Despite evidence linking salt intake to hypertension and cardiovascular disease, salt intake in the US diet is actually on the rise. These worsening trends have led to calls for population-wide interventions to reduce salt in the US diet,27
as have already been adopted in other countries.7
Our findings provide evidence to support these calls. Our postulated 3 gm/day reduction in dietary – a reduction in the range targeted by other developed countries -is projected to benefit the entire US population and yield substantial reductions in morbidity, mortality, and costs. The population-wide benefits from salt reduction are similar in magnitude to the health benefits that would accrue from other public health and clinical interventions and would be cost-savings, even if only a more modest 1 gm/day reduction is gradually achieved over time. Changes in behavior are notoriously difficult to achieve, and individual approaches to achieving lower dietary salt have largely proven ineffective. Nevertheless, cholesterol levels fell in the US prior to the widespread use of medications, and smoking rates have fallen substantially through a combination of regulatory, public health, and individual approaches to smoking cessation. The large and growing burden of hypertension despite improved medical therapies28
and the potential for lower dietary salt to aid in the prevention and treatment of hypertension reinforce the urgent need for this approach.
Considerable literature links higher salt intake with higher blood pressure and increased cardiovascular risk,15, 29
and randomized trials have demonstrated that a lower salt diet lowers blood pressure16, 30
and cardiovascular risk.31
Despite concerns about the accurate assessment of salt intake, adherence with low-salt interventions, and theoretical increased risks of very low salt diets, several large meta-analyses and reports from the Institute of Medicine3, 5, 15, 26, 32
concluded that reducing dietary salt would lower blood pressure and cardiovascular risk. Professional societies including the American Medical Association, the American Heart Association, the American Society of Hypertension, and the World Health Organization have all endorsed population-wide efforts to reduce salt intake.
Our results are similar to other analyses33, 34
and extend them in important ways. We incorporated updated prevalence distributions of cardiovascular risk factors, particularly hypertension, in the entire US population and in black and non-black subpopulations. We considered current levels of hypertension treatment, treatment and control of other cardiovascular risk factors, and competing and ongoing risks among persons in whom deaths were averted. Our comparisons of the cardiovascular benefits of salt reduction were similar to those anticipated for established public-health targets such as tobacco, obesity, and LDL cholesterol. Targeted interventions have very large per-person effects, but their benefits are restricted to the smaller numbers of higher-risk, affected individuals. Lowering salt in the US diet would result in small but measurable blood pressure reductions across the entire US population, thereby reducing cardiovascular disease in all adults at risk.
A national regulatory effort to lower dietary salt intake would be cost saving even if only modest salt reduction were achieved after a decade-long period. If the population-wide approach to lowering salt were a federal effort, the healthcare savings to the current major federally sponsored healthcare program – Medicare- would be greater than the cost of the regulatory intervention itself, even without incremental benefits afforded to younger, non-Medicare-covered persons. Some costs, such as those borne by the food industry in reformulating processed foods, are not considered in these analyses. However, as salt intake is reduced, individuals appear to prefer food with less salt,15
likely related to accommodation of taste receptors - a process that occurs over weeks to months.35
In the UK a 10% population-reduction in salt was achieved over 4 years36
without reduction in sales of the products included in the initial voluntary effort and without consumer complaints about taste. The magnitude of the health benefit suggests that salt should be a regulatory target of the Food and Drug Administration, which currently designates salt as a food additive that is “generally regarded as safe.”27
We projected that certain sub-populations may experience a proportionately greater benefit from similar levels of salt reduction. Blacks have high rates of hypertension and cardiovascular diseases that contribute to racial disparities in mortality;37
their benefits from salt reduction could potentially narrow these disparities. Women would also experience a proportionately greater benefit because of their higher risk for stroke.11
Young and middle-aged adults could benefit because of the relative importance of blood pressure elevations in younger adults without major risk factors. Blood pressure elevations in young adulthood accelerate atherosclerosis9
and morbidity by middle age,38
yet younger adults with hypertension are less likely to be on treatment or have their blood pressure controlled.39
The benefits of salt reduction could be even greater than we projected because hypertension may be completely prevented or its onset delayed by lowering salt intake even earlier during childhood and adolescence.40
Projections such as ours are limited by uncertainty in the modeling inputs. We modeled the effects of salt reduction on blood pressure based on published data and assumed that the health benefits of salt reduction were mediated through these blood pressure reductions. We did not account fully for possible effects of salt reductions unrelated to blood pressure, such as potential improvements in outcomes of the increasing numbers of patients with heart failure or prevention of other highly morbid conditions such as end-stage renal disease. Our estimates of differential effects of salt reduction by age and race were extrapolated from clinical trial data, and there is more uncertainty about these effects on the total population; however, sensitivity analyses suggest that our primary findings are not very dependent on variations in these assumptions. We modeled only linear effects of salt reduction on reductions in blood pressure. Others have suggested that these effects may be non-linear,16
with greater reductions in blood pressure at lower salt intake; such an assumption would result in larger reductions in cardiovascular disease than we present here.
Even with these limitations, our simulations suggest that modest reductions in dietary salt would yield substantial health benefits across the adult US population by lowering cardiovascular event rates, deaths, and medical costs. Our findings support the urgent need for action to achieve these readily attainable benefits to the cardiovascular health of the nation.