Global Harmonization of Methodological Approaches to Nutrient Intake Recommendations Proceedings of a Workshop (2018) / Chapter Skim
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5 Exploring Approaches to Evaluating the Evidence
5 Exploring Approaches to Evaluating the Evidence
Pages 57-82
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From page 57... ...
He noted that an updated AMSTAR2 for use with nonrandomized studies in addition to RCTs, and thus of relevance to the types of reviews being discussed at this workshop, will be the latest QAI tool to the marketplace. "We have arrived at a stage in which the use and usefulness of systematic reviews to inform nutrition decisions are no longer debated," Joseph Lau claimed.
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From page 58... ...
. In closing, Lau emphasized the likelihood that different countries may need to convene their own expert panels to develop nutrient intake recommendations but with the different panels using the same systematic reviews.
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From page 59... ...
Verhagen emphasized, however, that the work of scientists is to describe risk–benefit relationships, in contrast to the work of policy makers which is to do something with that information. In fact, he noted, the government decided not to fortify with folic acid, but to supplement instead.
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From page 60... ...
Each of these buckets contains a number of different biases, he clarified. The selection bias bucket, for example, is not just selection bias, but also includes allocation bias, case mix bias, channeling bias, and so forth.
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From page 61... ...
. It became quite apparent during that process, Wells recalled, that the existing QAIs were not sensitive enough to evaluate nutrition evidence relating to chronic disease endpoints for Dietary Reference Intakes (DRIs)
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From page 62... ...
There was then some discussion about the items in Washington, DC, and then a panel was convened to refine the list of proposed items. Fourth, they decided on five nutrition-specific items for RCTs, five for cohort studies, and two for case-control studies.
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From page 63... ...
developed by Wells and colleagues for Health Canada with the same internal validity checklist as in the original SIGN 50 QAI, plus the newly developed nutrition-specific section and a revised overall assess ment section. SOURCES: Presented by George Wells, HMD Workshop, Rome, Italy, September 21, 2017 (adapted from SIGN, 2015)
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From page 64... ...
As an example of a risk-of-bias tool being used to evaluate RCTs, Wells mentioned the Cochrane Risk of Bias Tool, included in the Cochrane Handbook for Systematic Reviews of Interventions ("the Cochrane handbook") (Higgins and Green, 2011)
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From page 65... ...
nutrition-specific QAIs for RCTs, cohort studies, case-control studies, and cross-sectional studies; a nutrition-specific risk-of-bias tool (i.e., a bolt-on tool) ; and a nutrition-specific tool for evaluating systematic reviews (i.e., an AMSTAR2 bolt-on)
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From page 66... ...
"Because we are all human," he explained, the same evidence can be used to inform nutrient intake recommendations. Finally, conducting a systematic review is laborious and requires a significant amount of resources, including expertise, time, and money; thus, it is desirable to minimize replication of effort and to collaborate and share resources.
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From page 67... ...
Prepare the topic -- refine questions and develop an analytic framework 2. Search for and select studies -- identify eligibility criteria, search for relevant studies, and select evidence for inclusion 3.
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From page 68... ...
It is valuable in other ways as well, Lau continued: It uses experts efficiently; the framework and process can be open to public review, thereby providing transparency and minimizing biases; it can help to highlight what aspects are known and unknown; it can clarify which study designs (e.g., experimental or observational) may be best to address specific questions; and it can be used to facilitate future updates of systematic reviews as new evidence emerges.
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From page 69... ...
NOTE: BMC = bone mineral content; BMD = bone mineral density; BMI = body mass index; CVD = cardiovascular disease; UV = ultraviolet radiation. SOURCES: Presented by Joseph Lau, HMD Workshop, Rome, Italy, September 21, 2017 (reprinted with permission, Chung et al., 2009b)
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From page 70... ...
With this information, the systematic review team was then able to conduct its literature search. They reviewed more than 16,000 primary study citations and ended up selecting 165 of these, plus some additional systematic reviews.
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From page 71... ...
Of these, they reviewed 165 primary study articles (60 RCTs, 3 nonrandomized controlled trials, and 102 cohort or case-control studies) and 11 systematic reviews.
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From page 72... ...
Thus, there is a need to monitor new evidence and to have a process for updating systematic reviews and nutrient intake recommendations. Second, repeating one of his opening statements that evidence is global, but decisions are local, he suggested that different countries convene their own expert panels to come up with nutrient intake recommendations, using the same framework and evidence base but incorporating local dietary patterns and other factors.
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From page 73... ...
with folic acid as an example, Verhagen noted that the European Food Safety Authority (EFSA) has done considerable work in the area of dietary reference values (DRVs)
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From page 75... ...
Namely, they found that it is well established that folic acid can prevent neural tube defects. It is also well established that folic acid can also mask a vitamin B12 deficiency, typically in older age.
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From page 76... ...
Verhagen emphasized that while there is a great deal of uncertainty especially around the colorectal cancer estimates shown in Table 5-1 a moderate fortification level of 70 µg would decrease the public health burden associated with folic acid intake. Additionally, he repeated that it is the scientists' job to present the evidence, but it is "at the discretion of the authorities to make a decision." In fact, the Netherlands government decided not to fortify in this case, but to supplement.
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From page 77... ...
SOURCES: Presented by Hans Verhagen, HMD Workshop, Rome, Italy, September 21, 2017 (modified with permission, European Responsible Nutrition Alliance)
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From page 78... ...
As an example of the latter, he mentioned a 2004 RIVM report on the public health burden of food safety versus an unhealthy diet (e.g., eating too many calories, eating the wrong types of foods) , where it was found that unsafe foods contribute only about 1 percent to the public health burden (van Kreijl et al., 2004)
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From page 79... ...
Verhagen agreed that, in fact, the public health burden of food safety issues, particularly those related to microbiology, can be acute. However, based on calculations that served as the basis for the van Kreijl et al.
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From page 80... ...
Rather than focusing on individual acute effects, he encouraged taking a populationbased approach when balancing the different types of outcomes. Dietary Reference Values: Considering Additional Health Benefits, Not Just Acute Effects of Deficiencies James Ntambi commented on the additional beneficial health effects of increasing nutrient intake and wondered if there is any particular nutrient recommendation that has actually yielded a beneficial effect on a global scale.
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From page 81... ...
He mentioned the very well- established evidence for the role of folic acid in neural tube defect prevention. In contrast, many authoritative bodies have concluded that there is no definitive risk of colorectal cancer, although the data indicate concern and that there should be a research agenda to establish whether or not there is a risk.
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From page 82... ...
"If the world wants to collaborate in this effort, it becomes much easier and faster," he said. Ruth Charrondiere agreed that the SRDR is a good step in a very good direction in terms of saving time and funds, as well as making systematic reviews more harmonized.
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