up into a general measure.


But with salt, the policy has never been let’s find out *if* someone is sensitive to salt intake – instead, the medical field (as personified in my doctor) tell us all it would be a good idea to reduce our salt intake prior to knowing if, in fact, it will make any difference for that particular patient.

Now, this would be utterly trivial except for a couple things:

1. For most people,  changing their diets is hard, as in really, really hard. What we eat is among our oldest, most ingrained habits. So, what is being asked for here is not, subjectively, some trivial thing.

2. There’s this idea of personal capital – a doctor, and the medical establishment in general, have a somewhat limited amount of capital with each of us patients, and asking us to do stuff uses some of it. In such an environment, doctors should spend their capital carefully – if they make a big deal out of salt consumption, they may get less compliance on things of more  importance. As someone who ultimately has to sell stuff for a living, I keep this rule always before my eyes: you can only ask for so much of somebody’s time and energy, don’t waste it.

There are political implications from this line of thought as well, but gotta get back to work.

Author: Joseph Moore

Enough with the smarty-pants Dante quote. Just some opinionated blogger dude.

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