Guiding Principles for Developing Dietary Reference Intakes Based on Chronic Disease (2017) / Chapter Skim
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Appendix B: Options Report
Appendix B: Options Report
Pages 257-294
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Appendix B Options Report 257
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How- stances as well as relevant chronic disease outcomes. The increasing ever, it has proved to be more challenging to base DRI values on chronic disease endpoints; deviations from the traditional framework were often 1 This is a report based on working group meetings held between Novemrequired, and in some cases, DRI values were not established for intakes ber 2014 and April 2016 and a public workshop titled "Options for Considthat affected chronic disease outcomes despite evidence that supported eration of Chronic Disease Endpoints for Dietary Reference Intakes (DRIs)
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What are the important evidentiary challenges for select- between food substances and chronic diseases in observational ing and using chronic disease endpoints in future DRI re- studies is particularly challenging because the assessment views? of intake is most often based on self-reported dietary intakes, which are subject to systematic bias, particularly intakes of 2)
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This would intake value for the chronic disease risk, if the confidence in the increase the number of relations between food substances and data is at an acceptable level. chronic disease outcomes for which committees could establish DRIs but is associated with considerable uncertainty as to Options for types of reference values whether the relation of the food substance and the chronic disease is causal.
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Several descriptive options are proposed for dealing with Arguments for or against including chronic disease endpoints this issue. One option is to ensure that no point estimate or range in future DRIs of beneficial intakes for chronic disease risk reduction extends beyond the intake at which the risk of adverse events, including Evidence-based reference intake values and/or recommendachronic diseases, increases.
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DRIs are available for 22 groups based on Options for starting point age, sex, pregnancy, and lactation in apparently healthy pop The starting point of current DRI processes is individual food ulations. Future DRI committees might need to review whether substances, and all pertinent outcomes related to varying intakes the population coverage should be expanded to include morof given food substances are considered.
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DRI reports focus on the scientific and public health produced these reports recognized that the EAR and RDA aspects of the intakes of nutrients and food substances, but they model and the UL model were inappropriate for some outcomes do not make policy recommendations, with one notable excepof interest. Therefore, DRI committees added new reference tion.
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Options for establishing intake-response apparently healthy population. relations between food substances and chronic disease endpoints are the focus of section VI.
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lenge is the limited availability of RCTs that are designed to establish that a food substance of interest is causally related to a given chronic disease outcome. A much larger body of evidence Key question 3: What are the arguments for and against based on prospective cohort and other observational studies is continuing to include chronic disease endpoints in future DRI available that shows associations between food substances and reviews?
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. TABLE 4 Traditional and chronic disease endpoints for DRIs1 Eligibility for Issue consideration Focus Characteristics Expression of risk Traditional endpoints Food substances that Nutrient Adequate intakes are essential Average inflection point between are essential or requirements for preventing and treating adequate and inadequate intakes (EAR)
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and the quantity of This section and the next 2 sections discuss ways to assess the available studies usually declines. Within each level, however, strength of the evidence on causal relations between food substances quality varies by study design and implementation, which can of interest and targeted chronic diseases.
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substance on the chronic disease. DRI committees have used LDL-cholesterol concentrations as a surrogate disease marker for coronary heart disease and blood pressure as a surrogate Study designs marker for CVD (15, 23, 24)
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Below, we integrate the perspectives of past evolving science provided new insights into how study designs DRI committees and newer science as to the potential usefulness can affect evaluations of relations between food substances and of types of study designs for DRI contexts.
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RCTs intakes to determine exposures in observational studies. Dietary RCTs with a chronic disease event or qualified surrogate disease assessments need only provide assurance that a trial has adequate marker as the primary outcome.
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lations between food substances and chronic diseases is relatively The study follow-up period is typically short relative to the common, and many more studies use such outcomes than RCTs period of food-substance exposure preceding the initiation of with a clinical event or a qualified surrogate disease marker as the study. the primary outcome.
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marker is qualified for its intended purposes. for the confounding effects of these temporal changes when evaluating relations between food substances and chronic chronic diseases.
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calculate the amounts of food substances that participants con- The inclusion of all relevant research and the use of a priori sume from self-reports of food and supplement intakes. In- criteria for judging study quality minimize study-related teractions between food substances make it difficult to determine biases and enhance transparency.
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Effects on responsiveness to dietary intervention and effect sizes It is then possible to evaluate the strengths and weaknesses of each study type for a given relation between food substances and Various inherited and acquired subject characteristics and chronic diseases. contextual factors may influence responsiveness to exposures of interest.
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For tensive experience with its use. Disadvantages are that it is not example, they can highlight biologically important interactions outcome specific, not sufficiently inclusive of study characterthat DRI committees need to take into account when setting istics that are relevant to food substance and dietary studies, and reference values.
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Cross-sectional study SIGN 50 cohort or case-control (http:// ROBINS for cross-sectional studies is in development www.sign.ac.uk/methodology/ checklists.html) 1 AMSTAR, A Measurement Tool to Assess Systematic Reviews; RCT, randomized controlled trial; ROBINS, Risk of Bias in Nonrandomized Studies; ROBIS, Risk of Bias in Systematic Reviews; SIGN 50, Scottish Intercollegiate Guidelines 50.
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As with any synthesis of information on a population health risk issue, there is a need to carefully evaluate Food-substance applications the available information and weigh the available evidence for The AHRQ uses the AHRQ Methods Guide to grade the causality in reaching conclusions about the association between strength of the evidence for each outcome in a systematic review food substances and chronic disease endpoints.
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. However, few RCTs However, DRI committees have rarely chosen these types of outdesigned to evaluate the relation of food substances to chronic comes to establish a DRI value on the basis of a chronic disease diseases have used a chronic disease event as the outcome measure.
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those between food substances and chronic disease endpoints (Table 4)
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Past DRI committees used data from observational whereas the relation between a food substance and a chronic studies, which contain the biases described earlier in this report, disease indicator can be more diverse (e.g., linear, monoprimarily to calculate the relations between food substances tonic, or nonmonotonic)
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The background risk of a given chronic approach typically requires usable intake-response data from disease is not zero. "Substances" could be individual food substances or RCTs, which is probably impractical because most RCTs have groups of interacting substances.
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. Adaptation 3 is for food substances that have causal relations As DRI committees consider possible approaches to establish at different intake levels to multiple chronic diseases.
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reason why basing ULs on chronic disease endpoints is so An advantage of this option is that DRI committees could challenging is that the traditional UL definition is based on an establish CD point estimates for specified risk reductions for $1 intake level associated with no increase in absolute risk, whereas chronic disease, which would provide flexibility to both com- most data related to chronic disease risk are expressed as relative mittees and users. This adaptation may make it easier than the risk.
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A strength of this adaptation is that it the minimum level of severity and prevalence of targeted chronic acknowledges that the relation between food substances and diseases and the degree of risk reduction associated with specified chronic diseases might be continuous and not have a threshold. intakes.
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The advantage of this approach is that it allows multiple, food substances and chronic diseases. Such a framework takes and possibly different, intake-response relations between the into account the role of biological mechanisms in establishing intake of a food substance and a chronic disease endpoint to be quantitative reference intakes.
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Therefore, the extrapolation of DRI values based on this complexity, some food substances (e.g., short-chain fatty chronic disease endpoints might be more challenging than of acids, vitamin D, vitamin K, and folate) have nondietary sources, those based on deficiency disease criteria.
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. DRI committees must often express present framework to chronic disease endpoints and the reference values for chronic diseases as reductions in specific expanding understanding of the pathophysiology of diseases of relative risks that vary by intake.
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The FNB or a government agency could appoint a new diseases. committee to establish reference values on the basis of chronic disease endpoints, or an existing group that is independent of the Option 2: Establish DRIs for multiple food substances on the National Academies of Sciences, Engineering, and Medicine basis of a chronic disease endpoint (e.g., expert panels from chronic disease societies or standing This approach requires a different paradigm than the one that government advisory committees)
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, and this curve provides ample, in stored biospecimens -- to analyze prospective cohort a possible benchmark for establishing dietary reference intake data in a case-control mode. values for food substances with U-shaped intake-response re lations.
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Comprehensive DRIs are based on reduction in chronic disease risk may be system frameworks would be necessary that link dietary patterns needed. and intakes of specific food substances to food-substance ab- The report also highlights several research opportunities that sorption, metabolism, bioactivity, excretion, tissue uptake, and are key to the derivation of future DRIs based on chronic disease function along with a variety of metabolic and functional health endpoints (Table 10)
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Taylor CL. Framework for DRI development components "known" ation of chronic disease endpoints for Dietary Reference Intakes and components "to be explored" background paper.
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Consideration of Chronic Disease Endpoints for Dietary Reference 56. Clarke R, Halsey J, Bennett D, Lewington S
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2015 [cited Reference Intakes. 1997 [cited 2016 May 3]
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Modeling U-shaped water to measurement of human energy expenditure. J Nutr 1999;129: exposure-response relationships for agents that demonstrate toxicity 1765–8.
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