How important is it for the average person to limit salt? Worldwide, more than one billion adults have hypertension, and, in 17%-30% of cases, the hypertension is related to excess dietary intake of salt.
Historically, salt has been a commodity, a preservative, and a flavor enhancer. The salt shaker has a special place in most kitchens or dining room tables.
Therefore, when dietitians or other health care provides suggest to patients that they should reduce or limit salt intake to lower blood pressure (BP) and prevent fluid retention, they are often very resistant. However, it is not just patient resistance that makes salt reduction difficult.
Salt, or sodium chloride, is used by food manufacturers in all types of food products. This means that much of the sodium patients consume comes from processed or restaurant food items. In fact, almost 77% of sodium intake is from processed foods in most developed countries (J Am Coll Nutr 1991;10:383-393).
Through these food items, Americans may consume double the recommended intake of sodium, potentially contributing to more than 7.6 million premature deaths and billions of dollars in health care costs (CMAJ 2009;181:605-609).
It has been well documented that salt-sensitive patients benefit from a reduction in sodium, but in patients who are not salt sensitive, one may question whether reductions in salt or sodium should be recommended for hypertension.
A 2011 meta-analysis found that reductions in salt intake result in decreased urinary sodium excretion and decreased systolic BP in normotensive individuals and those with hypertension or heart failure. This reduction in urinary sodium excretion and BP did not appear to translate into decreased cardiovascular or all-cause mortality (Am J Hypertens 2011;24:843-853). A limitation of this meta-analysis was the lack of end points; therefore, while large effects could be detected, small or moderate effects may not be found.
It is these small effects, which over a lifetime, may cumulatively impact quality of life, mortality, and health care costs for a nation. In fact, Frohlich and Susic (Circulation. 2011;124:1882-1885) suggest that more attention needs to be paid to the “subtle adverse end points of dietary salt excess.”
Within this review, the authors outline the organs impacted by excessive salt intake (heart, arteries, and kidneys) and highlight experimental studies conducted in animal models demonstrating that salt loading results in local pathophysiological changes. Years of continuous excessive salt consumption may lead to elevated BP and multi-organ structural and functional damage.
Due to this potential organ damage and subsequent impact on health care costs and mortality, communities and countries have begun instituting public policy regarding salt reductions. It has been estimated that a “population-wide decrease of 2 mm Hg diastolic blood pressure could lower the prevalence of hypertension by 17%, coronary artery disease by 6%, and the risk of stroke by 15%” (CMAJ 2009;181:605-609).
A recent analysis by Asaria et al (Lancet 2007; 370:2044-2053) demonstrated that 8.5 million deaths worldwide could be avoided (2006-2015) with public policies directed at reducing salt intake.
It has been suggested, and exemplified by Finland, that for a population-based sodium reduction to occur there must be a partnership formed with the food industry. Finland began to have a countrywide sodium reduction in the 1970’s that resulted in a 40% decrease in sodium intake and a 70% reduction in mortality from stroke and coronary artery disease (Prog Cardiovasc Dis 2006;49:59-75). Other countries such as the United Kingdom, France, and Canada have begun similar programs.
In the new Affordable Care Act, a key indicator of the National Prevention Strategy is to reduce the average daily sodium intake in the United States population from the current 3,641mg to 2,300 mg within 10 years. This goal is in line with the Institute of Medicine, which set the “upper tolerable intake” for adults at 2,300 mg, the World Health Organization goal of 2000 mg or less daily, and the United Kingdom goal of 2,400 mg daily.
As health care providers we must work with our patients to identify foods (both processed and fresh) that are lower in sodium; support food manufacturers that lower sodium without raising other potentially harmful additives (potassium or phosphorus); and advocate for government controlled food labeling that gives clear and accurate nutrient information.
Lowering salt is an inexpensive, practical way to have a major impact on population health, mortality and overall health care costs. It behooves the health care community to stand up and loudly applaud this initiative within the Affordable Care Act, but even more so to engage in activities which will ensure its success.