The Institute of Medicine issued a report this week evaluating the evidence on links between salt intake and health (press release here;NYT report here). The key: instead of looking at proxy indicators of health (like blood pressure), they focused on actual health outcomes (like dying). The conclusions: (a) evidence on the effects of low-salt diets is patchy at best; and (b) with the evidence that exists, there’s little support for advocating sodium intake below 2,300 mg/day, and some evidence that such low levels may actually be harmful. The average intake among Americans is 3,400 mg/day, equivalent to 1.5 teaspoons of table salt.
I’ve written about the sketchy evidence on salt several times, but this is the first time I’ve seen the evidence seriously considered by such a powerful body with the potential of influencing actual policy and dietary recommendations. It’s a good sign that these organizations are responding to changing evidence (though the American Heart Association and the Center for Science in the Public Interest have announced that they firmly disagree with the new report).
A couple of points that I’ve made in previous blog entries:
Salt intake hasn’t been increasing in recent years. Despite all the talk of an “epidemic” of salt caused by the high levels in processed foods and restaurant meals, a study back in 2010 looked at historical trends in salt consumption, using only salt levels measured through excreted urine. As expected, they found an average intake of around 3,700 mg/day — and more surprisingly, they found that level was fairly constant throughout the 50 years spanned by the studies. Moreover, another review found similar results looking at studies from 33 other countries. If salt intake has been relatively constant for half a century, it’s hard to blame the more recent rise in hypertension on it.