A new study was released showing that poorer people in Britain consume more salt than the rich. I don't doubt this is true. But, I seriously question the inferences drawn by the researchers and other commentators.
The authors of the study indicate that:
These results are important as they explain in part why people of low socio-economic background are more likely to develop high blood pressure (hypertension) and to suffer disproportionately from strokes, heart attacks and renal failure.
Really? Isn't poverty correlated with a bunch of other bad things that can result in adverse health outcomes? There is strong evidence that the poor smoke more, drink more, eat fewer veggies, weight more, and on an on. Yet, we are to believe that the culprit for all their problems is salt? Aren't there underlying factors, such as the evidence that the poor have lower discount rates (i.e., they value the future less), that are driving all these behaviors? In short: correlation with salt intake and poverty doesn't prove anything is causative. Yet, we'd need to know causation before public policies are recommended. Nevertheless, the researchers say that:
widespread and continued food reformulation is necessary through both voluntary as well as regulatory means to make sure that salt reduction is achieved across all socio-economic groups.
But, where is the evidence that such regulations or voluntarily actions would have the intended effect? There is actually quite a lot of debate (see here or here) about the health impacts of reducing salt in our diet.
And what would be the costs of such voluntary or forced actions? It might do good to ask why the poor eat more salt in the first place? One answer is alluded to in the press release: the poor are much more likely to work in jobs that require manual labor. You know - jobs that make you sweat. More sweating requires more salt intake. Another answer, also alluded to in the press release, is that the poor might eat more processed food which often contains more sodium. What the release fails to discuss is that, given job and family demands, the value of convenient, processed food might be relatively higher among the poor. Restricting access to such foods might very well reduce salt intake but it is unlikely to make their life measurably better. It is easy for a relatively rich researcher with a relatively flexible job to say that the poor would be better off if they cooked more fresh foods and stayed away from convenient, packaged foods. I suspect a single mother working two jobs would have a different opinion.