Numerous publications attest to the observation that a high salt intake can trigger hypertensive cardiovascular disease de novo or accelerate pre-existing hypertension. For decades practicing physicians have warned their patients about excessive salt intake. The World Health Organization (WHO), the American Heart Association, the European Society of Cardiology and the Centers for Disease Control and Prevention (CDC) have all published guidelines to reduce habitual salt intake not only for patients with hypertension but also for normotensive subjects, commonly below 2 grams of sodium (which corresponds to 5 grams of salt).

If indeed salt has to be considered a “cardiac nemesis” and must be held responsible for countless premature deaths, we can expect a high dietary salt intake to curtail life span. We tested this hypothesis by analyzing the relationship between salt intake and life expectancy as well as all-cause and cause specific mortality in 181 countries worldwide.

Among the 181 countries included in this analysis, we found a positive correlation between salt intake and healthy life expectancy at birth (β=2.57, R2=0.661, p<0.001), as well as healthy life expectancy at age 60. All-cause mortality correlated inversely with salt intake (β= –131, R2=0.597, p<0.001). In a sensitivity analysis restricted to 46 countries in the highest income class, salt intake continued to correlate positively with healthy life expectancy at birth (p<0.001) and inversely with all-cause mortality (p<0.001).

Figure Legend: Life expectancy and all-cause mortality related to sodium intake in 181 countries worldwide. Note that current arbitrary recommendations of salt intake by AHA, WHO and ESC are associated with rather low life expectancy and high mortality.

 

Salt the elixir of longevity? Our finding of salt intake correlating positively with life expectancy and inversely with all-cause mortality in 181 countries worldwide, argues against dietary sodium intake being a culprit of curtailing life span or being a risk factor for premature death. It also puts a question mark behind the recommendations of AHA, WHO, ESC and CDC.

However, our data are strictly observational and should not be used as a base for nutritional interventions. We therefore purposefully refrain from making any projections or dietary recommendations. These were inappropriately made time and again by salt reduction evangelists despite the lack of evidence regarding hard endpoints. Whether or not changing salt intake ultimately will affect life expectancy or all-cause mortality, individually or at country level remains unknown and cannot be inferred from the present data.

 

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3 Comments

  1. Nice paper, Franz. Really important to pay attention to this statement:

    “However, our data are strictly observational and should not be used as a base for nutritional interventions. We therefore purposefully refrain from making any projections or dietary recommendations. These were inappropriately made time and again by salt reduction evangelists despite the lack of evidence regarding hard endpoints.”

    The restraint is admirable. The point here is that the current AHA/WHO/ESC recommendations are all based on the link between sodium and BP, but we need to remember that these small changes in BP can’t be automatically translated into overall population health. So there’s no good basis for any firm scientifically based recommendation in any direction. Perhaps, as I’ve written before, experts should first acknowledge what they don’t know, so that it then becomes possible to study the question and find a question. If you were a funder of research why would you fund a project to answer a question that the experts already claimed to know the answer?

    Second, I would like Franz and others on this site to address the separate question of what specifically clinicians should tell their heart failure and hypertensive patients about sodium.

  2. Great paper! It is useful to question nutritional research with more nutritional research. But it does make me wonder if should we give up on the large-scale observational stuff entirely and focus on neat physiological studies? Like this https://pubmed.ncbi.nlm.nih.gov/15976364/ (Disclaimer: I worked with this group as a student many years ago) Perhaps the public would be more willing to buy into recommendations based on small scale mechanistic work?

    1. But Alex, it shouldn’t be about what the public is willing to buy! Science-based recommendations shouldn’t be based on mechanistic studies or on observational studies, or at least not for such a broad-based question with significant disagreement within the scientific community. (Tobacco is always the one good exception to this type of rule. But salt, of course, is not tobacco.)

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