Dietary guidelines often change, but “restrict your salt intake” has resisted the advances of science. The National Academy of Medicine recently reiterated its advice to limit daily sodium intake to 2,300 milligrams (a little over a teaspoon of salt), or 1,500 milligrams for those at risk of cardiovascular disease. An article last week in the New England Journal of Medicine endorsed that view and called for the Food and Drug Administration to impose voluntary sodium limits on 150 food categories.
These recommendations ignore scientific developments and may be harmful to your health. In March we published an article in the Lancet summarizing six decades of research on sodium intake in more than a million people world-wide. We found the sodium “sweet spot”—the intake range associated with the lowest risk of disease and the longest life expectancy—to be between 3,000 and 5,000 milligrams a day, considerably higher than the usual recommendations. Once daily sodium consumption falls below 3,200 milligrams, all-cause mortality increases and life expectancy decreases dramatically.
Adequate sodium is crucial for biological processes including nerve conduction, muscle contraction, and sustaining the fluid balance necessary to assure blood flow and deliver nutrients and oxygen to every cell in the body. As recently reviewed in the New England Journal of Medicine, human physiology has evolved a complex process, mediated by the brain, to maintain sodium balance precisely. If we consume too little sodium, our kidneys will go to extremes to conserve it. If we consume too much, it is eliminated through our skin, intestines, and kidneys. You’re far likelier to die from failure to maintain this precise control than from the modest impact salt may have on your blood pressure.
People listen to their bodies. Despite vigorous efforts by government and advocacy groups, average U.S. sodium intake has remained constant at 3,600 to 3,700 milligrams a day. In 2005 the British government undertook a determined effort to reduce sodium content in processed food, as the FDA is now being urged to do. Britons adjusted their eating habits. In 2014 the government reported that the reductions in sodium content had led to no significant change in sodium intake.
Understanding the stark contrast between the National Academy of Medicine’s recommendation and what science has identified as sodium’s healthy range is critical to the nation’s health. Minimal decreases in serum sodium predict increased mortality in healthy people. Although this is not fully understood, we know that risk increases when sodium intake breeches the lower limits of the brain’s ability to maintain serum sodium within its narrow range—especially in healthy middle-aged men, for whom it nearly doubles the risks. Comparable increases in risk exist for the ill and the elderly. Low serum sodium at hospital admission is associated with increased length of stay, in-hospital death, and discharge to a care facility. If, contrary to the British experience, the prospective FDA restrictions on sodium in food prove successful in reducing intake, that could magnify the risk for Americans.
The U.S. Department of Agriculture and the Health and Human Services Department are currently deliberating their quinquennial federal dietary guidelines, with release slated for next year. The government should address and incorporate all available evidence into its dietary guidance. Fortunately, no government policy can override our craving for salt.
Dr. Alderman is an emeritus professor at the Albert Einstein College of Medicine. Dr. McCarron is a physician in private practice in Portland, Ore.