COMMENTARY
The Sodium Debate: More or Less About More or Less David L. Katz, MD, MPH
A
nother week, another roiling debate about nutrition. In the immortal words of Iago the parrot, “I think I’m gonna have a heart attack and die from that surprise!”1 Actually, heart attacks are directly germane to this topic—strokes even more so. The particular goal of guidelines addressing salt (or sodium)2 intake is to prevent ambient high blood pressure, a major contributor to cardiovascular disease and the leading cause of stroke. There are numerous other health effects of sodium intake as well, including an influence on bone density, but blood pressure tends to grab the spotlight. And spotlight it is at the moment. Recent studies have reached almost shockingly divergent conclusions about the pros and cons of sodium restriction. Compounding matters, the studies in question appeared in the very same issue of the New England Journal of Medicine,3,4,5 published on August 14, 2014. Two articles3,4 by the same large, international group of researchers called the “PURE investigators,” standing for the “Prospective Urban Rural Epidemiology”6 study, challenged the current emphasis on restricting sodium. Or at least that’s what the related headlines say.7 One of these studies looked at variation in sodium excretion in urine and its association with blood pressure3; the other looked at the same measure and its association with allcause mortality and cardiovascular disease.4 For both of these studies, the authors used a database of morning urine specimens from more than 100 000 people in 18 countries to estimate 24-hour sodium and potassium excretion, and from those estimated values, to extrapolate daily intake of sodium and potassium. We may leave the methods at that, other than noting that as estimates are predicated on estimates, the error bars get pretty wide, pretty fast. As noted, the inevitably hyperbolic headlines attached to these studies suggest they found that we should abandon salt restriction and pour it on. But here are the authors’ conclusions in their own words. In the first of the studies, they stated, Katz—Sodium
In this study, the association of estimated intake of sodium and potassium, as determined from measurements of excretion of these cations, with blood pressure was nonlinear and was most pronounced in persons consuming highsodium diets, persons with hypertension, and older persons.”5
If you think that’s a long way from “pour it on,”7 well—I agree. Essentially, the researchers found that excess sodium was most likely to raise blood pressure in older people and those already prone to high blood pressure. And, high sodium intake was most important when sodium intake was … high. Well, alrighty then. Moving on. The second study concluded with this: In this study in which sodium intake was estimated on the basis of measured urinary excretion, an estimated sodium intake between 3 g per day and 6 g per day was associated with a lower risk of death and cardiovascular events than was either a higher or lower estimated level of intake.4
Superficially, that translates to: We can eat too much salt, and we can eat too little.8 That we have long known, because sodium is an essential nutrient. Too little can result in a life-threatening condition called hyponatremia. The study may have raised questions about how much is too much, since the 3-gram threshold is higher than current recommendations, although not higher than prevailing intake. But we have to be careful not to overinterpret that isolated finding. What does it mean if your intake of sodium is lower than average for the population of which you are a member? It means you are different. That may be good, but it could readily be bad. Being “different” may mean not fitting in with prevailing norms for any number of reasons, from poor health to social isolation. A lower daily intake of salt could result merely from a lower daily intake of food. Where any of these factors is operative, they might account for variations in both blood pressure and mortality, quite independently of sodium. Wherever these first 2 two studies left us, we couldn’t stay there long, because the third study5 followed immediately after to shake things up some more. This one, Integrative Medicine • Vol. 13, No. 5 • October 2014
29
by a different group of investigators, obtained data on sodium intake and cardiovascular death for more than 70% of the global population of adults. What’s good for the goose is good for the gander, so here is what these researchers concluded: “In this modeling study, 1.65 million deaths from cardiovascular causes that occurred in 2010 were attributed to sodium consumption above a reference level of 2.0 g per day.”5 They went on to note that excess sodium intake was responsible for 1 in 10 of all deaths from cardiovascular disease around the globe. Associated headlines either indicated that our salt intake is, indeed, too high9; or more bluntly, that too much salt is killing us.10 A pretty confusing batch of papers, to say the least, and that, too, has made headlines.11 Here’s where I think it all shakes out: (1) There is no doubt it’s possible to consume too little sodium, and there is no doubt it’s possible to consume too much. (2) Not everyone is equally sensitive to sodium excess, and in general, it matters more as we age and to those of us prone to high blood pressure. (3) A lower intake of sodium than prevails in a given population might indicate other important differences in behavior, health, or social integration. The current studies account for these imperfectly. (4) The studies purportedly raising questions about the importance of sodium restriction are actually only challenging the optimal threshold, suggesting it should perhaps be 3 grams daily rather than the current World Health Organization recommendation of 2 grams daily.12 (5) Missing from all headlines is this important tidbit: More than twice as many adults4 have a sodium intake more than 6 grams daily as have an intake of less than 3 grams daily; and nearly 7 times as many4 have an intake more than 4 grams as have an intake of less than 3 grams. This, in my view, leads to the first key point: It is theoretically possible to consume too little sodium, but whether the relevant cut-point is set high or low, the vast majority of adults living in the real world consume too much. All 3 studies actually agreed on this point. So, yes, I presume if you fill a house with water, it might cause drowning. But I’m not sure that theoretical concern is of great practical value when putting out a fire. The second key point, certainly for those of us in the United States, is this: More than 75% of the sodium we consume comes from processed foods.13 This figures in the manipulation of recipes14 to maximize our calorie intake. The implications are rather clear. Any shift from a diet of more to less processed foods will result inevitably in a decrease in sodium intake. That shift is advisable 30
Integrative Medicine • Vol. 13, No. 5 • October 2014
because of the decisive health benefits associated with it, regardless of the specific contributions of sodium reduction to that benefit. A typical American diet tends to be too high in sodium whether the higher or lower cutpoint is invoked. But its more important liability is likely the fact that it is … typical American diet, in which onethird or more of calories routinely come from “junk.”15 There is no debate about the value of eating food in place of junk. As ever, competing headlines propagating confusion are partly a result of the legitimate nuances associated with the incremental advance of scientific understanding and partly the machinations of media16 profiting from hyperbole and intrigue. But we can bypass the potential confusion17 altogether if we take it all with the proverbial grain of salt. Whether the topic du jour18 is sodium or fructose; wheat or meat; gluten or saturated fat—we are subject to the impasse19 of perpetual confusion if we fixate sequentially on each successive study of each particular nutrient. If instead we embrace what we reliably know about healthful eating20 in general, sodium intake will tend to fall in the sweet spot,8 along with the intake of all other nutrients. In other words, we could reliably defend ourselves against hyperbole and headlines, malnutrition and misinformation alike—with wholesome foods, in sensible combinations.21 Tune in next week when that news … will be exactly the same.
References
1. Quotes for Iago. IMBd Web site. http://www.imdb.com/character/ ch0000624/quotes. Accessed August 29, 2014. 2. Salt. CDC Web site. http://www.cdc.gov/salt/. Accessed August 29, 2014. 3. Teo K, Chow CK, Vaz M. The Prospective Urban Rural Epidemiology (PURE) study: examining the impact of societal influences on chronic noncommunicable diseases in low-, middle-, and high-income countries. Am Heart J. 2009158(1):1-7.e1. 4. Pour on the salt? New research suggests more is okay. NBC Web site. http:// www.nbcnews.com/health/heart-health/pour-salt-new-research-suggestsmore-ok-n179941. Published August 13, 2014. Accessed August 29, 2014. 5. Mente A, O’Donnell MJ, Rangarajan S, et al. Association of urinary sodium and potassium excretion with blood pressure. N Engl J Med. August 2014;371:601-611. 6. O’Donnell M, Mente A, Rangarajan S, et al. Urinary sodium and potassium excretion, mortality, and cardiovascular events. N Engl J Med. August 2014;371:612-623. 7. Katz DL. Salt in the sweet spot: Why we still need to lower our salt intake. US News & World Report. May 20, 2013. http://health.usnews.com/health-news/ blogs/eat-run/2013/05/20/salt-in-the-sweet-spot. Accessed August 29, 2014. 8. Mozaffarian D, Fahimi S, Singh GM, et al. Global sodium consumption and death from cardiovascular causes. N Engl J Med. August 2014;371:624-634. 9. Bernstein L. Salt intake is too high in 181 of 187 countries around the world. Washington Post. August 14, 2014. http://www.washingtonpost.com/news/toyour-health/wp/2014/08/14/salt-intake-is-too-high-in-181-of-187-countriesaround-the-world/. Accessed August 29, 2014. 10. We’re eating too much salt. Vox Web site. http://w w w.vox. com/2014/8/17/6026431/were-eating-too-much-salt-and-its-killing-us. Updated August 17, 2014. Accessed August 29, 2014 11. Sifferlin A. Serious salt confusion: New research on how much salt you should eat. Time. August 15, 2014. http://time.com/#3111947/serious-saltconfusion-new-research-on-how-much-salt-you-should-eat/. Accessed August 29, 2014. 12. World Health Organization. Guideline: Sodium intake for adults and children. http://apps.who.int/iris/bitstream/10665/77985/1/9789241504836_eng. pdf?ua=1. Published 2012. Accessed August 29, 2014.
Katz—Sodium
13. Processed foods: Where is all that salt coming from? American Heart Association Web site. http://www.heart. org/HEARTORG/Conditions/HighBloodPressure/ PreventionTreatmentofHighBloodPressure/ProcessedFoods-Where-is-all-that-salt-coming-from_ UCM_426950_Article.jsp. Updated May 1, 2014. Accessed August 29, 2014. 14. Moss M. The extraordinary science of addictive junk food. New York Times. February 20, 2013. http://www. nytimes.com/2013/02/24/magazine/the-extraordinaryscience-of-junk-food.html?pagewanted=all&_r=1&. Accessed August 29, 2014. 15. Katz DL. Should ‘junk’ really be a food group? Love the food that loves you back. US News & World Report. March 24, 2013. http://health.usnews.com/health-news/blogs/ eat-run/2013/03/24/should-junk-really-be-a-food-group. Accessed August 29, 2014. 16. Katz D. Our comfortable affliction. Huffington Post. March 25, 2013. http://www.huffingtonpost.com/davidkatz-md/media-health-coverage_b_2937624.html. Accessed August 29, 2013. 17. Katz DL. Diet, weight, and health: Confused only if you want to be! LinkedIn Web site. https://www.linkedin.com/ today/post/article/20140209153920-23027997-dietweight-and-health-confused-only-if-you-want-tobe?trk=mp-reader-card. Published February 9, 2014. Accessed August 29, 2014. 18. Katz DL. Author profile. LinkedIn Web site. https://www. linkedin.com/today/author/23027997. Accessed August 29, 2014. 19. Katz DL. Health at an Impasse: The case for getting past collusion. LinkedIn Web site. https://www.linkedin.com/ today/post/article/20131115135751-23027997-health-atan-impasse-the-case-for-getting-past-collusion. Published November 15, 2013. Accessed August 29, 2014. 20. Katz DL, Meller S. Can we say what diet is best for health? Ann Rev Public Health. March 2014;35:83-103. 21. Hamblin J. Science compared every diet, and the winner is real food. The Atlantic. March 24, 2014. http://www.theatlantic.com/health/archive/2014/03/science-comparedever y-diet-and-the-winner-is-real-food/284595/. Accessed August 29, 2014.
The Sodium Debate: More or Less About More or Less David L. Katz, MD, MPH
A
nother week, another roiling debate about nutrition. In the immortal words of Iago the parrot, “I think I’m gonna have a heart attack and die from that surprise!”1 Actually, heart attacks are directly germane to this topic—strokes even more so. The particular goal of guidelines addressing salt (or sodium)2 intake is to prevent ambient high blood pressure, a major contributor to cardiovascular disease and the leading cause of stroke. There are numerous other health effects of sodium intake as well, including an influence on bone density, but blood pressure tends to grab the spotlight. And spotlight it is at the moment. Recent studies have reached almost shockingly divergent conclusions about the pros and cons of sodium restriction. Compounding matters, the studies in question appeared in the very same issue of the New England Journal of Medicine,3,4,5 published on August 14, 2014. Two articles3,4 by the same large, international group of researchers called the “PURE investigators,” standing for the “Prospective Urban Rural Epidemiology”6 study, challenged the current emphasis on restricting sodium. Or at least that’s what the related headlines say.7 One of these studies looked at variation in sodium excretion in urine and its association with blood pressure3; the other looked at the same measure and its association with allcause mortality and cardiovascular disease.4 For both of these studies, the authors used a database of morning urine specimens from more than 100 000 people in 18 countries to estimate 24-hour sodium and potassium excretion, and from those estimated values, to extrapolate daily intake of sodium and potassium. We may leave the methods at that, other than noting that as estimates are predicated on estimates, the error bars get pretty wide, pretty fast. As noted, the inevitably hyperbolic headlines attached to these studies suggest they found that we should abandon salt restriction and pour it on. But here are the authors’ conclusions in their own words. In the first of the studies, they stated, Katz—Sodium
In this study, the association of estimated intake of sodium and potassium, as determined from measurements of excretion of these cations, with blood pressure was nonlinear and was most pronounced in persons consuming highsodium diets, persons with hypertension, and older persons.”5
If you think that’s a long way from “pour it on,”7 well—I agree. Essentially, the researchers found that excess sodium was most likely to raise blood pressure in older people and those already prone to high blood pressure. And, high sodium intake was most important when sodium intake was … high. Well, alrighty then. Moving on. The second study concluded with this: In this study in which sodium intake was estimated on the basis of measured urinary excretion, an estimated sodium intake between 3 g per day and 6 g per day was associated with a lower risk of death and cardiovascular events than was either a higher or lower estimated level of intake.4
Superficially, that translates to: We can eat too much salt, and we can eat too little.8 That we have long known, because sodium is an essential nutrient. Too little can result in a life-threatening condition called hyponatremia. The study may have raised questions about how much is too much, since the 3-gram threshold is higher than current recommendations, although not higher than prevailing intake. But we have to be careful not to overinterpret that isolated finding. What does it mean if your intake of sodium is lower than average for the population of which you are a member? It means you are different. That may be good, but it could readily be bad. Being “different” may mean not fitting in with prevailing norms for any number of reasons, from poor health to social isolation. A lower daily intake of salt could result merely from a lower daily intake of food. Where any of these factors is operative, they might account for variations in both blood pressure and mortality, quite independently of sodium. Wherever these first 2 two studies left us, we couldn’t stay there long, because the third study5 followed immediately after to shake things up some more. This one, Integrative Medicine • Vol. 13, No. 5 • October 2014
29
by a different group of investigators, obtained data on sodium intake and cardiovascular death for more than 70% of the global population of adults. What’s good for the goose is good for the gander, so here is what these researchers concluded: “In this modeling study, 1.65 million deaths from cardiovascular causes that occurred in 2010 were attributed to sodium consumption above a reference level of 2.0 g per day.”5 They went on to note that excess sodium intake was responsible for 1 in 10 of all deaths from cardiovascular disease around the globe. Associated headlines either indicated that our salt intake is, indeed, too high9; or more bluntly, that too much salt is killing us.10 A pretty confusing batch of papers, to say the least, and that, too, has made headlines.11 Here’s where I think it all shakes out: (1) There is no doubt it’s possible to consume too little sodium, and there is no doubt it’s possible to consume too much. (2) Not everyone is equally sensitive to sodium excess, and in general, it matters more as we age and to those of us prone to high blood pressure. (3) A lower intake of sodium than prevails in a given population might indicate other important differences in behavior, health, or social integration. The current studies account for these imperfectly. (4) The studies purportedly raising questions about the importance of sodium restriction are actually only challenging the optimal threshold, suggesting it should perhaps be 3 grams daily rather than the current World Health Organization recommendation of 2 grams daily.12 (5) Missing from all headlines is this important tidbit: More than twice as many adults4 have a sodium intake more than 6 grams daily as have an intake of less than 3 grams daily; and nearly 7 times as many4 have an intake more than 4 grams as have an intake of less than 3 grams. This, in my view, leads to the first key point: It is theoretically possible to consume too little sodium, but whether the relevant cut-point is set high or low, the vast majority of adults living in the real world consume too much. All 3 studies actually agreed on this point. So, yes, I presume if you fill a house with water, it might cause drowning. But I’m not sure that theoretical concern is of great practical value when putting out a fire. The second key point, certainly for those of us in the United States, is this: More than 75% of the sodium we consume comes from processed foods.13 This figures in the manipulation of recipes14 to maximize our calorie intake. The implications are rather clear. Any shift from a diet of more to less processed foods will result inevitably in a decrease in sodium intake. That shift is advisable 30
Integrative Medicine • Vol. 13, No. 5 • October 2014
because of the decisive health benefits associated with it, regardless of the specific contributions of sodium reduction to that benefit. A typical American diet tends to be too high in sodium whether the higher or lower cutpoint is invoked. But its more important liability is likely the fact that it is … typical American diet, in which onethird or more of calories routinely come from “junk.”15 There is no debate about the value of eating food in place of junk. As ever, competing headlines propagating confusion are partly a result of the legitimate nuances associated with the incremental advance of scientific understanding and partly the machinations of media16 profiting from hyperbole and intrigue. But we can bypass the potential confusion17 altogether if we take it all with the proverbial grain of salt. Whether the topic du jour18 is sodium or fructose; wheat or meat; gluten or saturated fat—we are subject to the impasse19 of perpetual confusion if we fixate sequentially on each successive study of each particular nutrient. If instead we embrace what we reliably know about healthful eating20 in general, sodium intake will tend to fall in the sweet spot,8 along with the intake of all other nutrients. In other words, we could reliably defend ourselves against hyperbole and headlines, malnutrition and misinformation alike—with wholesome foods, in sensible combinations.21 Tune in next week when that news … will be exactly the same.
References
1. Quotes for Iago. IMBd Web site. http://www.imdb.com/character/ ch0000624/quotes. Accessed August 29, 2014. 2. Salt. CDC Web site. http://www.cdc.gov/salt/. Accessed August 29, 2014. 3. Teo K, Chow CK, Vaz M. The Prospective Urban Rural Epidemiology (PURE) study: examining the impact of societal influences on chronic noncommunicable diseases in low-, middle-, and high-income countries. Am Heart J. 2009158(1):1-7.e1. 4. Pour on the salt? New research suggests more is okay. NBC Web site. http:// www.nbcnews.com/health/heart-health/pour-salt-new-research-suggestsmore-ok-n179941. Published August 13, 2014. Accessed August 29, 2014. 5. Mente A, O’Donnell MJ, Rangarajan S, et al. Association of urinary sodium and potassium excretion with blood pressure. N Engl J Med. August 2014;371:601-611. 6. O’Donnell M, Mente A, Rangarajan S, et al. Urinary sodium and potassium excretion, mortality, and cardiovascular events. N Engl J Med. August 2014;371:612-623. 7. Katz DL. Salt in the sweet spot: Why we still need to lower our salt intake. US News & World Report. May 20, 2013. http://health.usnews.com/health-news/ blogs/eat-run/2013/05/20/salt-in-the-sweet-spot. Accessed August 29, 2014. 8. Mozaffarian D, Fahimi S, Singh GM, et al. Global sodium consumption and death from cardiovascular causes. N Engl J Med. August 2014;371:624-634. 9. Bernstein L. Salt intake is too high in 181 of 187 countries around the world. Washington Post. August 14, 2014. http://www.washingtonpost.com/news/toyour-health/wp/2014/08/14/salt-intake-is-too-high-in-181-of-187-countriesaround-the-world/. Accessed August 29, 2014. 10. We’re eating too much salt. Vox Web site. http://w w w.vox. com/2014/8/17/6026431/were-eating-too-much-salt-and-its-killing-us. Updated August 17, 2014. Accessed August 29, 2014 11. Sifferlin A. Serious salt confusion: New research on how much salt you should eat. Time. August 15, 2014. http://time.com/#3111947/serious-saltconfusion-new-research-on-how-much-salt-you-should-eat/. Accessed August 29, 2014. 12. World Health Organization. Guideline: Sodium intake for adults and children. http://apps.who.int/iris/bitstream/10665/77985/1/9789241504836_eng. pdf?ua=1. Published 2012. Accessed August 29, 2014.
Katz—Sodium
13. Processed foods: Where is all that salt coming from? American Heart Association Web site. http://www.heart. org/HEARTORG/Conditions/HighBloodPressure/ PreventionTreatmentofHighBloodPressure/ProcessedFoods-Where-is-all-that-salt-coming-from_ UCM_426950_Article.jsp. Updated May 1, 2014. Accessed August 29, 2014. 14. Moss M. The extraordinary science of addictive junk food. New York Times. February 20, 2013. http://www. nytimes.com/2013/02/24/magazine/the-extraordinaryscience-of-junk-food.html?pagewanted=all&_r=1&. Accessed August 29, 2014. 15. Katz DL. Should ‘junk’ really be a food group? Love the food that loves you back. US News & World Report. March 24, 2013. http://health.usnews.com/health-news/blogs/ eat-run/2013/03/24/should-junk-really-be-a-food-group. Accessed August 29, 2014. 16. Katz D. Our comfortable affliction. Huffington Post. March 25, 2013. http://www.huffingtonpost.com/davidkatz-md/media-health-coverage_b_2937624.html. Accessed August 29, 2013. 17. Katz DL. Diet, weight, and health: Confused only if you want to be! LinkedIn Web site. https://www.linkedin.com/ today/post/article/20140209153920-23027997-dietweight-and-health-confused-only-if-you-want-tobe?trk=mp-reader-card. Published February 9, 2014. Accessed August 29, 2014. 18. Katz DL. Author profile. LinkedIn Web site. https://www. linkedin.com/today/author/23027997. Accessed August 29, 2014. 19. Katz DL. Health at an Impasse: The case for getting past collusion. LinkedIn Web site. https://www.linkedin.com/ today/post/article/20131115135751-23027997-health-atan-impasse-the-case-for-getting-past-collusion. Published November 15, 2013. Accessed August 29, 2014. 20. Katz DL, Meller S. Can we say what diet is best for health? Ann Rev Public Health. March 2014;35:83-103. 21. Hamblin J. Science compared every diet, and the winner is real food. The Atlantic. March 24, 2014. http://www.theatlantic.com/health/archive/2014/03/science-comparedever y-diet-and-the-winner-is-real-food/284595/. Accessed August 29, 2014.
