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Strategies to Reduce Sodium Intake in the United States 2 Sodium Intake Reduction: An Important But Elusive Public Health Goal For 40 years, the numerous public health initiatives to reduce sodium intake of the U.S. population focused on consumer education and behavior change. These activities were accompanied by requests to the food industry (defined as both the processing and restaurant/foodservice sectors) to assist consumers by marketing lower-sodium alternatives and voluntarily reducing the amount of sodium in its foods, as well as requests to provide information on the sodium content of foods at the point of purchase. Efforts to provide such point-of-purchase information relate to both the consumer-oriented strategies and the supporting strategies associated with voluntary changes in the food supply. That is, nutrition labeling—which includes information about sodium—is intended to assist consumers at the point of purchase; the ability to make claims on food labels about the sodium content of the product was historically viewed as providing an incentive to the processed food industry to voluntarily reformulate its food products, while at the same time informing consumers at the point of purchase. This chapter highlights these past and current U.S. initiatives and considers whether the intended outcome of reducing the sodium intake of Americans has been achieved. More information about the data presented in this chapter as well as other factors important to strategies for reducing sodium intake can be found in the background chapters that appear later in this report. In addition, Appendix C provides a summary of past and current efforts to reduce sodium intake internationally.
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Strategies to Reduce Sodium Intake in the United States PAST RECOMMENDATIONS AND MAJOR INITIATIVES Initiatives The 1969 White House Conference on Food, Nutrition, and Health is often regarded as the starting point for national initiatives to reduce sodium intake. Beginning in 1969 and continuing through the present time, numerous initiatives have been developed by a myriad of government public health agencies (FDA, 1975–2007; HHS, 1979–2000; NHLBI, 1972–2006; Senate, 1977; state and local agencies, 2008–2009; USDA, 1993–2008; USDA/HHS, 1980–2005; White House, 1969); independent national and international authoritative scientific bodies (NRC/IOM, 1970–2010; WHO, 1990–2003); and health professional organizations (ADA, 2007; AHA, 1973–2008; AMA, 1979–2006; APHA, 2002). These initiatives have ranged in scope from sweeping national dietary recommendations and goal-setting activities to fact sheets for consumers and health professionals, to calls for food industry and government actions to create or alter policies that might help to reduce sodium intake. When combined, these various initiatives have played a role in attempting to reduce the sodium intake of Americans. Too numerous to describe in detail, these efforts are listed in Table 2-1 and summarized in Appendix B. Many of these initiatives were developed as part of a public process that involved scientists, consumers, and members of the food industry. Their existence demonstrates the level of resources and effort that have been mustered to reach the goal of lowering sodium intake. Many of these activities disseminated relevant information to consumers directly as well as to the food industry and to “multipliers” such as health professionals and the media. Some of the messages about sodium were linked to other public health messages and campaigns focusing on dietary factors (e.g., increased consumption of fruits and vegetables, decreased saturated fat intake) and chronic diseases and other health conditions with diet-related risk factors (e.g., heart and other cardiovascular diseases, obesity and overweight, cancer, diabetes, osteoporosis, bone health). The food industry and consumer advocacy groups also provided consumer information on the topic. At the federal level, the National Heart, Lung, and Blood Institute (NHLBI) within the National Institutes of Health has served as a federal leader in the area of dietary sodium reduction by providing a number of enabling tools for dietary change related to sodium intake. Early efforts included sponsorship of the National High Blood Pressure Education Program (NHBPEP). This was a cooperative effort involving professional and voluntary health agencies, state health departments, and community groups with the goal of reducing death and disability related to high blood
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Strategies to Reduce Sodium Intake in the United States pressure through programs of professional, patient, and public education. The NHBPEP published scientific reviews and recommendations in 1972, 1993, and 1995 and cosponsored a large national public information-gathering workshop in 1994 with other federal agencies (NHLBI, 1996). Auxiliary activities of the NHBPEP included the production of fact sheets, pamphlets, and brochures dealing with lifestyle changes, planning kits, posters and print ads, radio messages, and working group reports. More recently, scientific reviews, recommendations about sodium reduction, and auxiliary outreach activities have been part of the 1997 and 2003 activities of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure. Partnerships with state, local, and community-based organizations formed the basis for the recent development and dissemination of educational materials and the production of broadcast-ready public service announcements about fighting high blood pressure through dietary changes. Initiated in 1980 by congressional mandate, the Dietary Guidelines for Americans provide science-based guidance to promote health and reduce risk for major chronic diseases through diet and physical activity. The U.S. Department of Agriculture (USDA) and U.S. Department of Health and Human Services (HHS) jointly sponsor the development of Dietary Guidelines for Americans, including the convening of an expert advisory committee. The recommendations are regularly revised and updated on a 5-year cycle; to date, six editions of the Dietary Guidelines for Americans have been published. Currently, an expert advisory committee is reviewing the science in preparation for the seventh edition. Since the document was first published in 1980, every edition has contained recommendations for Americans related to reduction in and moderation of sodium intake, but quantitative recommendations were not included until the 2005 edition. To assist consumers in implementing the Dietary Guidelines for Americans through informed food choices, USDA developed the MyPyramid program,1 which is one of its major consumer initiatives for dietary change. Implementation of the sodium recommendations as an area of focus was particularly challenging. To help consumers meet recommendations from the Dietary Guidelines for Americans, USDA provides a menu planning program on its website2 that allows individuals to enter information about the foods they consume and to compare their daily food intake with Dietary Guidelines for Americans recommendations. However, sodium as an area of focus is not included. That is, sodium levels are not factored into the MyPyramid 1 Available online: http://www.mypyramid.gov (accessed November 16, 2009). 2 Available online: http://www.mypyramidtracker.gov/planner/ (accessed November 16, 2009).
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Strategies to Reduce Sodium Intake in the United States TABLE 2-1 Summary of Public Health Recommendations, Initiatives, and Actions That Address Sodium Intake in the United States, 1969–Present
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Strategies to Reduce Sodium Intake in the United States
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Strategies to Reduce Sodium Intake in the United States Plan or the MyPyramid Menu Planner tools. There is a footnote3 in the MyPyramid Menu Planner explaining that sodium cannot be accurately calculated using the tool because sodium levels can vary so much within a single food and it is difficult to estimate consumers’ discretionary salt use. Further, in 1995 USDA initiated sodium standards for 10 commodity food categories in its Commodity Distribution Program targeted to school meals (USDA, 1995). Starting in 2004, it implemented sodium reduction efforts into the HealthierUS School Challenge4 and the Special Supplemental Nutrition Program for Women, Infants, and Children programs (USDA/FNS, 2007). In parallel with federal efforts aimed at sodium reduction strategies, efforts by professional and health associations to develop and disseminate information about organization goals and recommendations have also been used to create awareness. Sodium reduction initiatives were started by the American Heart Association in 1973 and the American Medical Association in 1979 and have continued to the present. Their recommendations urge the public to aim for lower sodium intake (Havas et al., 2007; Lichtenstein et al., 2006). Other groups such as the American Public Health Association and the American Dietetic Association have also been active in promoting sodium reduction messages. Many government-based initiatives have called on the industry and other stakeholders to assist consumers in reducing their sodium intake. Consumer advocacy groups, such as the Center for Science in the Public Interest (CSPI), have spread the message of the importance of reducing salt in the diet. Further, online health information sites are accessible sources of health information for many Americans. The food industry has included information on sodium and health on its websites. For example, Campbell’s5 and Kellogg’s6 have information on healthy sodium intake on their websites, and General Mills is a partner in sponsoring the Eat Better America website, which contains sodium and health information.7 3 Available online: http://www.mypyramidtracker.gov/planner/planner_salt.html (accessed November 16, 2009). 4 Available online: http://www.fns.usda.gov/TN/HealthierUS/all_chart.pdf (accessed November 16, 2009). 5 Available online: http://www.campbellwellness.com/subcategory.aspx?subcatid=3 (accessed November 16, 2009). 6 Available online: http://www.kelloggsnutrition.com/know-nutrition/sodium.html (accessed November 16, 2009). 7 Available online: http://www.eatbetteramerica.com/diet-nutrition/heart-health/try-a-sodium-shake-down.aspx (accessed November 16, 2009).
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Strategies to Reduce Sodium Intake in the United States Core Message to Consumers The basic message to consumers about the role of sodium in the development of elevated blood pressure has not changed during the past 40 years, but changes in the target audience as well as the approach to reducing sodium intake have evolved as the science has matured. Many of the early messages and nutrition labeling initiatives focused on persons with diagnosed high blood pressure and those at high risk for high blood pressure or both (Loria et al., 2001), as well as elderly people. As new science emerged, the focus expanded to include all adults as well as children. The extended focus for adults was based on evidence suggesting that generally reducing sodium intake could prevent or minimize age-related increases in blood pressure. The inclusion of children (2 or more years of age) was based on concerns about the development of preferences for salt taste at young ages and the increasingly earlier development of high blood pressure in adolescents and young adults (DGAC, 2005). Further, messages for at-risk subgroups within the general population (e.g., persons with hypertension, African Americans, and middle-aged and older persons) continue to be provided because of the higher incidence rates and more serious consequences of excessive sodium intake for these subgroups (DGAC, 2005). These separate messages are based on the understanding that these at-risk subgroups benefit from a more stringent sodium reduction than that recommended for the general population. Although, as discussed in Chapter 1, the expansion of recommendations to the general population has engendered considerable controversy from some stakeholders (Alderman, 2010; Cohen et al., 2006; Loria et al., 2001; McCarron, 2000, 2008; McCarron et al., 2009), the many expert advisory panels used in the development of sodium reduction recommendations and guidelines, including both those convened by government agencies and those convened independently, have consistently and repeatedly concluded, after careful evaluation of the available scientific evidence and stakeholder concerns, that the scientific evidence warrants extending recommendations for reduction of sodium intake to the general population and across the lifespan. Over the years, the message content also changed from advice for consumers to reduce the addition of salt added to foods at the table or in home food preparation to choosing high-sodium foods in moderation and using the nutrition label when purchasing foods to enable selection of foods with lower sodium content (Loria et al., 2001). This change was based on evidence showing that the major sources of sodium in the U.S. diet were processed foods and foods obtained from restaurant/foodservice operations rather than from salt added by consumers during home food preparation or at the table.
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Strategies to Reduce Sodium Intake in the United States Past Recommendations for Food Industry Actions and Point-of-Purchase Information Many of the initiatives identified in Table 2-1 include recommendations that food processors voluntarily reduce the sodium content of their foods, market lower-sodium alternatives, and make information on the sodium content of their foods readily available at the point of purchase. More recently, calls have also been made for restaurants and other foodservice operations to do the same. These earlier efforts focusing on the food industry were supported and heightened by the results from a small but frequently cited study published in 1991 (Mattes and Donnelly, 1991). It found that processing-added sodium provided more than 75 percent of the total sodium intake of individuals. Another 5 percent was attributable to salt added during cooking and 6 percent was due to salt added by consumers at the table. Subjects had control over the amount of salt added during cooking; during the 7-day study period they ate fewer than three meals away from home and prepared their own meals at home. Thus, the amount of sodium directly under the control of the individual was shown to be relatively small, and most dietary sodium was shown to come from sources beyond consumers’ direct control. Consistent with this, Engstrom et al. (1997) reported that even with a 65 percent reduction in discretionary salt use (i.e., from 1,376 mg/d sodium in 1980–1982 to 476 mg/d in 1990–1992), average daily sodium intake remained > 3,000 mg/d—a level in excess of the Dietary Guidelines for Americans goal of < 2,300 mg/d. As mentioned previously, these data put in motion a change in the emphasis of recommendations from encouraging consumers to reduce or avoid salt use at the table and in home food preparation to an emphasis on encouraging food processors to reduce the sodium content of their products. Calls for point-of-purchase information about the sodium content of foods increased. When the 1990 Nutrition Labeling and Education Act (NLEA) was enacted, the Food and Drug Administration (FDA) ensured that sodium was one of the nutrients that must be declared on the labels of processed foods. At the same time that requests were being made to members of the food industry to voluntarily reduce sodium in their products to assist consumers in lowering their sodium intake, concerns were being raised about the safe use of salt in foods, specifically the levels of salt added by manufacturers. An independent expert panel evaluating this topic in 1979 (SCOGS, 1979) recommended, among other things, that FDA develop guidelines for the safe use of salt in processed foods. As described in more detail in Chapter 7, FDA deferred action on these recommendations, suggesting that the largely voluntary 1975 sodium-based nutrition labeling regulations coupled with
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Strategies to Reduce Sodium Intake in the United States newer 1982 regulations specifically targeting sodium information on food products would likely be effective in helping consumers reduce their sodium intake and stimulating voluntary reductions by manufacturers of sodium in labeled foods (HHS/FDA, 1982). Later, in implementing the 1993 nutrition labeling regulations, FDA and others anticipated that the regulations relating to mandatory declaration of the sodium content of foods and sodium-related criteria for voluntary food label claims (described in Chapter 7) would further aid consumers in selecting lower-sodium foods and stimulate manufacturers to reduce the sodium content of marketed foods. However, despite these significant increases in labeling requirements and opportunities, sodium intake remained high. Concerns that FDA may still need to address the levels of salt added to foods resurfaced with a 2005 citizens’ petition (CSPI, 2005a) and language in a congressional appropriations bill requesting that FDA take action in reviewing the regulatory options for salt added to foods. FDA held public hearings in 2007 to gather information relevant to a possible reexamination of the regulatory status of salt (HHS/FDA, 2007). OUTCOMES To assess whether public health initiatives over the past 40 years were associated with relevant changes, four major areas were examined: (1) consumer awareness and behaviors, (2) sodium levels in the food supply, (3) sodium intake, and (4) prevalence of hypertension. The data sources for the collation of this information were primarily published survey results from the national nutrition monitoring system. Some of these areas are described in more detail in other sections of this report. Consumer Awareness and Behaviors A common theme running through the myriad initiatives and programs described in Table 2-1 and Appendix B is that providing advice to consumers on the health risks associated with high sodium intake would result in increased consumer awareness and would motivate consumers to take action to reduce their sodium intake. It was also anticipated that providing consumers with information about the sodium content of processed and restaurant foods at the point of purchase would help them select lower-sodium foods and, thus, reduce total intake. The question then arises: How successful have the many initiatives carried out over the past four decades been in achieving these goals? Although the available evidence is limited, it does provide insights into the success, or lack thereof, of consumer education and information initiatives. This section reviews available information on consumer understanding
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Strategies to Reduce Sodium Intake in the United States and behavior related to sodium and health over time. The topics covered include information on consumers with respect to the following: awareness of the relationship between salt/sodium intake and health; belief about the importance of the relationship to self and behavior intentions; accuracy of perceptions of sodium intake; use of nutrition label information; and use of table salt. Awareness of the Relationship Between Salt/Sodium Intake and Health An awareness of a diet/health relationship is generally considered a first step in motivating consumers to make dietary changes (Derby and Fein, 1995). As shown in Figure 2-1, a 1979 survey conducted by FDA showed that only 12 percent of Americans mentioned salt or sodium as a FIGURE 2-1 Consumer awareness of the relationship between salt/sodium intake and high blood pressure, 1979–2002. NOTES: Teisl et al. (1999) expressed results as the mean of reported responses among men and women. The response for the total population in 2002 was calculated by multiplying the percentage of respondents reporting they had heard of dietary factors being related to high blood pressure (75 percent) by 0.526, the proportion of those who had heard of dietary factors related to high blood pressure and who identified salt/salty foods/sodium as the dietary factor (FDA, 2007). SOURCES: 1979 and 1982: Heimbach, 1985; 1984–1994: Teisl et al., 1999; 2002: FDA, 2007.
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Strategies to Reduce Sodium Intake in the United States likely cause of high blood pressure (Heimbach, 1985). In a 1982 follow-up survey, this level rose to 34 percent (Heimbach, 1985). The levels vacillated between 43 and 48 percent between 1984 and 1994 (Teisl et al., 1999) and subsequently dropped to 39 percent in 2002 (FDA, 2007). Teisl et al. (1999) conceptualized the question of awareness as the relative position of a response in a hierarchy of responses, not a simple knowledge of a particular diet/health relationship (Teisl et al., 1999). The authors stated that declines in the awareness value “are evidence of competing messages, concerns about credibility, and/or habituation, not of decreased knowledge or understanding.” Overall, this suggests that consumer awareness of the relationship between sodium/salt intake and health increased as the large-scale educational programs from Table 2-1 were implemented, but creating awareness in the U.S. population to levels greater than 50 percent may be difficult to achieve. Additionally, the results suggest that it may be difficult to sustain a relatively high level of awareness for a topic such as sodium and high blood pressure over long periods of time. While almost half of U.S. consumers were aware of the link between salt/sodium intake and high blood pressure during the decade from 1984 to 1994, fewer made the link between salt/sodium intake and heart disease and heart attacks. In USDA’s 1989–1991 Diet and Health Knowledge Survey, 57 percent of meal planners and preparers recognized the risk for hypertension8 whereas only 26 percent recognized the risk for heart disease9 (Cypel et al., 1996). Comparable questions in the 1994–1996 survey found that the higher recognition of the salt/sodium relationship to blood pressure compared to heart disease persisted (51 percent for hypertension and 24 percent for heart disease) (Tippett and Cleveland, 2001). FDA’s 2002 Health and Diet Survey also reported a greater awareness of high blood pressure or hypertension than heart disease (39 percent for hypertension and 7 percent for heart disease or heart attack)10 (FDA, 2007). However, this more recent survey also suggested lower percentages of awareness of salt/sodium and disease relationships (i.e., 39 and 7 percent, respectively) than had been observed in the earlier surveys (i.e., 51 and 24 percent, 8 Fifty-seven percent is calculated by multiplying 86.8 (the percentage of persons who reported hearing of health problems being related to how much salt or sodium a person eats) by 0.653 (the proportion of the subgroup who identified hypertension as the health problem). 9 Twenty-six percent is calculated by multiplying 86.8 (the percentage of persons who reported hearing of health problems being related to how much salt or sodium a person eats) by 0.301 (the proportion of the subgroup who identified heart disease as the health problem). 10 Thirty-nine percent is calculated by multiplying 75 (the percentage of persons who reported hearing of high blood pressure being related to dietary intakes) by .526 (the proportion of the subgroup who identified salt, salty foods, or sodium). Seven is calculated by multiplying 83 (the percentage having heard of heart disease or heart attacks being related to dietary intakes) by 0.079 (the proportion who mentioned salt, salty foods, or sodium).
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Strategies to Reduce Sodium Intake in the United States of common methods of collecting data and accounting for use over time. The disadvantage of using disappearance data to estimate nutrient intake is that it overestimates intake because it fails to capture food losses and wastage after the nutrient enters the food system (e.g., cooking and processing losses). Salt disappearance data can be used to estimate time trend patterns in the availability of sodium for human consumption. The Salt Institute posts information on its website about food-grade salt sales in the United States.15 These data are most useful if the tonnage of salt is converted to milligrams of sodium. With changing population numbers over time, it is also useful to convert annual results to per capita values. The annual per capita sodium disappearance numbers from 1978 through 2008 derived from data on salt disappearance are illustrated in Figure 2-12. The salt disappearance data show a steady increase in per capita availability between 1983 and 1998. More recently, values appear to be leveling off or decreasing slightly. The peak levels in 1998 indicate that approximately 5,700 mg of sodium were available per person per day. The extent to which the disappearance values are an overestimation of actual intake is unknown but the fact that they are more than double the Dietary Guidelines for Americans level of < 2,300 mg/d sodium suggests that salt availability is in excess of public health goals for sodium. Moreover, given that the major advantage of disappearance data is the trend pattern that they reveal, the disappearance data in Figure 2-12 do not show a sustained reduction in response to the sodium-related public health initiatives identified in Tables 2-1 to 2-3. Although the pattern of use over time suggests that early educational and program initiatives carried out in the 1980s were associated with a reduction in salt use, subsequent programs—including the implementation in 1993 of mandatory declaration of sodium content on all food labels and multiple calls since 1969 for food processors to reduce the sodium content of foods—appear to have had little or no impact on salt availability for human use. Intake by Individuals Since 1971, NHANES has provided estimates of individuals’ nutrient intakes from a nationally representative sample of the U.S. population. These estimates are based on 24-hour recalls. As shown in Figure 2-13, the trends in sodium intake between the 1971–1974 and 2005–2006 surveys are shown for three life stage groups. Similar patterns were seen across other life stage groups (Briefel and Johnson, 2004; see Chapter 5). 15 Available online: http://www.saltinstitute.org/Production-industry/Facts-figures/U.S.-production-sales (accessed November 16, 2009).
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Strategies to Reduce Sodium Intake in the United States FIGURE 2-12 Annual per capita sodium disappearance based on salt disappearance, 1978–2008. NOTES: Sodium (milligrams) shown on y-axis was determined by the following calculation: Salt disappearance data (tons of food-grade salt per year) was converted to grams of salt per day. That number was then divided by census-based per capita population estimates used by USDA’s Economic Research Service in developing nutrient availability databases, 1978–2008, and grams of salt consumed per day was converted to milligrams sodium by multiplying by 39.3 percent. SOURCE: Based on Salt Institute salt disappearance data (tons of food-grade salt per year) and USDA census data. The results in Figure 2-13 suggest that intake increased between 1971–1974 and 1988–1994 and then plateaued between 1988–1994 and 2005–2006. Whether the early increases are real or due to methodological artifacts is uncertain. There were improvements in interview methodologies during that time that were associated with more complete reporting of intake (Loria et al., 2001). However, even with the caveat that intake by individuals tends to be underestimated and caution as to possible methodological sources of underestimation in the early surveys, the mean intakes, except for adult women in the first two survey periods, are all in excess of Dietary Guidelines for Americans recommendations. One way of crudely evaluating whether or not underreporting biases have influenced time trends in estimates of sodium intake is to evaluate whether the differences in sodium intake over time and among subgroups are negated or minimized when the results are expressed as sodium densities. Using the same database as in Figure 2-13, Figure 2-14 provides data on the sodium densities for the same surveys.
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Strategies to Reduce Sodium Intake in the United States FIGURE 2-13 Trends in mean sodium intake from food for three gender/age groups, 1971–1974 to 2003–2006. NOTES: Analyzed using 1-day mean intake data for NHANES 2003–2006 to be consistent with earlier analyses and age-adjusted to the 2000 Census; includes salt used in cooking and food preparation, but not salt added at the table. d = day; mg = milligram. SOURCES: Briefel and Johnson (2004) for 1971–2000 data; NHANES for 2003–2006 data (see Chapter 5). FIGURE 2-14 Trends in mean sodium intake densities from food for three gender/age groups, 1971–1974 to 2003–2006. NOTES: Analyzed using 1-day mean intake data for NHANES 2003–2006 to be consistent with earlier analyses and age-adjusted to the 2000 Census; includes salt used in cooking and food preparation, but not salt added at the table; 1-day mean intake calculated using the population proportion method. kcal = calorie; mg = milligram. SOURCES: Briefel and Johnson (2004), for 1971–2000 data; NHANES for 2003–2006 (see Chapter 5).
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Strategies to Reduce Sodium Intake in the United States As shown in Figure 2-14, the differences in sodium intake that were observed among children and adult men and women disappear to a large degree when the intakes are expressed as sodium densities. This suggests that the intake differences among life stage groups at any time were related primarily to differences in their energy intake rather than to differences in the sodium densities of the foods they consumed. The increasing sodium densities between the 1970s and late 1980s also show that foods as consumed contained higher amounts of sodium between those time periods. However, since the early 1990s sodium densities appear to be stable. Although data are not available to allow the separation of the relative contribution of increasing energy intake over time (or improved measures of energy intake over time) from the relative contribution of increasing amounts of sodium in foods over time, these data suggest that at least some of the increases in sodium intake over time may be due to increases in the amount of sodium in foods. Changes in intake over time must be cautiously interpreted because of limitations in these data, particularly older data based on different methodologies. However, compared to a sodium intake density of < 1,150 mg/1,000 calories per day to be consistent with a Dietary Guidelines for Americans daily intake of < 2,300 mg sodium and assuming a 2,000-calorie reference diet, most groups had intakes that exceeded guideline levels, even during the earlier periods when sodium densities appeared lower than in more recent years. Urinary Excretion of Sodium As described in Chapter 5, mean urinary sodium excretion collected over a 24-hour period is generally considered to be the gold standard for accurately estimating the sodium intake of individuals. However, in the absence of such data from nationally representative surveys in the United States, the best source of data on urinary sodium excretion of Americans is carefully designed and monitored research studies. Results for U.S. adults participating in two observational studies and four clinical trials between 1980 and the late 1990s indicate that the median urinary sodium excretion per 24 hours across all studies was approximately 3,700 mg/d for men and 3,000 mg/d for women (Loria et al., 2001). Based on the average sodium excretion across all studies, all but one group had sodium excretions of more than 2,300 mg. Eleven of 12 groups of men had average sodium excretion levels greater than 3,000 mg/d, with 4 of these groups having a mean excretion greater than 4,000 mg/d. For women, 6 of 12 groups had sodium excretions between 2,500 and 3,000 mg/d; 6 of the 12 groups had sodium excretions between 3,000 and 3,612 mg/d. Thus, the sodium excretion of U.S. adults participating in research studies showed that almost all of the groups had mean sodium excretion levels well in excess of the
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Strategies to Reduce Sodium Intake in the United States Dietary Guidelines for Americans recommendation of < 2,300 mg/d of sodium. Prevalence of Hypertension A solid body of diverse evidence has documented that, on average, as sodium intake rises, so does blood pressure. Furthermore, trials in children, non-hypertensive adults, and hypertensive adults have documented that sodium reduction lowers blood pressure. Although elevated blood pressure and hypertension are also related to other risk factors, reducing daily sodium intake is associated with significant reductions in population-based blood pressure values and prevalence of stroke mortality (DGAC, 2005). What have been the time trends in prevalence of hypertension among U.S. adults over the past several decades? National trends in the prevalence of hypertension of men and women 20 years of age and older from three different time periods are shown in Figure 2-15. Hypertension was defined as an elevated blood pressure (systolic pressure ≥ 140 mm Hg or diastolic pressure ≥ 90 mm Hg) and/or use of antihypertensive medications at the time of the individual’s examination in FIGURE 2-15 Trends in elevated blood pressure/hypertension from NHANES for persons ≥ 20 years of age. NOTES: Hypertension, as defined by the data source, is an elevated blood pressure (systolic pressure ≥ 140 mm Hg or diastolic pressure ≥ 90 mm Hg) and/or use of anti-hypertensive medications; data age-adjusted to 2000 population. SOURCE: NCHS, 2009.
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Strategies to Reduce Sodium Intake in the United States the NHANES Medical Examination Center (NCHS, 2009). Results were age-adjusted to the 2000 population. The results show an increase from 1988–1994 to 2003–2006 for both men and women (NCHS, 2009). Similar trends were seen across race/ethnicity groups and different income levels. Using age-standardized data from NHANES 1988–1994 and 1999–2004, Cutler et al. (2008) reported a relative increase of 18 percent in hypertension prevalence rates (from 24.4 to 28.9 percent). None of the age/gender or race/ethnicity groups in their analyses had declining prevalence rates. After adjusting for changes in body mass index (BMI) over the two surveys, there continued to be large relative increases in the prevalence of hypertension for women. These results indicate that some of the increases of hypertension in women were attributable to factors other than increases in BMI. These factors may have included increases in sodium intake, changes in alcohol and potassium intake, decreases in physical activity, suboptimal health literacy levels, and lack of access to health-care services. For men, increases in BMI accounted for most of the increased prevalence of hypertension between surveys. Thus, after controlling for BMI, prevalences of hypertension between 1988–1994 and 1999–2004 remained relatively stable for men and increased for women. In summary, the prevalence of hypertension in the U.S. population appears to be increasing. Controlling for the possible confounding effects of increasing body weight over the same time suggests that the prevalence is stable for men but increasing for women, even after controlling for obesity. However, neither the stable prevalence pattern seen for men nor the increasing pattern seen for women is consistent with a declining pattern of hypertension prevalence that would be expected to be associated with significant reductions in sodium intake on a population-wide basis. FINDINGS From the descriptions in this chapter, it is clear that a myriad of sodium reduction strategies, programs, and initiatives have been implemented by numerous government agencies, health professional organizations, and the food industry—starting in 1969 and continuing to the present. These programs had common themes and a consistent message on the relationship between sodium intake and hypertension, with special emphasis on consumer education, sodium labeling of food products at point of purchase, and encouragement of reformulation by food processors and more recently by restaurant/foodservice operators. Audiences for these programs and initiatives included consumers, health professionals, the media, and the food industry. To assess whether relevant population- and industry-based changes occurred during the 40 years since the first strategies, programs, and ini-
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Strategies to Reduce Sodium Intake in the United States tiatives were begun, trends have been evaluated in several relevant areas: consumer awareness, knowledge, and behavior; the food industry; sodium intake; and the prevalence of hypertension. To assess changes over time, available data from the National Nutrition Monitoring System and, in a few cases, the scientific or trade literature were used. Despite the fact that the publicly available data were somewhat spotty and incomplete in all of the areas examined, the totality of available evidence reveals a consistency of findings across those areas. From the available data, it is clear that past initiatives and recommendations have not been successful in achieving the ultimate goal of reducing sodium intake and sodium-related health concerns. Initially, consumer messages most strongly encouraged higher-risk groups (e.g., African Americans and older adults) to reduce sodium intake, and use of salt at the table and during cooking was emphasized. As evidence became stronger that sodium should be a concern throughout the lifespan and as new data emerged on major sources of intake, messages were adjusted to include the entire population, and to encourage consumers to consume processed and restaurant/foodservice foods that were lower in sodium. The results from the three different types of exposure estimates (salt disappearance, dietary recall, and urinary excretion) all consistently show that, despite the broad-based and long-term efforts, neither the salt disappearance nor the sodium intake data show a sustainable trend in declining sodium intake over the 40 years of carrying out the past and existing initiatives. Today, sodium intake by Americans is well in excess of the Dietary Guidelines for Americans recommendation of < 2,300 mg/d sodium. Similarly, significant declines in the prevalence of high blood pressure and stroke mortality have not been seen in the United States. While the ultimate goal of sodium reduction initiatives has not been met, intermediate goals have seen some success. Public education campaigns in the early 1980s created a dramatic rise (from 12 percent to 48 percent) in consumer awareness of the relationship between sodium and hypertension. Many consumers also believed that sodium reduction was an issue of personal importance, with 62 percent of main meal preparers saying they were personally concerned about sodium. Over a third of the population has been found to always or often use sodium information on the Nutrition Facts panel. Past initiatives also saw some success in motivating the food industry to reduce sodium in some of its products, and make sodium content claims to indicate lower sodium options to consumers. Given these changes, the question becomes, what has kept the population from achieving actual reductions in intake. As will be discussed elsewhere in this report, notably in Chapter 6, consumers live in a broad food environment in which social, organizational, and macro-level factors influence the types of foods consumed and, thus,
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Strategies to Reduce Sodium Intake in the United States sodium intake. The broad food environment can be linked to the reasons for the lack of effectiveness of 40 years of sodium reduction initiatives. The food supply itself is a key obstacle for consumers. The sodium densities of available foods—both in the marketplace and from restaurant/foodservice operations—make it difficult for consumers to meet dietary recommendations. Further, sustainability of consumer interest and concern is an obvious problem. This becomes intertwined with food producer interest in developing lower-sodium products and in using sodium-related claims and advertising. As a result of these developments, there is a manifest role for increased use of foods naturally low in sodium (e.g., fruits, vegetables) as well as linkages to other public health initiatives because of increasing portion size. Importantly, the number of food channels outside the home and the pervasiveness of salt use throughout the food supply—with average sodium intake density well in excess of that recommended by the Dietary Guidelines for Americans—make it very difficult for consumers and meal planners to achieve recommended sodium intake. Overall, the outreach and educational efforts to date have failed to reduce the sodium intake of the American public; unfortunately, a lack of available data regarding the implementation and evaluation of these efforts prevents the drawing of firm conclusions about why they did not succeed. Currently, sodium intake remains well in excess of the goals in the Dietary Guidelines for Americans. It is now apparent that outreach and educational programs to consumers and food producers, although a necessary component of any strategy, are insufficient by themselves to achieve the public health goal of reducing sodium intake by Americans to < 2,300 mg/d. A new focus on changing the food supply to better enable consumers to reduce sodium intake may result in better outcomes in the future. While not completely analogous to sodium reduction, experiences with folic acid suggest a role for food supply changes in achieving public health goals. Years of educational efforts failed to make a significant impact on the intake of folic acid by the at-risk population (women of childbearing age). However, once folic acid fortification was instituted, folic acid intake increased without behavior changes (Johnston and Staples, 1995; Pfeiffer et al., 2007). At the same time, consumers have a role to play: the impact of any food supply approach can be enhanced by informed consumer choices. Therefore, efforts to ensure this role is supported may benefit from activities that are now more fully researched, better designed, and effectively implemented than past efforts. REFERENCES Alderman, M. H. 2010. Reducing dietary sodium: The case for caution. Journal of the American Medical Association 303(5):448-449.
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