- Email: [email protected]
Is the science behind the 2010 Dietary Guidelines for Americans “unquestioned?”
Nutrition 27 (2011) 385–386
Contents lists available at ScienceDirect
Nutrition journal homepage: www.nutritionjrnl.com
Editorial
Is the science behind the 2010 Dietary Guidelines for Americans “unquestioned?”
The 2010 Dietary Guidelines for Americans were released on January 31, 2011 with a great deal of anticipation. Although these guidelines have been commended by organizations such as the American Dietetic Association, others remain critical. In the October 2010 issue of Nutrition, a critique was published of the report of the Dietary Guidelines Advisory Committee, which assembles the evidence on which the final recommendations are based. This critique closely examined the process used to develop the guidelines, finding many flaws that would limit their effectiveness in addressing our nation’s current health crisis [1]. This process included the use of a newly created US Department of Agriculture (USDA) Nutrition Evidence Library, with the laudable intent to base the new guidelines on the full body of evidence. Despite this, neither the Dietary Guidelines Advisory Committee report nor the final guidelines met the evidence-based standards suggested in the statement that the “the science behind the guidelines is unquestioned” [2]. Regardless of their stance on the nutritional recommendations contained in the guidelines, experts on both sides of the issue agree that the process for creating our dietary guidelines is as much political as it is scientific [3,4], indicating that is unlikely that that the science the recommendations represent is no longer a matter of debate. The first dietary guidelines were based on the 1977 Dietary Goals for Americans. Although this document, the first of its kind in our nation’s history, acknowledged that the changes in the American diet that the Dietary Goals proposed were radical, it also asserted that they presented no risk to the health of the American people: “What are the risks associated with eating less meat, less fat, less saturated fat, less cholesterol, less sugar, less salt, and more fruits, vegetables, unsaturated fats and cereal productsdespecially whole grain cereals? There are none that can be identified and important benefits can be expected” [5]. Yet even at the time, the American Medical Association expressed concern that, “The evidence for assuming that benefits to be derived from the adoption of such universal dietary goals as set forth in the Report is not conclusive and there is potential for harmful effects from a radical long-term dietary change as would occur through adoption of the proposed national goals” [6]. The underlying concern with the 2010 Dietary Guidelines is that the evidence for concluding that this dietary pattern will produce health benefits continues to be absent, a fact recognized in the guidelines themselves: “The USDA Food Patterns identify daily amounts of foods, in nutrient-dense forms, to eat from five major food groups and their subgroups. . Though they have not been specifically tested for health benefits, they are similar to the DASH research diet and consistent with most of the 0899-9007/$ - see front matter Ó 2011 Elsevier Inc. All rights reserved. doi:10.1016/j.nut.2011.02.005
measures of adherence to Mediterranean-type eating patterns” (emphasis added) [7]. Within the USDA, which assumes the lead in nutritional policy in most matters, there is no system for evaluating the health outcomes of its own recommendations. The USDA does, however, monitor the dietary intakes of Americans. In the 30 y since the original guidelines were published, the eating patterns of Americans have changed in the recommended directions: carbohydrate consumption has increased; overall fat, saturated fat, and cholesterol consumption have decreased to near or below targeted levels; caloric intake remains within recommended levels; and leisure time physical activity has increased slightly [8]. At the same time, “overweight and obesity in the US has increased dramatically in the past thirty years, while the number of Americans diagnosed with type 2 diabetes has tripled” [9]. The Dietary Guidelines cannot and should not be blamed for creating the obesity crisis. The low-fat recommendations that the guidelines have been promoting for the past 30 y were originally based on a “best guess” and were issued with genuine concern for the health and welfare of the people of America. The issuing agencies could not have anticipated the changes in the food supply, the effect on the eating habits of Americans, and the advances in science that would occur after the initial guidelines were released. However, at this point, we must view the effects of the Dietary Guidelines through the lens of an “intention-to-treat” analysis. This sort of analysis answers “the public health question of what happens when a recommendation is made to the general public and the public decides how to implement it. The results of an intention-to-treat analysis can be quite different from the treatment effect observed when adherence is perfect” [10]. Intention-to-treat analysis disregards the question of whether or not the diet is effective if adhered to, which may or may not be the case, but simply addresses the question of what happens when people are given this advice. In evaluating the effect of the implementation of the Dietary Guidelines for Americans in this manner, we must acknowledge that it has not had the desired effect on decreasing chronic disease and, in fact, we must consider that the “potential for harmful effects” has in fact been realized. That the guidelines have not had their intended effect, taken in conjunction with the evidence that the current Dietary Guidelines appear to have been created without an objective review of all available science, leaves unanswered the question as to why the USDA would insist on maintaining the status quo recommendations that have been in place since the history of dietary guidelines began. An explanation may lie in the
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A. H. Hite / Nutrition 27 (2011) 385–386
possibility that acknowledging current science and revising its long-established pattern of recommendations in light of our country’s current health outcomes would run counter to the USDA’s primary mandate to promote the use of US agricultural products. The USDA should not be assigned the task of promoting US agricultural products and protecting the health of the American people. This potentially places the USDA in a conflict of interest that hampers its ability to accomplish either mandate effectively. Until and unless the actual health outcomes of the Dietary Guidelines are fully evaluated and the guidelines are developed from an objective review of all available science, America will be best served by moving the process of creating the guidelines to an independent agency. References [1] Hite AH, Feinman RD, Guzman GE, Morton M, Schoenfeld PA, Wood RJ. In the face of contradictory evidence: report of the Dietary Guidelines for Americans Committee. Nutrition 2010;26:915–24. [2] United Sates Department of Agriculture. USDA and HHS announce new dietary guidelines to help Americans make healthier food choices and confront obesity epidemic. Press conference video transcript. Available at: http://ocbmtcreal.usda.gov/player/player.html?base¼http://ocbmtcreal.us da.gov/&uri¼/USDA/secy&stream¼secy013111a. Accessed January 31, 2011. [3] Marantz PR, Bird ED, Alderman MH. A call for higher standards of evidence for dietary guidelines. Am J Prev Med 2008;34:234–40.
[4] Woolf SH, Nestle M. Do dietary guidelines explain the obesity epidemic? Am J Prev Med 2008;34:263–6. [5] Select Committee on Nutrition and Human Needs of the United States Senate. Dietary goals for the United States. 2nd ed. Washington, DC: US Government Printing Office; 1977. [6] American Medical Association. Dietary goals for the United States: statement of the American Medical Association to the Select Committee on Nutrition and Human Needs, United States Senate. R I Med J 1977;60: 576–81. [7] US Department of Agriculture and US Department of Health and Human Services. Dietary guidelines for Americans; 2010. Available at: http:// www.cnpp.usda.gov/DGAs2010-PolicyDocument.htm. Accessed January 31, 2010. [8] United States Department of Agriculture. Report of the Dietary Guidelines Advisory Committee on the Dietary Guidelines for Americans; 2010. Available at: http://www.cnpp.usda.gov/DGAs2010-DGACReport.htm. Accessed July 2010. [9] Centers for Disease Control and Prevention (CDC). National Center for Health Statistics, Division of Health Interview Statistics, data from the National Health Interview Survey. Available at: http://www.cdc.gov/ diabetes/statistics/prev/national/figpersons.htm. Accessed 15 August 2010. [10] Dallal GE. “Intention-to-treat analysis”. The little handbook of statistical practice. Available at: http://www.jerrydallal.com/LHSP/itt.htm. Accessed February 2, 2011.
Adele H. Hite, M.A.T. University of North Carolina at Chapel Hill Chapel Hill, NC, USA E-mail address: [email protected]
Contents lists available at ScienceDirect
Nutrition journal homepage: www.nutritionjrnl.com
Editorial
Is the science behind the 2010 Dietary Guidelines for Americans “unquestioned?”
The 2010 Dietary Guidelines for Americans were released on January 31, 2011 with a great deal of anticipation. Although these guidelines have been commended by organizations such as the American Dietetic Association, others remain critical. In the October 2010 issue of Nutrition, a critique was published of the report of the Dietary Guidelines Advisory Committee, which assembles the evidence on which the final recommendations are based. This critique closely examined the process used to develop the guidelines, finding many flaws that would limit their effectiveness in addressing our nation’s current health crisis [1]. This process included the use of a newly created US Department of Agriculture (USDA) Nutrition Evidence Library, with the laudable intent to base the new guidelines on the full body of evidence. Despite this, neither the Dietary Guidelines Advisory Committee report nor the final guidelines met the evidence-based standards suggested in the statement that the “the science behind the guidelines is unquestioned” [2]. Regardless of their stance on the nutritional recommendations contained in the guidelines, experts on both sides of the issue agree that the process for creating our dietary guidelines is as much political as it is scientific [3,4], indicating that is unlikely that that the science the recommendations represent is no longer a matter of debate. The first dietary guidelines were based on the 1977 Dietary Goals for Americans. Although this document, the first of its kind in our nation’s history, acknowledged that the changes in the American diet that the Dietary Goals proposed were radical, it also asserted that they presented no risk to the health of the American people: “What are the risks associated with eating less meat, less fat, less saturated fat, less cholesterol, less sugar, less salt, and more fruits, vegetables, unsaturated fats and cereal productsdespecially whole grain cereals? There are none that can be identified and important benefits can be expected” [5]. Yet even at the time, the American Medical Association expressed concern that, “The evidence for assuming that benefits to be derived from the adoption of such universal dietary goals as set forth in the Report is not conclusive and there is potential for harmful effects from a radical long-term dietary change as would occur through adoption of the proposed national goals” [6]. The underlying concern with the 2010 Dietary Guidelines is that the evidence for concluding that this dietary pattern will produce health benefits continues to be absent, a fact recognized in the guidelines themselves: “The USDA Food Patterns identify daily amounts of foods, in nutrient-dense forms, to eat from five major food groups and their subgroups. . Though they have not been specifically tested for health benefits, they are similar to the DASH research diet and consistent with most of the 0899-9007/$ - see front matter Ó 2011 Elsevier Inc. All rights reserved. doi:10.1016/j.nut.2011.02.005
measures of adherence to Mediterranean-type eating patterns” (emphasis added) [7]. Within the USDA, which assumes the lead in nutritional policy in most matters, there is no system for evaluating the health outcomes of its own recommendations. The USDA does, however, monitor the dietary intakes of Americans. In the 30 y since the original guidelines were published, the eating patterns of Americans have changed in the recommended directions: carbohydrate consumption has increased; overall fat, saturated fat, and cholesterol consumption have decreased to near or below targeted levels; caloric intake remains within recommended levels; and leisure time physical activity has increased slightly [8]. At the same time, “overweight and obesity in the US has increased dramatically in the past thirty years, while the number of Americans diagnosed with type 2 diabetes has tripled” [9]. The Dietary Guidelines cannot and should not be blamed for creating the obesity crisis. The low-fat recommendations that the guidelines have been promoting for the past 30 y were originally based on a “best guess” and were issued with genuine concern for the health and welfare of the people of America. The issuing agencies could not have anticipated the changes in the food supply, the effect on the eating habits of Americans, and the advances in science that would occur after the initial guidelines were released. However, at this point, we must view the effects of the Dietary Guidelines through the lens of an “intention-to-treat” analysis. This sort of analysis answers “the public health question of what happens when a recommendation is made to the general public and the public decides how to implement it. The results of an intention-to-treat analysis can be quite different from the treatment effect observed when adherence is perfect” [10]. Intention-to-treat analysis disregards the question of whether or not the diet is effective if adhered to, which may or may not be the case, but simply addresses the question of what happens when people are given this advice. In evaluating the effect of the implementation of the Dietary Guidelines for Americans in this manner, we must acknowledge that it has not had the desired effect on decreasing chronic disease and, in fact, we must consider that the “potential for harmful effects” has in fact been realized. That the guidelines have not had their intended effect, taken in conjunction with the evidence that the current Dietary Guidelines appear to have been created without an objective review of all available science, leaves unanswered the question as to why the USDA would insist on maintaining the status quo recommendations that have been in place since the history of dietary guidelines began. An explanation may lie in the
386
A. H. Hite / Nutrition 27 (2011) 385–386
possibility that acknowledging current science and revising its long-established pattern of recommendations in light of our country’s current health outcomes would run counter to the USDA’s primary mandate to promote the use of US agricultural products. The USDA should not be assigned the task of promoting US agricultural products and protecting the health of the American people. This potentially places the USDA in a conflict of interest that hampers its ability to accomplish either mandate effectively. Until and unless the actual health outcomes of the Dietary Guidelines are fully evaluated and the guidelines are developed from an objective review of all available science, America will be best served by moving the process of creating the guidelines to an independent agency. References [1] Hite AH, Feinman RD, Guzman GE, Morton M, Schoenfeld PA, Wood RJ. In the face of contradictory evidence: report of the Dietary Guidelines for Americans Committee. Nutrition 2010;26:915–24. [2] United Sates Department of Agriculture. USDA and HHS announce new dietary guidelines to help Americans make healthier food choices and confront obesity epidemic. Press conference video transcript. Available at: http://ocbmtcreal.usda.gov/player/player.html?base¼http://ocbmtcreal.us da.gov/&uri¼/USDA/secy&stream¼secy013111a. Accessed January 31, 2011. [3] Marantz PR, Bird ED, Alderman MH. A call for higher standards of evidence for dietary guidelines. Am J Prev Med 2008;34:234–40.
[4] Woolf SH, Nestle M. Do dietary guidelines explain the obesity epidemic? Am J Prev Med 2008;34:263–6. [5] Select Committee on Nutrition and Human Needs of the United States Senate. Dietary goals for the United States. 2nd ed. Washington, DC: US Government Printing Office; 1977. [6] American Medical Association. Dietary goals for the United States: statement of the American Medical Association to the Select Committee on Nutrition and Human Needs, United States Senate. R I Med J 1977;60: 576–81. [7] US Department of Agriculture and US Department of Health and Human Services. Dietary guidelines for Americans; 2010. Available at: http:// www.cnpp.usda.gov/DGAs2010-PolicyDocument.htm. Accessed January 31, 2010. [8] United States Department of Agriculture. Report of the Dietary Guidelines Advisory Committee on the Dietary Guidelines for Americans; 2010. Available at: http://www.cnpp.usda.gov/DGAs2010-DGACReport.htm. Accessed July 2010. [9] Centers for Disease Control and Prevention (CDC). National Center for Health Statistics, Division of Health Interview Statistics, data from the National Health Interview Survey. Available at: http://www.cdc.gov/ diabetes/statistics/prev/national/figpersons.htm. Accessed 15 August 2010. [10] Dallal GE. “Intention-to-treat analysis”. The little handbook of statistical practice. Available at: http://www.jerrydallal.com/LHSP/itt.htm. Accessed February 2, 2011.
Adele H. Hite, M.A.T. University of North Carolina at Chapel Hill Chapel Hill, NC, USA E-mail address: [email protected]