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Shaking up the Conventional Wisdom on Salt

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Title

Shaking up the Conventional Wisdom on Salt

What Science Really Says about Sodium and Hypertension

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The notion that if you eat too much salt you will have high blood pressure has been perceived as medical gospel that most people—including this author—believed for the past three decades. But in recent years, research has emerged that challenges this once accepted truth. Headlines asking, “Is salt really bad for your blood pressure?” and declaring, “It’s time to end the war on salt,” have fostered growing suspicion among the public that the facts about salt and its effects on health might not be as clear cut as once believed.

Around the world, chronically elevated blood pressure affects approximately 40 percent of the adult population. In the United States, nearly one in three adults qualifies as hypertensive, which puts individuals at greater risk for many serious health events, including heart attack, heart failure, and stroke.

Considering the cost of the disease, both in terms of human suffering and the burden it places on our health care system, government agencies have made reducing the prevalence of hypertension a top priority. A public health strategy that successfully reduces hypertension rates has the potential to improve millions of lives and save millions of dollars. A misguided approach, on the other hand, would at best fail to reduce hypertension; at worst it would encourage behavioral changes that increase harm, obscure more effective means of risk reduction, and erode public trust in agencies.

For these reasons, population-wide recommendations should be rare and adhere to rigorous standards. At a minimum, such recommendations should:

  • Be limited in scope and based on robust, high-quality evidence;
  • Weigh and thoroughly consider unintended consequences; and
  • Be more effective and less harmful than the likely alternatives.

Based on a review of the scientific literature, the results of nearly four decades of government efforts focused on sodium restriction, and the existence of other—possible more effective—means of hypertension reduction as presented in this paper, the current government recommendations on sodium fail to meet this standard.

Key findings of this study include the following:

  • Humans require a certain amount of dietary sodium in order for our bodies to regulate fluid homeostasis. Too little sodium will result in the body ceasing to function, while too much can cause strain and death. However, the scientific community has yet to agree on an optimal range of sodium intake.
  • At least in part, the factors that determine what amount of salt a person craves (“salt appetite”) may be determined biologically and influence a person’s eating behavior in unconscious ways, making it resistant to public policy efforts to lower sodium intake (which may prompt undesirable physiological responses and changes in behavior).
  • Currently, government health agencies such as the U.S. Department of Health and Human Services, U.S. Department of Agriculture, and Centers for Disease Control and Prevention recommend adults consume less than 2,300 milligrams of sodium per day. This limit originated not from a process of scientific consultation, but from government fiat, prompted by politicians, bureaucrats, and industry.
  • Most human populations consume a relatively similar level of sodium that is much higher than the U.S. government recommendation, while only a handful of populations—some isolated tribal and Sub-Saharan peoples—consume less than 2,300 milligrams a day.
  • Americans have not significantly increased sodium intake since such investigations began in the 1950s. This is despite increases in processed food consumption, more sodium in processed food, and significant increases in both calorie consumption and average weight.
  • Lowering sodium can lower blood pressure for some people, but the response may only be seen at a certain extreme consumption level and is heterogeneous. When sodium is decreased, some individuals will experience decreases in blood pressure, some will experience no change, and some will see their blood pressure increase.
  • Scientific evidence is inconsistent regarding the health benefits of moderate sodium restriction for individuals who are not hypertensive.
  • People do not die as a result of high blood pressure, but rather from health effects linked to, but not necessarily caused by elevated blood pressure. As a corollary, blood pressure reduction does not always result in improved health outcomes.
  • Diets consisting of sodium levels lower than the recommended level are associated with negative health outcomes, though the cause of this association is unclear.
  • There is almost universal agreement within the scientific literature that other dietary factors, such as weight loss and increasing potassium intake, are as effective as sodium reduction in reducing blood pressure. Such alternative strategies also appear to be beneficial for a larger portion of the population,  have a greater probability of adherence, and have less chance of unintended consequences.

Worldwide, government attempts to lower population sodium intake below the recommended limit have failed despite four decades of effort. Considering this failure and what we currently know—and do not know—about the biological effect of sodium restriction on the population at large, government health agencies engaged in efforts to lower hypertension rates should abandon their myopic and ultimately futile war on salt.

The development of high blood pressure is personal, multifactorial, not influenced by a single genetic or lifestyle factor; sodium reduction may be advisable for some, but ineffective or counterproductive for others. The most effective approach for risk reduction can only be made on an individual basis by patients and their health care providers. However, if the government is going to attempt to lower population hypertension rates, it should refocus its efforts toward helping people lose weight and increase potassium in their diet with higher consumption of fruit and vegetables. Compared with salt-centric approach, this strategy would have a firmer grounding in science, be less likely to cause unintended harm, and may even have health benefits in addition to lowering blood pressure.