The Center for Disease Control’s (CDC’s) Morbidity and Mortality Weekly Report just published surveillance data on salt consumption among adults in the US: “Sodium Intake in Adults – United States, 2005-2006.” Almost all of us are consuming too much. How much salt is too much? Very little, more than a teaspoon a day is too much, and if you are a child or are elderly, it is way too much. While everyone salts (or doesn’t) their food differently, the food industry is adding about 75 percent of the sodium you consume. Almost every processed food has salt in it and some, like processed meats, some canned soups, snack foods, and fast food can deliver a day’s maximum recommendation, or more, in a single serving.
Unlike diets that are high in natural foods, diets based on processed foods have lots of sodium and little potassium. How big is the effect of a high sodium diet? Hypertension affects less than 1 percent of people in isolated societies, but about one-third of adults in industrialized societies. It is not just a high sodium problem; it is a low potassium problem. “One of the most prevalent and modifiable risk factors for hypertension is an inadequate consumption of potassium. Only about 2 percent of U.S. adults meet the current guideline for dietary potassium intake (at least 4.7 grams per day).” In combination, low potassium and high sodium consumption effects on blood pressure and resulting morbidity are enormous. Population studies have consistently shown that as potassium intake goes up, blood pressure goes down along with the prevalence of hypertension and the risk of stroke.
We are not made for a high sodium diet and our changing Western diet has far outstripped our bodies’ ability to accommodate too much sodium. Our kidneys are designed to preserve sodium and excrete potassium. In the tubules of the kidneys, sodium is reabsorbed and as sodium concentrations go up so does potassium excretion. This worked very well for our forbearers who had no processed foods to eat. It is a disaster for many of us today. As the CDC puts it:
“Current dietary guidelines for Americans recommend that adults in general should consume no more than 2,300 mg of sodium per day. At the same time, consume potassium-rich foods, such as fruits and vegetables. However, if you are in the following population groups, you should consume no more than 1,500 mg of sodium per day (approximately 2/3 teaspoon), and meet the potassium recommendation (4,700 mg/day) with food.
• You are 40 years of age or older.
• You are African American.
• You have high blood pressure.
“A CDC report shows that 2 out of 3 (69 percent) adults in the United States fall into these three groups who are at especially high risk for health problems from consuming too much sodium. Eating less sodium can help prevent, or control, high blood pressure.”
Our bodies spend considerable energy regulating the concentration of sodium and potassium in and out of our cells. You may recall the sodium/potassium pump (Na⁺/K⁺–ATPase) from high school biology that shuttles sodium ions into the cell and potassium ions out. When excess sodium is retained, sodium concentration goes up in cells of arterial smooth muscle cells and ultimately drives calcium into cells. The net effect is contraction of the smooth muscle and arteriolar vasodilatation. The resulting vascular resistance helps drive up pressure in tiny vessels.
Despite its well-demonstrated risks, dietary salt has resisted regulation. The double whammy of claims of Big Brother government in the kitchen and the salt-dependent food industry has so far saved salt from the fate of trans-fats and the current cut-back in added fructose. Yet it is easier to draw a straight line from too much salt to measurable deleterious health effects that with either trans-fats or fructose. When New York Mayor Michael Bloomberg recently called for food companies to reduce their salt in processed foods by 25 percent, he was hit with a withering barrage of criticism. Food industry giant Cargill meanwhile, can’t say enough about the wonders of salt and urges consumers to add it to everything from fresh fruit to ice cream.
It’s an interesting notion that compared to the world of foodborne pathogens, salt may indirectly account for far more excess deaths than any microbe. The CDC counted 23,855 deaths due to hypertension in 2006. If there were a foodborne bacterial agent killing 20,000 Americans a year one likes to think there would be a significant effort to limit that agent’s presence in food. With salt, the fight may just be beginning, though a significant reduction in the sodium content of processed foods is still not in sight.
As Food Safety News has reported, Mayor Bloomberg’s efforts to reduce sodium in the American diet resulted in The National Salt Reduction Initiative (NSRI), a public-private partnership which has enlisted a wide array of food manufacturers and restaurants. Still, the goals of the NSRI are modest: a 20 percent reduction in sodium in prepared foods over five years. Given the ubiquity of salt in processed foods, a top-down regulatory approach seems ill suited to address this public health issue. A combination of consumer awareness (including the need for increasing potassium consumption) and voluntary industry action may reduce our over-consumption, but is unlikely to solve the problem. With salt, the fight may just be beginning, and a reduction in the sodium content of processed foods sufficient to benefit the health of Americans is not yet in sight.
1. Consensus Report: “A Population-Based Policy and Systems Change Approach to Prevent and Control Hypertension” report brief, Board on Population Health and Public health Practice, Institute of Medicine of the National Academies: http://www.iom.edu/Reports/2010/A-Population-Based-Policy-and-Systems-Change-Approach-to-Prevent-and-Control-Hypertension.aspx.
2. See, http://www.cdc.gov/salt/.
3. Yes, the processes involved in hypertension are vastly more complicated and well beyond the scope of this article.
6. See, Flynn D, “Kraft, Subway, Starbucks to Cut Salt,” Food Safety News, April 29, 2010: https://www.foodsafetynews.com/2010/04/food-industry-taking-challenge-to-cut-salt/.
7. I wonder how long before the fresh fruit and produce industries tumble to the huge marketing opportunity posed by a hypertensive, potassium poor population.