Global Harmonization of Methodological Approaches to Nutrient Intake Recommendations Proceedings of a Workshop (2018) / Chapter Skim
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3 Harmonization Frameworks
3 Harmonization Frameworks
Pages 21-42
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From page 21... ...
, she said, yet most data comparing nutrient intake and chronic disease endpoints come from observational studies. This difference 21
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. in the nature of the evidence that is available in the scientific literature is "not good or bad," MacFarlane said, "it just is what it is." Continuing the focus on chronic disease endpoints, King highlighted major findings from a recently published National Academies of Sciences, Engineering, and Medicine report, Guiding Principles for Developing ietary Reference Intakes Based on Chronic Disease (NASEM, 2017a)
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From page 23... ...
1 This section summarizes information presented by Peter Clifton, Ph.D., professor of nutri tion, University of South Australia, Adelaide, Australia. 2 The 2005–2006 NRV review process led to publication of Nutrient Reference Values for Australia and New Zealand in 2006.
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From page 24... ...
. As Clifton had previously alluded, stakeholders also reported that the ULs caused problems with Food Standards Australia New Zealand, A ustralia's food regulatory agency, and that the ULs needed to be justified, not just borrowed from the IOM recommendations.
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Regarding the latter, Clifton remarked that the people consulted certainly wanted a chronic disease prevention component included in the NRV process, but separate from nutrition deficiency diseases. Additionally, the framework committee recommended the following: • Clearly define and justify endpoints relevant for the assessment of nutrient deficiency and chronic disease prevention in advance of gathering the evidence.
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reference nutrient intake, however, has been set at 200 µg and the European Food Safety Authority population reference intake for folate at 330 µg. Clifton reiterated that all of these values rely on the same biochemical indicator.
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Clifton concluded, "So it would appear that whatever the population are eating now is certainly adequate." However, he continued, there is a bit of a mismatch between measured indicators of folate status versus intake indicators. Even with this virtually complete folate replete population, an estimated 10 percent of estimated intakes are below the EAR.
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endpoint, probably in the absence of any evidence or in the presence of only a small amount of evidence, or persuading the National Academies to lower its intake recommendations. ENDPOINTS: DIFFERENCES WHEN CONSIDERING DEFICIENCY VERSUS CHRONIC DISEASE5 In the 1990s, it was decided that Canada and the United States would move forward with a harmonized approach for setting nutrient reference values.
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Once the causal relationship is determined, the next step is to establish the intake–response relationship, that is, find data showing that there are changes in the endpoint of interest as nutrient intakes increase. Once an intake–response model is established, then the DRI can be set.
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Evidence of Causality: Deficiency Versus Chronic Disease Endpoints Again, MacFarlane continued, one of the assumptions of the DRI approach is that there is a causal relationship between nutrient intake and an endpoint. When establishing causality or an intake–response relationship, normally the gold standard evidence is from an RCT and, ideally, from systematic reviews and meta-analyses of many RCTs (see Figure 3-1)
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Biomarkers on the Causal Pathway: Deficiency Versus Chronic Disease Endpoints MacFarlane described that another assumption of the DRI framework is that there are biomarkers that are clearly on the causal pathway and that directly relate the intake status of a particular nutrient to the endpoint or disease of interest. She explained that examples of biomarkers on the clinical pathway include serum folate, serum 25(OH)
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So, again, an assumption of the DRI framework, in this case that every person of every life stage is affected by the same risk, does not apply when considering chronic disease. Another difference with chronic disease risk, she added, is that it is often defined as relative risk, rather than absolute risk.
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From page 33... ...
Thresholds for Adequacy and Upper Intake: Deficiency Versus Chronic Disease Endpoints Yet another assumption that applies to deficiency endpoints is that there is an inflection point between inadequate and adequate intake levels. Yet, nutrient–chronic disease relationships often do not have inflection points.
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"Where would you set a DRI value for this kind of nutrient? " Synopsis of the DRI Framework Approach The DRI approach works well for estimating adequate intakes and adverse effects for essential nutrients, but it has been more challenging when using chronic disease endpoints, MacFarlane recapped.
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The "Options Report": Differences Between Traditional DRIs and DRIs for Chronic Disease The charge of the Options Report committee was to address options for dealing with the challenges encountered when establishing DRIs for chronic disease endpoints and to provide future guidance to DRI committees for judging nutrients and other food substances and chronic disease risk. The first thing the committee had to do, King recalled, was think about how DRIs for the traditional nutrient recommendations differ from DRIs for chronic disease.
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Selecting and Judging the Chronic Disease Evidence The National Academies consensus committee made two sets of primary recommendations: (1) how to determine whether specific levels of nutrients and other food substances can ameliorate chronic disease risk; and (2)
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Structuring Chronic Disease DRIs According to King, in its 2017 report the consensus committee decided that a DRI for chronic disease risk should be a range, rather than a single number, because the risk for a chronic disease can be spread over a range of intakes. Additionally, the committee decided that if an increased chronic disease risk occurs only above the traditional UL, then there is no need to develop a DRI for chronic disease, because avoiding intakes above the UL will avoid that risk for chronic disease.
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Then, after the systematic review has been completed, a DRI committee will be appointed, possibly with the assistance of a subcommittee, to judge the evidence using the GRADE system and to determine if the relationship between sodium and a single chronic disease outcome is causal in populations similar to those described in the evidence review. The recommendation for chronic disease endpoints was that a DRI committee would establish an intake range, not a single number, where the sodium-related chronic disease risk is minimal.
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The committee decided that using those clinical endpoints is not going to be very helpful in terms of setting up a relationship with nutrient intakes, so they recommended looking for a surrogate marker instead. Clifton pressed his point further: Surrogate markers
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MacFarlane reiterated her expectation that more evidence will be coming from observational studies than from RCTs, given how few nutrition RCTs relate to particular nutrients and chronic disease endpoints. The challenge comes from the complexity of the development of chronic diseases over not just years, but decades, and the difficulty in estabishing an exposure relationship with those diseases.
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only 3 percent were folate deficient. She wondered if there were also any data showing what these same indi iduals' v folate intakes were prior to hospitalization so their RBC folate levels measured at the hospital could be correlated with folate intake estimates.
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From page 42... ...
Charrondiere also asked if there would be what she referred to as a "reality check" when chronic disease DRIs are set. That is, will there be an additional step to check to see that the DRIs are achievable with a healthy food intake?
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