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Strategies to Reduce Sodium Intake in the United States 8 Committee’s Considerations and Basis for Recommendations The committee’s general approach to identifying recommended strategies is illustrated in Figure 1-1 in Chapter 1. To identify recommended strategies for reducing sodium intake among the U.S. population, the committee considered the past initiatives and unique challenges described in Chapters 2 and 3. This information served as a stage-setting activity for the committee. Next, the committee considered the array of factors outlined in Chapters 4 through 7 ranging from the functional effects of sodium in foods to the food environment to regulatory options. The goal was to examine the lessons learned from past and current efforts to reduce sodium intake within the context of the available information about important factors in considering strategies to reduce sodium intake. The result provided an informed basis for identifying effective and sustainable strategies. The findings and considerations are discussed below. The recommended strategies are presented in Chapter 9. LESSONS LEARNED FROM CONSUMER-ORIENTED PUBLIC HEALTH INITIATIVES As described in Chapter 2, the committee reviewed campaigns and interventions initiated as early as the 1969 White House Conference on Food, Nutrition, and Health and continuing to the present. These activities are noteworthy for the number and range of organizations and initiatives that have worked to educate consumers about the importance of reducing sodium intake and impact their food choices to reduce intake. Over the past 40 years, government agencies, authoritative scientific bodies, and health professional organizations have set target goals for sodium intake and dis-
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Strategies to Reduce Sodium Intake in the United States seminated relevant information to consumers as well as health professionals and other stakeholders. The activities generally focused on informing consumers about the health consequences of high sodium intake and included attempts to motivate consumers to make changes. Efforts to put in place point-of-purchase information about the sodium content of foods and to encourage the food industry to voluntarily reduce the sodium content of foods were included as adjunct activities to assist consumers. Given that sodium intake estimates from national surveys beginning in 1971 have not shown a decline, and suggest that sodium intake has increased, the goal has not been achieved. Despite 40 years of efforts to reduce sodium intake in the United States, intakes remain much higher than recommended levels. The committee first considered the possibility that the failure to reduce intake was due to basic flaws or inadequate implementation of the efforts to educate and motivate consumers. Although it is likely there is room for improvement in these consumer-based initiatives, the explanation appears to rest with the nature of the public health problem itself. In the case of sodium intake reduction, at least two factors limit the success of efforts based on consumer education and motivation alone. Many of the foods consumed by Americans—from breads to entire meals—are processed in ways that include the addition of salt and contribute significant amounts of sodium to the diet. Sodium is relatively ubiquitous in the food supply, and it is challenging for the average consumer to avoid consuming sodium. Americans have become accustomed to high-salt taste preference. When coupled with consumer surveys indicating that taste is a primary influence on food selection and consumption, often overriding other reasons such as health motivations and even cost, this acquired taste preference warrants special attention. Further, because a high-salt diet may actually enhance the liking of salty foods, the U.S. food supply—which is high in added salt—may work against consumers’ successfully lowering their taste preferences for salt and therefore handicap the acceptance of lower-sodium foods. On balance, consumer-based initiatives without a concomitant change in the overall food supply and without considerations related to changing salt taste preference are likely to be inadequate to address the public health problem.
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Strategies to Reduce Sodium Intake in the United States The need for changes in the food supply is not a conclusion unique to this committee, nor are the challenges associated with consuming a low-sodium diet, given the general nature of the food supply as experienced by the average American. Rather, as documented in Chapter 2, the major public health initiatives beginning in 1969 called on the food industry to reduce the sodium content of foods. Table 8-1 lists some examples of related comments from study authors. Despite long-standing efforts by government, public health groups, and food industry leaders to encourage reformulation of foods to lower-sodium content and thus reduce sodium in the food supply, the U.S. food supply remains high in sodium as described in Chapter 2. Between 1984 and 2004, the sodium content of a number of McDonald’s products was reduced by an average of 9 percent; the content of a number of Quaker products was reduced by an average of 23 percent; and the amount of sodium in 13 Campbell’s soup products declined by an average of 10 percent (CSPI, 2005). A tracking survey of a relatively small sample of foods carried out by a public interest group beginning in 1983, indicates that of the 69 products still marketed in 2004, the average sodium content TABLE 8-1 Examples of Comments Concerning the Need for Change in the Food Supply Reference Comment Fodor et al., 2009a “The DASH [Dietary Approaches to Stop Hypertension] diet was successful as long as food was provided to the study participants … as soon as the respondents had to take care of their diet themselves … the beneficial effects of this diet diminished or disappeared.” Kumanyika et al., 2005b “Sodium reduction sufficient to favorably influence the population blood pressure distribution will be difficult to achieve without food supply changes.” Loria et al., 2001 “[In the context] of the overwhelming lack of adherence to dietary sodium guidelines … [there is a] need for a multifaceted approach….” Cleveland et al., 1993c “The results [of the study] document the advantage of a change in the food supply—toward convenience foods with less sodium.” aCopyright © 2009 Journal of Clinical Hypertension. Reproduced with permission from John Wiley & Sons. bReprinted by permission from Macmillan Publishers Ltd: Journal of Human Hypertension 19(1):33–45, Copyright © 2005. cReprinted from Journal of the American Dietetic Association, 93(5), Cleveland et al., Method for identifying differences between existing food intake patterns and patterns that meet nutrition recommendations, pp. 556–560, Copyright © 1993, with permission from Elsevier.
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Strategies to Reduce Sodium Intake in the United States decreased by 5 percent (from 592 to 564 mg) during the 20-year period (CSPI, 2008). However, for the more recent 10-year period (1994–2004), this survey reported an actual increase of 6 percent, suggesting that the reductions gained in the 1980s and early 1990s have been reversed. During the public information-gathering workshop convened by the committee (March 30, 2009), discussions among food industry panelists suggested that a 10–20 percent reduction in sodium for some products was a realistic estimate, but there are also reports that a few products may have achieved a 50 percent reduction in sodium while others achieved reductions smaller than 10 percent.1 While such information is generally encouraging, the overall picture for the United States reveals little success for the industry as a whole. Even though there is evidence of efforts to reduce sodium in some food products on the part of larger food processors and a few restaurant chains, meaningful overall reductions in the food supply have not been accomplished. Specifically, Figure 2-4A indicates, on the basis of sodium density, that the amount of sodium in the overall food supply has not declined over time. Past voluntary efforts by the processed food and restaurant/foodservice industries to reduce the sodium content of the food supply have not been successful in meeting the goal of reducing population sodium intake. Specific reasons cannot be documented but are likely due to a myriad of reasons. A Unilever press release stated that consumers will be more likely to adapt their taste preference to lower levels of salt if the food industry as a whole reduces salt levels.2 During the committee’s public information-gathering workshop (March 30, 2009), a panel of food industry representatives discussed the issue of reducing the sodium content of the foods they sell. One representative stated: We also need to have a much more cohesive industry-wide approach. We have seen, to our detriment when we’ve tried to take a leadership role in reducing nutrients of concern unilaterally in different product areas that the consumers just move to different brands that have higher levels of those nutrients of concern at the expense of our products. And so, unless there is a consistent approach across the industry, with a baseline set so that we’re all operating off a similar starting point, it will be difficult for any one company to take the lead. 1 Personal communication, J. Ruff, Kraft Foods (retired), October 2009. 2 Available online: http://www.unilever.com/mediacentre/pressreleases/2009/Unilevermakesacommitmenttoreducesaltacrossitsportfolio.aspx (accessed November 14, 2009).
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Strategies to Reduce Sodium Intake in the United States This comment is consistent with the Food and Drug Administration (FDA) action to suspend the planned decrease in the levels of sodium per serving that a food product must have to bear the claim “healthy” (HHS/FDA, 2005). In sum, food industry representatives report challenges associated with marketing products with substantially lower sodium—and hence a less acceptable taste profile—compared to competitors’ products. It is known that food taste is an important determinant of food choice, and to alter salt taste preferences will likely require a level playing field approach in which salt reductions are made across the food supply. Luft et al. (1997) offered the following observation: The food industry has made a genuine effort to introduce low-salt food products; however, the public has not been willing to purchase the products and many have been withdrawn because they could not be sold (C.S. Khoo, personal communication, 1994). Pietinen et al. (1984) also observed that during their intervention (in Finland), low-salt bread, margarine, sausage, and mineral water were available. However, by the end of the study, only the mineral water and the margarine were selling well and were still available. Thus, the conclusion that compliance to a low-salt diet is difficult solely because of an uncooperative and nefarious food industry is overstated and not supported by the evidence. Public tastes continue to dictate the marketplace. Given the need for food products to be “palatably competitive,” the food industry lacks a level playing field for reduction of sodium in foods. In view of these findings, the evidence presented in Chapter 3 regarding salt taste provides a foundation for identifying strategies to reduce sodium intake. An important consideration is that while the preference for salt taste, if not addressed, will be a barrier to success in lowering the sodium content of the food supply, salt taste preference is mutable and can be lowered. The preference for salt beyond physiological need may be due to evolutionary pressures to consume salt that have shaped an innate liking for its taste, or, alternatively and perhaps concomitantly, be due to learning, particularly early learning. Continued exposure to high levels of salt in the food supply likely reinforces the preference for a higher level of intake. Kumanyika (1991) noted that the environment promotes adaptation to a higher salt preference, even for individuals who prefer a low sodium dietary pattern, because it is difficult for them to sustain avoidance of inadvertent consumption of foods with high amounts of added salt. Existing experience with lowering the taste preference for salt (Engstrom
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Strategies to Reduce Sodium Intake in the United States et al., 1997; NHLBI, 1996; public information-gathering session held by the committee on March 30, 2009), when coupled with a number of published experimental studies (see Chapter 3), suggest that salt taste preference may be most successfully decreased through a stepwise process and is likely dependent on lowering salt sources overall. The general preference for salt taste can be changed. High levels of salt in the food supply can reinforce the preference for salt taste. Finally, point-of-purchase information about the sodium content of foods has been the third prong of national public health initiatives. Nutrition labels have appeared on packaged foods since the 1970s and were mandated in 1993, but sodium intake has not declined. However, the availability of nutrition information for foods is a prerequisite for consumers’ ability to make informed choices. Availability to consumers of food label information about the sodium content of foods has not been accompanied by an overall reduction of sodium intake by the U.S. population. Regarding point-of-purchase information—health claims or claims about sodium reduction in foods—intended to stimulate the food industry to reformulate foods, the promise associated with the marketability of such claims has not been realized. The ability to make claims about reduced levels of sodium in food products has not stimulated substantial or successful food reformulation or impacted the overall content of sodium in the food supply. Not surprisingly, the label surveys described in Chapter 2 revealed that claims about the sodium content of packaged foods are not widely used. As described in Chapter 6, the food industry likely is concerned that consumers associate reduced- or lower-sodium claims with poor-tasting products. Label claims about the sodium content of food have not been widely used by manufacturers, perhaps because of concern that consumers associate such claims with poor-tasting products. In the face of these unsuccessful national initiatives, some state and local authorities have taken on initiatives intended to reduce sodium intake. Much of this activity has centered on making point-of-purchase sodium information for restaurant/foodservice menu items available to consumers
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Strategies to Reduce Sodium Intake in the United States (see Appendix J). At least one current voluntary initiative in the United States addresses the sodium content of the food supply. The National Salt Reduction Initiative (NSRI), described in Appendix G, was developed initially by the New York City Health Department and has expanded into a national collaboration of state public health authorities and organizations. Based on the United Kingdom (UK) Food Standards Agency’s Salt Reduction Campaign (see Appendix C), the NSRI aims to decrease sodium by setting targets that are defined as substantive and achievable and will result in gradual, measurable reductions of sodium content over time. The initiative includes two parallel components, one focusing on processed foods and the second on restaurants and the foodservice industry. The NSRI uses a food category approach to set targets for the sodium content of foods and relies on voluntary compliance on the part of the food industry. A national collaboration of this type may be useful in encouraging the food industry to voluntarily lower the sodium content of its foods, and the reach of such efforts may extend to communities not actively participating in the initiative given the nationwide distribution of many food products. However, such initiatives are challenged by the inability to ensure that there will be compliance and they do not guarantee a level playing field for food producers. Additionally, it is likely that volunteers will drop out as reductions become more challenging over time. Further, these efforts may not be sustainable in the long term because they rely on “bully pulpit” and strong leadership approaches that can be reduced or lose political popularity with changes in state and local government administration. Additionally, other emerging public health concerns may draw focus away from the sodium initiatives. Overall, the committee’s considerations of the public health initiatives of the past 40 years directed toward lowering sodium intake by the U.S. population are outlined in Box 8-1. INFORMATION FROM SODIUM INITIATIVES IN OTHER COUNTRIES Appendix C contains specific information on efforts to reduce sodium intake in the United Kingdom, Canada, Finland, France, and the European Union. Components of these programs are summarized in Table 8-2, and the programs are described below. Of the countries for which information is available, Finland has had the longest experience; initiatives were begun in the 1970s when intake was estimated to be more than 5,000 mg/d for adult males. Stroke mortality and blood pressure rates have declined. The efforts in the United Kingdom, which are relatively comprehensive, are of more recent origin with initia-
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Strategies to Reduce Sodium Intake in the United States BOX 8-1 Findings from Review of Public Health Initiatives The lack of success in reducing sodium intake population-wide in the United States indicates that prior initiatives were not sufficient in the face of the nature of the public health problem they are meant to address. Without an overall reduction in the level of sodium in the food supply—that is, the level of sodium to which consumers are exposed on a daily basis—the current focus on instructing consumers and making available reduced-sodium “niche” products cannot result in lowering intakes to levels consistent with the Dietary Guidelines for Americans. Food industry efforts to voluntarily reduce the sodium content of the food supply face technological challenges, are not consistently undertaken by all, are difficult to sustain on a voluntary basis, and in the aggregate have not resulted in overall success. Food manufacturers and restaurant/foodservice operators face challenges in marketing lower-sodium foods in the context of the current food supply because such foods may be considered less palatable than higher-sodium competitors; it is known that food taste is a major determinant of food choice. What is lacking is a level playing field. A factor germane to improving the success of efforts to reduce sodium intake is that persons have become accustomed to high-salt taste, but the preference can be changed. Since a high-salt diet may actually enhance a preference for salt taste, a food supply with high levels of salt may handicap the acceptance of lower-sodium foods. Reductions in the preference for salt taste are likely best accomplished through gradual, stepwise reductions of sodium across the food supply. tives beginning in 2003, following a national survey in 2000–2001 that suggested an average daily intake of more than 3,800 mg/d of sodium. The activities in Finland focused on extensive media campaigns in the 1970s and 1980s, during which consumer awareness was the focus. These were followed by required labeling in the 1990s. The labeling is targeted to eight food categories known to be rich sources of salt in the diet: bread, sausages, cheese, butter, breakfast cereals, crisp bread, fish products, and soups, sauces, or ready-made dishes. Those foods that exceed a certain level of salt based on the percentage of salt “by fresh weight of the product” are required to bear a “high-salt” label, while those below certain percentages of fresh weight of product are allowed to bear a “low-salt” label. In Finland, manufacturers apparently worked to reduce the sodium content of foods in these eight food categories, achieving for example a 10 percent reduction in the sodium content of sausages. Based on sodium excretion measures, the efforts in Finland coincided with a drop in sodium
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Strategies to Reduce Sodium Intake in the United States TABLE 8-2 Overview of Initiatives in Other Countries Country Public Education Requests to Industry for Sodium Reformulation Food Labeling Comments About Program Canada Yes Yes Voluntary Early voluntary reductions by food industry combined with public education and labeling had no impact on sodium intake from processed foods Too early to assess Finland Yes Yes Mandatory Government regulation and implementation of food labeling with high-sodium-content warning Strong media campaigns to increase public awareness Much sodium intake under control of consumer (salt at table) Replacement of usual salt with potassium-enriched Pansalt Sodium intake decreased from 5,600 mg in 1972 to 3,200 mg in 2002 Blood pressure and stroke mortality rates declined France Yes Yes Voluntary Efforts initiated in 2004 Optional sodium labeling being developed Limited public education in which sodium reduction is the main message; done through the National Nutrition and Health Program Not much change to date except in the bakery sector, where 33% of bakers claim to have reduced sodium Ireland Yes Yes Voluntary pending Collaborative program between government and industry to heighten industry’s awareness about salt and health Government seeks salt reduction commitments from industry sectors; more than 70 have registered Working on voluntary universal labeling of salt in packaged foods No intake data available post-implementation
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Strategies to Reduce Sodium Intake in the United States Country Public Education Requests to Industry for Sodium Reformulation Food Labeling Comments About Program United Kingdom Yes Yes Voluntary Collaborative effort with food industry for targeted sodium reduction in specific groups of foods under the oversight of the Food Standards Agency Ongoing monitoring and evaluation of population intake Public campaigns to increase public awareness and labeling strategy geared toward informing consumers Sodium intake decreased from 3,800 mg in 2004 to 3,440 mg in 2008 SOURCE: Adapted from Mohan et al. Copyright © 2009 Canadian Medical Association. This work is protected by copyright and the making of this copy was with the permission of Access Copyright. Any alteration of its content or further copying in any form whatsoever is strictly prohibited unless otherwise permitted by law. intake between 1979 and 2002 from more than 5,000 mg/d to less than 3,900 mg/d among men and from nearly 4,000 mg/d to slightly less than 3,000 mg/d for women (Laatikainen et al., 2006). However, use of salt added at home has been notably higher in Finland than in the United States, and the majority of the reported reduction in sodium intake was primarily due to a reduction of almost 50 percent in salt added by consumers at the table or in the home. More specifically, in 1980, the average Finnish sodium intake was 5,080 mg/d, of which 30 percent was from table salt used in households. This is compared to 1997–1999 when the average intake was 4,440 mg/d, of which 21 percent was from table salt used in households. Thus, in 1980, approximately 1,520 mg/d of sodium was added by the consumer and 3,560 mg/d came from other sources, compared to 1997–1999 when approximately 930 mg/d of sodium was added by the consumer and 3,510 mg/d came from other sources (Reinivuo et al., 2006). The UK effort at present is an entirely voluntary activity that relies on the impact of strong messaging from public health authorities, highly targeted and specific messages to the population, and highly visible efforts to enlist industry involvement and cooperation. These activities have been the focus of considerable government activity ranging from dialoguing with stakeholders to set appropriate and workable targets for reducing the
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Strategies to Reduce Sodium Intake in the United States salt content of key food categories to efforts to track progress toward the goal to government-sponsored awareness campaigns. Further, supermarkets and manufacturers are requested to voluntarily display front-of-package labeling of sodium and other nutrients using a traffic light color system. While a review of progress and the salt targets is planned for 2011,3 the UK government reported reductions in sodium intake among the general population from an average of 3,800 mg/d in 2000–2001 to 3,440 mg/d in 2008 based on urine analysis of approximately 700 adults (National Centre for Social Research, 2008). The latter estimate is in line with the current U.S. dietary estimates. The 2011 review is planned to include information about the costs of the program. In 2007, the Canadian government launched a multistakeholder working group on sodium reduction. The group intends to work in stages and should shortly be issuing a strategic framework that is slated for implementation in 2010. In 2003, Ireland began its work with a program intended to raise the food industry’s awareness about the relationship between salt and health, and to work with the industry to voluntarily reduce sodium levels in foods. The Irish government reports that 72 companies have registered with the program, and reductions of approximately 20 percent in the sodium content of key foods such as breads and sausages have been reported. Similar to the situation in the United Kingdom, Irish intake estimates for sodium have been reported to be higher than U.S. estimates, but no recent national estimates subsequent to the implementation of the program are available. The French government released a report in 2002 that recommended a 20 percent reduction in sodium intake for its population and developed initiatives for consumers, the food/catering industry, and medical professions. To date, no significant changes have been reported in the salt content of processed foods or in the level of food labeling incorporated. Finally, the European Union has developed a so-called common framework approach to reducing salt intake among the populations of its member countries. The framework will focus on 12 categories of food identified as priorities. No information on the cost effectiveness of these international strategies could be gleaned from the available data, although the United Kingdom plans to release information about the cost of its program in 2011. Clearly, reducing sodium intake is a public health priority beyond the United States. The ability to directly relate existing reports from other countries to strategies that would be workable in the United States is somewhat difficult, given differences in food patterns, regulatory provisions, government resource capabilities, and consumers’ perspectives on the food supply as well as the perceived importance of reducing sodium intake. In particular, 3 Available online: http://www.food.gov.uk/healthiereating/salt/saltreduction (accessed November 16, 2009).
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Strategies to Reduce Sodium Intake in the United States wise, systems to monitor and evaluate the impact of such programs closely over time help to track the possibility of such consequences and identify those that emerge in unexpected ways. The section identifies four unintended consequences that are potentially associated with the implementation of strategies to reduce sodium intake. Awareness of such consequences among the medical and public health communities will be essential for ensuring that any such adverse events are quickly identified and mitigated. Adverse Effects of Low Sodium Intake Concerns have been raised that low sodium intake adversely affects plasma renin activity, sympathetic nervous system activity, blood lipids, and insulin resistance. The suggestion is that attempts to achieve the levels recommended in the Dietary Guidelines for Americans on a population basis would place some persons at risk. When sodium intake is reduced, there is a physiological stimulation of counter regulatory hormone systems, specifically the renin-angiotensin system and the sympathetic nervous system (IOM, 2005). These compensatory responses are much greater with abrupt large changes in sodium intake than with gradual reductions (Sagnella et al., 1990) as currently recommended. Furthermore, in contrast to the well-accepted benefits of blood pressure reduction, the clinical relevance of modest rises in plasma renin activity as a result of sodium reduction is uncertain. Other studies have examined the effects of changing sodium intake on lipids, glucose tolerance, and insulin sensitivity. Adverse changes have been noted in some studies, but these studies often involved a very large change in sodium intake for only a few days. In the largest and longest controlled trial that addressed the effects of sodium reduction on blood lipids, there was no significant effect of sodium levels within the recommended range of intake (Harsha et al., 2004). Accordingly, the IOM, as part of its Dietary Reference Intake development process for nutrients including sodium, concluded that at the level of intake consistent with the reference value, the preponderance of evidence does not support the contention that the recommended intake would adversely affect any of these measures (IOM, 2005). Food Safety Because salt and other sodium-containing compounds function as food preservatives, efforts to reduce their presence have the potential to impact the safety of the food supply. Past efforts to reformulate foods to improve their nutrient composition have occasionally resulted in foodborne illness. A well-known example is an effort to make sugar-free hazelnut conserve for use in reduced-calorie
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Strategies to Reduce Sodium Intake in the United States yogurt products in the United Kingdom (Entis, 2007). The conserve maker substituted aspartame for sugar without altering the rest of the formulation and without altering processing. The sugar present in the original formulation prevented the growth of Clostridium botulinum, but with its removal, this organism was able to grow and eventually led to the death of 1 person and serious illness in 25 others. This event is an example of the unfortunate outcomes that are possible if the safety-related functions of ingredients are not considered during reformulation. However, such events are preventable with adequate food safety expertise and product testing. Consistent with FDA authorities and mission, the proposed changes to the status of GRAS substances must be demonstrated to be safe before they can be incorporated into regulation and implemented. To avoid problems from occurring during sodium reduction, food companies generally evaluate the potential for reduced sodium levels to increase food safety risks and engineer additional hurdles to microbial threats (as described in Chapter 4) into the product. In addition, it is generally standard practice to validate the safety of new and reformulated products using shelf life testing. The results of these tests will determine the limits of sodium reduction for specific food products and provide information that can be used to educate the standard setting process for acceptable conditions of use. Such testing, for example, may help to determine the potential for the growth of Listeria monocytogenes—an organism that has raised food safety concerns during UK efforts to reduce salt—in reduced-sodium deli meats or cheeses (Advisory Committee on the Microbiological Safety of Food ad hoc Group on Vulnerable Groups, 2008). Such testing is time consuming, requiring that adequate phase-in periods be provided to ensure that the push for a lower-sodium food supply does not result in unintended food safety problems. Smaller companies may not have as great a capacity to quickly undertake the studies needed to ensure the safety of reformulated foods and may need more time to meet sodium reduction goals than larger companies with significant resources for research and development. Specialized guidance from FDA, trade associations, and the Cooperative Extension service may also help to fill knowledge gaps in companies with limited research and development staffs. With sufficient guidance, standards for conditions of use that recognize food safety limitations, and the regular practice of validating product safety with shelf life testing, most food safety concerns should be avoidable. Iodine Insufficiency Until the 1920s, endemic iodine deficiency was a major public health problem in the Great Lakes, Appalachian, and Northwestern regions of the United States (Pearce, 2007). The introduction of iodized salt on a volun-
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Strategies to Reduce Sodium Intake in the United States tary basis by manufacturers and extensive public education programs by health officials to encourage consumer use of this product resulted in the virtual elimination of goiter in high-risk regions. The question then arises as to whether strategies to reduce salt intake by the U.S. population will result in the unintended consequence of increasing the risk of iodine insufficiency and deficiency among high-risk groups. To answer this question, it is important to determine the current iodine status of the U.S. population and to anticipate the potential effect of reduced salt intake on iodine status. However, assessing the iodine status of the U.S. population is challenging. Intake data are generally unreliable because they cannot accurately estimate the amount of table salt used by consumers, and information about whether iodized or non-iodized salt is used in food preparation at home or away from home is rarely captured in food composition databases or in dietary interviews. There are wide variations in the iodine content of some common foods. For example, the iodine content per slice of bread was > 300 μg for three varieties of bread and averaged 10 μg for 17 other brands in 2002 (Pearce, 2007), thus making it difficult to assign meaningful composition values to specific food items. The labeling of the iodine content of foods is not mandatory unless claims are made or iodine is added as a nutrient fortificant—practices that to date have been rare. On the other hand, dietary supplements, particularly multivitamin and multimineral supplements, often contain 150 μg of iodine per daily dose and the iodine content of these products is declared on the label. Because of the difficulty of obtaining accurate estimates of dietary intake, iodine status is generally assessed by urinary excretion of iodine. Iodine is renally excreted, therefore urinary iodine concentrations are an indication of dietary iodine sufficiency (Pearce, 2007). The National Health and Nutrition Examination Surveys (NHANES) have periodically collected casual urine samples from which iodine values have been determined since NHANES I was conducted from 1971–1974. These data have been used to examine trends in urinary iodine excretion over time (Caldwell et al., 2005). NHANES I levels were considered to be “adequate to excessive” for iodine (Pearce, 2007). Then, a downward trend was noted in urinary iodine concentration between NHANES I (320 ± 6 μg/L in 1971–1974) and NHANES III (145 ± 3 μg/L in 1988–1994). However, NHANES 2001–2002 data indicate that the urinary excretion of iodine stabi2lized (167.8 μg/L; 95 percent confidence interval: 159.3–177.6 μg/L). NHANES III and NHANES 2001–2002 urinary iodine excretion concentrations are within the range generally considered to be “optimal” for iodine nutriture (Caldwell et al., 2005; Pearce, 2007). The reasons for the reductions in urinary iodine concentration between
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Strategies to Reduce Sodium Intake in the United States 1971–1974 and 1988–1994 cannot be determined precisely, but they appear to be a function of a food industry response to concerns expressed by FDA that manufacturing practices were causing excessive levels of iodine in the food supply. That is, the reduction may have been due to efforts to reduce iodine in the food supply from a potentially toxic level to a more acceptable level of nutriture for the general population. In the 1970s, chemical analysis of an FDA market basket sample of foods representative of U.S. dietary patterns showed extremely high and increasing levels of iodine in dairy products, grain and cereal products, and meat, fish, and poultry (Park et al., 1981). Sugars and adjunct groups (e.g., pudding mixes, jam, jelly, candies) also contained substantial amounts of iodine. Although the sources of iodine in these foods were not definitely determined, they are likely to have been iodophors used at that time as cleaning agents in dairy production, high levels of iodine added to animal feed, use of red color dyes containing iodine, and iodates used as baking conditioners in the making of breads (Pearce, 2007). FDA shared its concerns about these findings with the food industry (Park et al., 1981). The iodine content of the food supply subsequently dropped. The current iodine status of the U.S. population is within an adequate range according to generally accepted guidelines for assessing iodine nutriture—although some groups (e.g., pregnant women) may be at higher risk than the general population (Caldwell et al., 2005; Pearce, 2007). Given current levels of iodine intake, what is likely to happen if salt reduction strategies were to be implemented? This is addressed by considering the contribution of iodized salt to total intake of iodine. Currently, the main use of iodized salt is for home table salt—of which about 70 percent of sales are for iodized salt (Pearce, 2007). Non-iodized salt is used in most food processing and restaurant/foodservice applications (Dasgupta, 2008). Current intake data show that only about 5 percent of sodium comes from the use of table salt (see Chapter 5). Much of the iodine in today’s diets continues to come from non-salt sources (e.g., iodine-containing food additives, processing aids, foods grown in many regions and countries) (IOM, 2005)—sources that would not be affected by salt reduction. Therefore, if 5 percent of sodium in today’s diet is assumed to be associated with iodized salt and the major sodium reduction strategies in this report are addressed to the sodium content of processed and restaurant/foodservice foods, it would appear that the recommended sodium reduction strategies would have minimal impact on iodine intake of the U.S. population. Nonetheless, as a matter of public health prudence, continued and improved monitoring of urinary iodine excretion of the U.S. population and chemical analysis of the iodine content of market basket foods representative of U.S. dietary patterns are warranted.
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Strategies to Reduce Sodium Intake in the United States Potassium in the Food Supply Due to Use of Potassium Chloride as a Salt Substitute Potassium chloride is used as a salt substitute, and efforts to reduce sodium intake likely will incorporate more uses of potassium chloride as a salt substitute in food. In fact, an IOM committee recently recommended that CDC consider, as a strategy for preventing and controlling hypertension in the U.S. population, advocating for the greater use of potassium/sodium chloride combinations as a means of simultaneously reducing sodium intake and increasing potassium intake (IOM, 2010). While dietary guidance generally encourages increased intake of potassium (DGAC, 2005), this recommendation is in the context of healthy populations, most of whom would benefit from additional potassium in the diet. However, there may be unintended consequences for a sizable subpopulation in the United States if potassium chloride is used widely and at high levels, especially since the potassium content of foods is not generally provided in label information. Adverse cardiac effects (arrhythmias) can result from hyperkalemia, which is a markedly elevated serum level of potassium. In individuals whose urinary potassium excretion is impaired by a medical condition, drug therapy, or both, instances of life-threatening hyperkalemia have been reported (IOM, 2005). There have been several case reports of hyperkalemia in individuals who reported use of a potassium-containing salt substitute while under treatment for chronic diseases (Haddad, 1978; Ray et al., 1999; Snyder et al., 1975). Many Americans are taking medications that result in an increase in serum potassium. Angiotensin-converting enzyme (ACE) inhibitors, angiotensin receptor blockers (ARBs), and potassium-sparing diuretics are common drugs that can significantly reduce potassium excretion (DGAC, 2005). Medical conditions associated with impaired potassium excretion include diabetes, chronic kidney disease, end-stage renal disease, severe heart failure, and adrenal insufficiency. Individuals with these conditions are numerous in the U.S. population. For the approximately 26 million Americans with chronic kidney disease (Lloyd-Jones et al., 2009), these increased serum levels may be exacerbated by widespread potassium chloride use. There may also be concern relative to people with hypertension using ACE inhibitors and ARBs, which are commonly prescribed and have been shown to cause hyperkalemia (defined in the study as serum potassium concentration > 5.5 mEq/L or mmol/L) in approximately 3.3 percent of those taking them (Yusuf et al., 2008). These drugs are also used in patients with diabetes who have microalbuminuria or frank proteinuria to decrease urinary protein excretion and protect their renal function.
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Strategies to Reduce Sodium Intake in the United States There are approximately 5 million Americans with congestive heart failure,14 and a mainstay of their treatment is spironolactone, which blocks the hormone aldosterone and is associated with hyperkalemia. Indeed, a study from Canada showed that shortly after a publication reported a positive effect of spironolactone use in patients with congestive heart failure, its use increased markedly and resulted in a more than 400 percent increase in hospitalizations due to hyperkalemia, and mortality rose from 0.3 per 1,000 to 2.0 per 1,000 patients (Juurlink et al., 2004). The number of Americans potentially at risk for adverse effects from potassium intake warrants vigilance in the increased use of potassium chloride as a salt substitute. Systematic monitoring of the food supply is essential for tracking the use of potassium chloride in foods and to monitor, and in turn mitigate, its ability to cause adverse health effects in those at risk. MONITORING The need for monitoring and surveillance is critical to establishing baseline data for and tracking the progress of strategies to reduce sodium intake. Both data on population intake and data on sodium levels in the food supply are needed to provide an information base for implementation of the recommended strategies. More accurate assessment and tracking of (1) specific foods that are contributors to Americans’ sodium intake and (2) population-level dietary sodium intake, including the monitoring of 24-hour urinary sodium, were recently recommended by an IOM committee charged with reviewing public health strategies for reducing and controlling hypertension in the U.S. population (IOM, 2010). To date, monitoring efforts have been basic and focused on estimating intake from dietary self-reports collected as part of national surveys. Systematic and relevant approaches to tracking the sodium content of the food supply are lacking. Furthermore, useful and informative surveys conducted at the national level—such as the Total Diet Study and the Food Label and Package Survey—have not been conducted systematically, have failed to release data in timely and useful formats, and do not include sufficient coverage of sodium-related measurements. Although available food composition databases, which are essential to formulating sodium intake estimates based on dietary recall methods, have improved over the years, there is still room for more comprehensive data collection and reporting, especially in the area of restaurant foods. Importantly, a more accurate measure of total sodium intake such as 24-hour urine collection should be employed in national population surveys, specifically NHANES. Dietary estimation must continue because it 14 Available online: http://www.nlm.nih.gov/medlineplus/heartfailure.html (accessed November 16, 2009).
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Strategies to Reduce Sodium Intake in the United States is important for identifying dietary patterns and use of foods relevant to increased or decreased sodium intake, but urinary analysis is required for the increased precision needed now for sodium monitoring and surveillance (see Recommendation 5). It is desirable to explore new approaches for monitoring the sodium content of the food supply. One possibility that could provide detailed sodium content information and trends by individual product and by processed food category, including by sales weight, would be to link Universal Product Code (UPC) sales data to information on the nutrient content of the food as stated on the Nutrition Fact panel. Such a method is currently being used by the NSRI spearheaded by the New York City Health Department. Although such data are limited because they cannot provide information on the amounts of foods consumed or how foods were ultimately prepared and are subject to errors due to the inability to match some UPC codes with nutrient data, they could be a useful snapshot of trends. An approach to developing such a system is described in Appendix K. Further, efforts to appropriately expand or find an alternative to the FDA’s Total Diet Study are worthwhile. On a related note, monitoring the use of claims about sodium is important. Efforts to ensure the continuation of FDA’s Food Label and Package Survey and the expansion of this survey to encompass tasks important to monitoring strategies for reducing sodium intake should be made (see Recommendation 5). New and enhanced methods to help consumers self-monitor their sodium intake would be useful in supporting consumer behaviors. Options that would advance the development of such methods include: enhancing currently available tools, such as dietary estimations through the MyPyramid online program; creating new mechanisms for monitoring dietary intake, such as mobile software for tracking individual sodium intake; and exploring kits that could be used for home urine testing to estimate individual intake. Moreover, monitoring of consumers’ knowledge, attitudes, and food selection practices along with the use of food labeling is needed to enhance the picture of factors important to realizing meaningful reductions in sodium intake. Several national surveys have such components, and these could be enhanced and expanded as they relate to sodium intake. Additionally, methods to monitor salt taste preference need attention and, when developed, should become part of the national monitoring system (see Recommendation 5). Finally, it is always in the best interests of public health when major initiatives such as a population-wide effort to reduce sodium intake are undertaken to ensure that there is monitoring relative to unintended consequences. These range from the careful monitoring that would be needed for the successful stepwise reduction of sodium in the food supply and its
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