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Potassium in Food Additives: Something Else to Consider
EDITORIAL
Potassium in Food Additives: Something Else to Consider
T
HE CONTRIBUTION OF FOOD additives to the dietary-phosphate burden of patients with chronic kidney disease (CKD) has become an area of increased recognition and concern in recent years.1–4 In addition to their effect on phosphate, food additives also add substantially to the sodium content of foods, another concern for CKD patients as well as many in the general population. Yet another effect of these additives, and one that is still largely unrecognized in the literature, involves their impact on the dietary potassium burden. The contribution of additives to a food’s potassium content can be substantial. We recently reported that uncooked, enhanced (i.e., containing additives) meat and poultry products had levels of potassium that were up to threefold greater than in similar unenhanced food products.5 We found the variability of potassium content in these enhanced products to be far greater than that of their phosphorus content. The basis for this observation probably rests on the choice of phosphate salts used as additives. Phosphate salts differ in their effects on meat products. For example, more alkaline phosphates (e.g., trisodium phosphates and tetrasodium pyrophosphate) increase the water-holding capacity of meats more than do acid phosphates (e.g., sodium acid pyrophosphate). Potassium tripolyphosphate, tetrapotassium phosphate, and sodium hexametaphosphate are more hydroscopic than sodium trypolyphosphate and tetrasodium pyrophosphate. Tetrapotassium pyrophosphate is more soluble in water than tetrasodium pyrophosphate, which This report was supported by unrestricted educational grants from Dialysis Clinics, Inc. and Genzyme, Inc. Address reprint requests to Richard A. Sherman, MD, Division of Nephrology, Department of Medicine, University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, One Robert Wood Johnson Place, PO Box 19, New Brunswick, NJ 08901. E-mail: [email protected]. Ó 2009 by the National Kidney Foundation, Inc. All rights reserved. 1051-2276/09/1906-0001$36.00/0 doi:10.1053/j.jrn.2009.08.010
Journal of Renal Nutrition, Vol 19, No 6 (November), 2009: 441–442
would favor the use of the former in many settings. Eleven phosphate salts are approved for use in meat products in the United States. This number may appear low, but is explained by the multiple names given to specific salts. For example, dipotassium phosphate is also called DKP, dipotassium monohydrogen orthophosphate, and potassium phosphate dibasic. Five of the approved phosphate additives for meat are potassium salts. Thus, the salts used in enhancing meat products may make no contribution to the potassium content of a product if only sodium salts are used. Thus, Granger’s beef filet of sirloin (enhanced) had essentially the identical amount of potassium (331 mg/ 100 g) as an unenhanced supermarket sirloin steak (328 mg/100 g), whereas the phosphate-content and phosphate/protein ratios were 39% higher (250 vs. 180 mg/100 g) and 55% higher (12.8 vs. 8.5 mg/g protein), respectively. In contrast, an enhanced beef boneless strip steak had three times more potassium (930 mg/100 g) than an unenhanced version (311 mg/100 g), despite differences in phosphate content that were comparable to those of the sirloin steaks noted above.5 Cheese is certainly on the list of foods to avoid because of its high phosphorus content. However, its contribution to dietary potassium is little appreciated. Although cheddar cheese (Kraft Sharp Cracker Barrel) had only 92 mg/100 g of potassium, the same manufacturer’s American Singles and Velveeta products had 319 and 389 mg/100 g of potassium, respectively (unpublished observations). Beef frankfurters further illustrate the discordance between increases in potassium and phosphate attributable to food additives. Oscar Meyer and Ballpark both contain phosphate additives, whereas Sabrett does not.6 However, Oscar Meyer and Sabrett have similar amounts of potassium (181 and 177 mg/100 g, respectively), whereas Ballpark has far more potassium (430 mg/100 g; unpublished observations). In some cases, the data turned common wisdom on its head. The less processed Wise potato 441
442
EDITORIAL
chips have almost twice the potassium (1150 mg/ 100 g) as a manufactured potato chip (Pringles, 646 mg/100 g). Fast food, recognized as contributing substantially to the dietary phosphate burden,7 is also problematic with respect to potassium. Panera’s chicken chipotle sandwich on French bread had more than twice the potassium content of Wendy’s chicken filet sandwich (421 vs. 184 mg/100 g, respectively). White Castle French Fries had 47% more potassium than those of Burger King (584 vs. 397 mg/100 g, respectively; unpublished observations). The issue of potassium-containing additives is clearly important. Hyperkalemia is a significant cause of mortality in dialysis patients, as well as in CKD patients not on dialysis.8,9 The 2114 mg of potassium in 8 ounces of enhanced beef strip steak by itself exceeds the daily prescribed dietary potassium of many patients, and might go unrecognized as an etiologic factor in any associated hyperkalemia. What can be done? As matters currently stand, attention to food labels is useful. When specific additives are listed, attention should be paid to whether these include potassium salts. When specific ingredients are omitted from foods that contain additives (typically accompanied by terms such as ‘‘enhanced with a natural solution of.’’), the food should be considered potentially problematic. Fast-food purveyors usually make available on their company’s website (and sometimes in brochures at the restaurants) information available on food additives in their products. Although the quantity of potassium added will generally not be available, a mental ‘‘warning bell’’ should go off when potassium additives are noted. The long-tem (and better) solution is to include the potassium content of foods on the nutrition label. A less satisfactory, but reasonable, option would be to require manufacturers who add potassium to food to label that food with its
potassium content. With the increasing incidence of CKD and the use of medications that impair renal potassium excretion, the value of this information to the general public is growing. In our view, strong consideration should be given by regulatory agencies to require that these data be made available in a readily accessible manner. Richard A. Sherman, MD Ojas Mehta, DO Division of Nephrology, Department of Medicine University of Medicine and Dentistry of New Jersey Robert Wood Johnson Medical School, New Brunswick New Jersey
References 1. Uribarri J: Phosphorus homeostasis in chronic kidney disease patients with special emphasis on dietary phosphorus intake. Semin Dial 20:295–301, 2007. 2. Sherman RA: Dietary phosphate restriction and protein intake in dialysis patients: A misdirected focus. Semin Dial 20: 16–18, 2007. 3. Sullivan CM, Leon JB, Machekano R, et al: Effect of food additives on hyperphosphatemia among patients with end-stage renal disease. JAMA 301:629–635, 2009. 4. Kestenbaum B: Phosphate metabolism in the setting of chronic kidney disease: Significance and recommendations for treatment. Semin Dial 20:286–294, 2007. 5. Sherman RA, Mehta O: Phosphorus and potassium content of enhanced meat and poultry products: Implications for patients who receive dialysis. Clin J Am Soc Nephrol 4:1370–1373, 2009. 6. Sherman RA, Mehta O: Dietary phosphorus restriction in dialysis patients: Potential impact of processed meat, poultry, and fish products as protein sources. Am J Kidney Dis 54:18–23, 2009. 7. Srilekha S, Sullivan C, Leon JB, Sehgal AR: Fast food, phosphorus-containing additives, and the renal diet. J Ren Nutr 18: 466–470, 2008. 8. Einhorn LM, Zhan M, Hsu VD, et al: The frequency of hyperkalemia and its significance in chronic kidney disease. Arch Intern Med 169:1156–1162, 2009. 9. Genovesi S, Valsecchi MG, Rossi E, et al: Sudden death and associated factors in a historical cohort of chronic hemodialysis patients. Nephrol Dial Transplant 24:2529–2536, 2009.
Potassium in Food Additives: Something Else to Consider
T
HE CONTRIBUTION OF FOOD additives to the dietary-phosphate burden of patients with chronic kidney disease (CKD) has become an area of increased recognition and concern in recent years.1–4 In addition to their effect on phosphate, food additives also add substantially to the sodium content of foods, another concern for CKD patients as well as many in the general population. Yet another effect of these additives, and one that is still largely unrecognized in the literature, involves their impact on the dietary potassium burden. The contribution of additives to a food’s potassium content can be substantial. We recently reported that uncooked, enhanced (i.e., containing additives) meat and poultry products had levels of potassium that were up to threefold greater than in similar unenhanced food products.5 We found the variability of potassium content in these enhanced products to be far greater than that of their phosphorus content. The basis for this observation probably rests on the choice of phosphate salts used as additives. Phosphate salts differ in their effects on meat products. For example, more alkaline phosphates (e.g., trisodium phosphates and tetrasodium pyrophosphate) increase the water-holding capacity of meats more than do acid phosphates (e.g., sodium acid pyrophosphate). Potassium tripolyphosphate, tetrapotassium phosphate, and sodium hexametaphosphate are more hydroscopic than sodium trypolyphosphate and tetrasodium pyrophosphate. Tetrapotassium pyrophosphate is more soluble in water than tetrasodium pyrophosphate, which This report was supported by unrestricted educational grants from Dialysis Clinics, Inc. and Genzyme, Inc. Address reprint requests to Richard A. Sherman, MD, Division of Nephrology, Department of Medicine, University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, One Robert Wood Johnson Place, PO Box 19, New Brunswick, NJ 08901. E-mail: [email protected]. Ó 2009 by the National Kidney Foundation, Inc. All rights reserved. 1051-2276/09/1906-0001$36.00/0 doi:10.1053/j.jrn.2009.08.010
Journal of Renal Nutrition, Vol 19, No 6 (November), 2009: 441–442
would favor the use of the former in many settings. Eleven phosphate salts are approved for use in meat products in the United States. This number may appear low, but is explained by the multiple names given to specific salts. For example, dipotassium phosphate is also called DKP, dipotassium monohydrogen orthophosphate, and potassium phosphate dibasic. Five of the approved phosphate additives for meat are potassium salts. Thus, the salts used in enhancing meat products may make no contribution to the potassium content of a product if only sodium salts are used. Thus, Granger’s beef filet of sirloin (enhanced) had essentially the identical amount of potassium (331 mg/ 100 g) as an unenhanced supermarket sirloin steak (328 mg/100 g), whereas the phosphate-content and phosphate/protein ratios were 39% higher (250 vs. 180 mg/100 g) and 55% higher (12.8 vs. 8.5 mg/g protein), respectively. In contrast, an enhanced beef boneless strip steak had three times more potassium (930 mg/100 g) than an unenhanced version (311 mg/100 g), despite differences in phosphate content that were comparable to those of the sirloin steaks noted above.5 Cheese is certainly on the list of foods to avoid because of its high phosphorus content. However, its contribution to dietary potassium is little appreciated. Although cheddar cheese (Kraft Sharp Cracker Barrel) had only 92 mg/100 g of potassium, the same manufacturer’s American Singles and Velveeta products had 319 and 389 mg/100 g of potassium, respectively (unpublished observations). Beef frankfurters further illustrate the discordance between increases in potassium and phosphate attributable to food additives. Oscar Meyer and Ballpark both contain phosphate additives, whereas Sabrett does not.6 However, Oscar Meyer and Sabrett have similar amounts of potassium (181 and 177 mg/100 g, respectively), whereas Ballpark has far more potassium (430 mg/100 g; unpublished observations). In some cases, the data turned common wisdom on its head. The less processed Wise potato 441
442
EDITORIAL
chips have almost twice the potassium (1150 mg/ 100 g) as a manufactured potato chip (Pringles, 646 mg/100 g). Fast food, recognized as contributing substantially to the dietary phosphate burden,7 is also problematic with respect to potassium. Panera’s chicken chipotle sandwich on French bread had more than twice the potassium content of Wendy’s chicken filet sandwich (421 vs. 184 mg/100 g, respectively). White Castle French Fries had 47% more potassium than those of Burger King (584 vs. 397 mg/100 g, respectively; unpublished observations). The issue of potassium-containing additives is clearly important. Hyperkalemia is a significant cause of mortality in dialysis patients, as well as in CKD patients not on dialysis.8,9 The 2114 mg of potassium in 8 ounces of enhanced beef strip steak by itself exceeds the daily prescribed dietary potassium of many patients, and might go unrecognized as an etiologic factor in any associated hyperkalemia. What can be done? As matters currently stand, attention to food labels is useful. When specific additives are listed, attention should be paid to whether these include potassium salts. When specific ingredients are omitted from foods that contain additives (typically accompanied by terms such as ‘‘enhanced with a natural solution of.’’), the food should be considered potentially problematic. Fast-food purveyors usually make available on their company’s website (and sometimes in brochures at the restaurants) information available on food additives in their products. Although the quantity of potassium added will generally not be available, a mental ‘‘warning bell’’ should go off when potassium additives are noted. The long-tem (and better) solution is to include the potassium content of foods on the nutrition label. A less satisfactory, but reasonable, option would be to require manufacturers who add potassium to food to label that food with its
potassium content. With the increasing incidence of CKD and the use of medications that impair renal potassium excretion, the value of this information to the general public is growing. In our view, strong consideration should be given by regulatory agencies to require that these data be made available in a readily accessible manner. Richard A. Sherman, MD Ojas Mehta, DO Division of Nephrology, Department of Medicine University of Medicine and Dentistry of New Jersey Robert Wood Johnson Medical School, New Brunswick New Jersey
References 1. Uribarri J: Phosphorus homeostasis in chronic kidney disease patients with special emphasis on dietary phosphorus intake. Semin Dial 20:295–301, 2007. 2. Sherman RA: Dietary phosphate restriction and protein intake in dialysis patients: A misdirected focus. Semin Dial 20: 16–18, 2007. 3. Sullivan CM, Leon JB, Machekano R, et al: Effect of food additives on hyperphosphatemia among patients with end-stage renal disease. JAMA 301:629–635, 2009. 4. Kestenbaum B: Phosphate metabolism in the setting of chronic kidney disease: Significance and recommendations for treatment. Semin Dial 20:286–294, 2007. 5. Sherman RA, Mehta O: Phosphorus and potassium content of enhanced meat and poultry products: Implications for patients who receive dialysis. Clin J Am Soc Nephrol 4:1370–1373, 2009. 6. Sherman RA, Mehta O: Dietary phosphorus restriction in dialysis patients: Potential impact of processed meat, poultry, and fish products as protein sources. Am J Kidney Dis 54:18–23, 2009. 7. Srilekha S, Sullivan C, Leon JB, Sehgal AR: Fast food, phosphorus-containing additives, and the renal diet. J Ren Nutr 18: 466–470, 2008. 8. Einhorn LM, Zhan M, Hsu VD, et al: The frequency of hyperkalemia and its significance in chronic kidney disease. Arch Intern Med 169:1156–1162, 2009. 9. Genovesi S, Valsecchi MG, Rossi E, et al: Sudden death and associated factors in a historical cohort of chronic hemodialysis patients. Nephrol Dial Transplant 24:2529–2536, 2009.