In no uncertain terms did the American Heart Association (AHA)1 condemn a recent study by Mente et al2 in The Lancet: “The findings in this study are not valid” … “a flawed study” … “you shouldn’t use it to inform yourself about how you’re going to eat” read some of the statements in the AHA’s comment. The study in question suggested that not only will salt restriction not benefit most people, but it may actually be harmful if salt intake becomes too low. In only about 11% of the more than 100,000 study population, in patients who had high blood pressure, did salt restriction help to lower the risk of heart disease, stroke, or death.
This is the same AHA that for years has accepted fees to uncritically endorse as “heart healthy” scores of products by the Campbell Soup Company (Camden, NJ), products that contain far more salt than the AHA itself recommends for a heart-healthy diet. Specifically, the AHA recommended that consumers shouldn’t eat more than 1500 mg of sodium per day, and also preferentially choose low-sodium foods defined as having <140 mg of sodium per serving.3 Campbell’s AHA-certified products contained around 400 mg per serving, or between 600 and 1000 mg per unit, far from the AHA’s suggestions. If you plan to adhere to the AHA’S 1500-mg daily limit for sodium recommended, consider that a single serving of Campbell’s regular tomato soup (Figure) is almost one-third of that. Currently, the average American consumes about 3500 mg of sodium daily, an amount that has not changed over the past decades despite the drastic reduction in heart disease in the US.4 As documented by Andy Warhol’s canvas from the year 1961, Campbell’s canned soups with and without the “heart healthy” blessing of AHA have succeeded in maintaining a high dietary sodium intake in many Americans for more than half a century.
The study by Mente et al,2 like most studies, is not perfect and can be criticized. The authors themselves are critical, and so is an accompanying editorial by Eoin O’Brien.4 The AHA’s thoughts about salt restriction are based on multiple well-established observations that salt raises blood pressure and that in turn, high blood pressure is known to cause cardiovascular disease. However, it does not necessarily follow that lowering blood pressure by eating less salt will consistently decrease the risk of heart disease, regardless of whether you are hypertensive or have normal blood pressure, whether your salt consumption is excessive, moderate, or even low. According to Mente et al2 and many other studies, it seems very likely that a reduction of dietary sodium is beneficial in high salt eaters who also have high blood pressure. However, in people with normal blood pressure, lowering salt intake has little if any effect and may even be harmful when becoming too severe.5, 6 Similar to the editorial of Mente et al,7 we question the recent findings of a direct linear relationship between usual sodium intake and total mortality, with no evidence of a U or J shape curve at low levels of sodium intake.8 These findings do not provide iron-clad evidence of the safety or efficacy of low sodium intake (<2.3 g/day) because the mortality was not significantly lower between low and moderate sodium intake categories. A low sodium intake has been documented to stimulate the sympathetic nervous system and the renin-angiotensin-aldosterone cascade, both of which may be associated with increased cardiovascular disease events and mortality.9 Clearly, with sodium restriction, as is true more often than not in medicine, one size does not fit all.
Understandably, the AHA, despite its hypocritical endorsing policy, is unwilling to acknowledge that universal salt restriction may be controversial, that indeed the relationship between salt intake and heart disease may be far more complex than we originally thought. Perhaps, then, the AHA should take to heart the dictum of H. L. Mencken: “For every complex problem there is an answer that is clear, simple, and wrong.”
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-Franz H. Messerli, MD, Stefano F. Rimoldi, MD, Sripal Bangalore, MD, MHA
This article originally appeared in the April 2017 issue of The American Journal of Medicine.
