Depending on your taste preferences for food, and food for thought alike, you either welcomed the recent Institute of Medicine report on salt indicating the lack of evidence for intake levels below 2,300 milligrams per day, or winced. I have a fairly centrist palate in both contexts and wound up taking the report with, well, a grain of salt. We'll get back to my palate, and why the one thing I can't stomach is nutritional ping-pong, before the end. First, let's consider the report itself.
A special committee of the Institute of Medicine was convened at the request of the Centers for Disease Control and Prevention to examine the recent evidence relating sodium intake to health outcomes. The IOM committee did not conduct any new research. Its charge was to review the prior literature, with particular attention to the following: methodological rigor of available studies; relevance of the data to the population at large and particular high-risk groups such as those with diabetes or congestive heart failure. The committee also looked at the links between variation in sodium intake and variation in decisive health events, such as heart attack or stroke, rather than risk factors like high blood pressure.
The committee's provocative conclusion was that evidence to support a clear health benefit for the population at large from reducing sodium intake below 2,300 milligrams a day is lacking. It further suggested that available evidence, while limited in quality, quantity and consistency, hinted at potential harms for the high-risk groups when reducing daily sodium intake to 1,500 milligrams or below. The committee thus suggested that a target of 2,300 milligrams is, for now at least, appropriate for everyone – and that lower could potentially be ill-advised.
That, in a lightly salted nutshell, is the content of the report. Media coverage of it, predictably, ranged from moderate to the more overtly sensationalist, the latter variety emphasizing potential dangers from the overly restrictive recommendations that now prevail.
All of this was seemingly welcome news to those who like salty food, enjoy the idea that so-called experts in nutrition never actually know what they are talking about or cheer on the iconoclasts from Atkins to Taubes.
On the other hand, the sudden redirection was apt to be rather distasteful to fans of the Center for Science in the Public Interest, those who agree with the concerns expressed by the American Heart Association that the new report does not adequately consider the association between sodium and blood pressure or anyone aware of and persuaded by a recent study published in the journal Hypertension indicating that population-wide sodium reduction in the United States could save as many as 500,000 lives over the next decade.
A meta-analysis published just last month in the Cochrane Database of Systematic Reviews also opposes the new report. The meta-analysis, based on studies of more than 3,000 people, indicated that while some sodium reduction is good, more is in fact better for blood pressure reduction and the attendant cardiovascular benefits.
If some are indeed inclined to savor the new report, while others are prone to choke on it, the question is: Can we reconcile such diverse appetites to our current understanding? If we cared at all for doing so, the answer is clearly yes.
What will be missing for all who only read headlines, which is apparently an ominously high percentage of us – although clearly not you if you are still with me! – is that virtually all experts concur we eat too much sodium, and it's hurting us. As noted in the new IOM report, average U.S. adult daily intake of sodium is 3,400 milligrams. That's not just a bit over the 2,300-miligram threshold the IOM report is reaffirming; it's more than a gram over it. On average, even if we toss out the lower intake recommendation of 1,500 milligrams entirely, we still get more than 1000 milligrams too many. That's not even close.
The more conspiracy minded among us might be inclined to indict proponents of salt restriction for all the harms imposed by advocating for too low an intake level. But there is no there, there – because while lower intake has been espoused, it has virtually never been achieved outside of randomized trials. In fact, prominent researchers have long suggested that achieving recommended sodium intake levels in the absence of a fairly massive food supply overhaul is all but impossible.
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So what this all comes down to is that we still have cause to reduce our sodium intake a lot, just not a lot more than a lot, to derive a substantial, if not dramatic, public health benefit. We consume way too much sodium, and if we ever manage to start fixing that – we should be careful not to overshoot.
That doesn't quite have the conspiracy theory sex appeal of "experts wrong again!" But that, really, is what the new report means. And there is the further proviso that we weren't reducing our sodium intake very effectively in the first place. Maybe we could get going before we worry too much about going too far?
Which leads to the one real worry I have about all of this. While science should continuously challenge itself, media hype and public perception of the revisions that result when it does so threaten to conjoin baby and bath water. There may in fact be beneficiaries of such perpetual doubt – but the public health does not tend to be one of them.
We can learn new things, including the limits to what we thought we knew, without abandoning all prior knowledge. As I've had cause to note before, we play ping-pong with scientific evidence at our peril.
We eat too much sodium and most of us stand to benefit from eating less, which would tend to occur by the way as a fringe benefit of eating more wholesome, less processed foods – since some 80 percent of our salt is processed into our food, not shaken onto it.
Perhaps we could, in theory, go too far and wind up eating too little salt. But our population has a long way to go before that is more than a theoretical concern. In the interim, efforts to reduce sodium intake should persist if we have any hope of getting to the sweet spot.
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David L. Katz, MD, MPH, FACPM, FACP, is a specialist in internal medicine and preventive medicine, with particular expertise in nutrition, weight management, and chronic-disease prevention. He is the founding director of Yale University's Prevention Research Center, and principal inventor of the NuVal nutrition guidance system. Katz was named editor-in-chief of Childhood Obesity in 2011, and is president-elect of the American College of Lifestyle Medicine.