Table 4.
Overview of methodology employed in the report development
| Authority/Reference | Carbohydrate exposures | Health outcomes | Quality assessment of individual included studies | Judging the strength of the evidence | |
|---|---|---|---|---|---|
| Type of review | Grading system | ||||
| Australian National Health and Medical Research Council (NHMRC) 2013 [4] | Food-based exposures only, including the following main carbohydrate-providing foods: • Sugars • Fruit • Dairy • Cereals/Grains • Legumes • Nuts and seeds • Beverages Glycaemic index and glycaemic load of the diet |
• Obesity • Cardiovascular disease • Stroke • Diabetes/Insulin resistance • Cancer • Hypertension • Eye-health • Bone health • Dental health • Mental health |
Y (level of evidence according to NHMRC scheme) | • Systematic reviews (for carbohydrate-specific exposure−outcome relations) | • Grade A (convincing association) • Grade B (probable association) • Grade C (suggestive association) • Grade D (weak evidence) |
| EFSA 2010 [12] | • Total and glycaemic carbohydrates • Sugars • Dietary fibre • Glycaemic index and glycaemic load |
Varies by exposure • Body weight • Glucose tolerance and insulin sensitivity • Type 2 diabetes mellitus • Serum lipids • Blood pressure • Cardiovascular disease • Gastrointestinal function • Dental caries • Colorectal cancer |
N | • Narrative review | None |
| German Nutrition Society (DGE) 2012 [7] | • Total carbohydrates • Mono-saccharides and disaccharides (sugar), sugar-sweetened beverages • Polysaccharides • Dietary fibre/whole-grain products • Glycaemic index and glycaemic load |
• Obesity • Type 2 diabetes mellitus • Dyslipoproteinaemia • Hypertension • Metabolic syndrome • Coronary heart disease • Cancer |
Y (level of evidence according to WHO scheme) | • Systematic review | • Convincing • Probable • Possible • Insufficient (acc. to WHO scheme) |
| Health Council of the Netherlands. Background Document Methodology for the evaluation of the evidence for the Dutch dietary guidelines 2015 [18] | Nutrients • Digestible carbohydrates • Dietary fibre Foods and beverages (including the following main carbohydrate-providing foods): • Fruit • Cereals/cereal products • Legumes • Nuts and seeds • Dairy products • Potatoes • Beverages with added sugar |
• Coronary heart disease • Stroke • Heart failure • Diabetes mellitus type 2 • Chronic obstructive pulmonary disease • Breast, colorectal and lung cancer • Dementia • Depression • Additional consideration (based on RCTs only) • Blood pressure • LDL-cholesterol • Body weight |
Limited quality check, using inclusion/exclusion criteria for studies to be considered only | • Systematic review of RCT’s and cohort studies | Conclusions in four categories: 1: statement on effect/association + strength of evidence 2: effect /association unlikely 3: effect /association ambiguous 4: too few studies In deriving the guidelines for a healthy diet, the committee gives most weight to the effects and links with strong evidence. |
| Nordic Nutrition Recommendations (NNR) 2012 [8] |
• Total and glycaemic carbohydrates • Glycaemic index and glycaemic load • Added sugars • Dietary fibre |
Varies by exposure • Body weight • Plasma lipids, glucose and insulin • Type 2 diabetes • Blood pressure • CVD • Laxation • Colonic fermentation • Dental caries • Pregnancy outcomes • Cancer |
Y a (Quality Assessment tool addressing study design, population characteristics, exposure and outcome measure) | Systematic reviews sugar intake macronutrients food and weigh maintenance Narrative reviews for dietary fibre and glycaemic index |
• Convincing • Probable • Limited – suggestive • Limited – no conclusion (modified from WCRF) |
| Scientific Advisory Committee on Nutrition SACN (UK) 2015 [9] |
• Total carbohydrates • Sugars and sugars-sweetened foods and beverages • Starch and starch-rich foods • Dietary fibre • Non-digestible oligosaccharides, resistant starch, polyols and polydextrose • Glycaemic index and glycaemic load |
• Cardio-metabolic health: - cardiovascular disease - hyperlipdaemias and blood lipids - incident hypertension and blood pressure - vascular function - markers of inflammation - diabetes and glycaemia - obesity - energy intake and eating motivation • Colo-rectal health - colo-rectal cancer - irritable bowel syndrome - constipation • Oral health |
Y (limited quality check) | • Meta-analysis (if 3 studies of similar design) including assessment of heterogeneity • Systematic review |
• Adequate • Moderate • Limited (according to specifically developed scheme and expert judgement) |
| US 2010 [10] | Specific questions formulated for different carbohydrate exposures including the following: • Dietary fibre • Whole grain intake • Vegetable and fruits (not including juice) • Glycaemic index (GI) /glycaemic load (GL) • Sugar sweetened beverages (SSB) (in relation to energy intake and body weight only) |
Specific questions formulated for different outcomes including the following: • Energy intake (for exposure SSB only) • Satiety • Measures of adiposity • Type 2 diabetes • Cardiovascular disease • Cardiovascular outcomes (for exposure vegetables and fruits only) • Cancer (for exposures GI/GL only) |
Y (NEL quality rating to indicate the extent to which the design and conduct of a study is shown to be protected from systematic bias, non-systematic bias, and inferential error) | • Systematic review for all outcome – exposure relations except for health benefits of dietary fibre (answered using 2002 DRI Report and 2008 ADA position paper) | 2010 DGAC grading system considers five elements of relevance to scoring systematics: (1) quality (scientific rigor and validity; study design and execution), (2) consistency (consistency of findings across studies), (3) quantity (number of studies; numbers per study), (4) impact (importance of studied outcomes; magnitude of effect) and (5) generalizability to population of interest. Levels of grading: • Strong • Moderate • Limited • Expert opinion only • Grade not assignable |
| US 2015 [26] | • Added sugars intake | • Body weight/obesity • Type 2 diabetes • Dental caries • Cardiovascular disease |
Y • Risk of bias assessment: NEL Bias Assessment Tool • AMSTAR Quality Assessment for systematic reviews or meta-analyses |
• Systematic review only for CVD outcome • Other outcomes: narrative review of WHO reviews and/or systematic reviews and meta-analyses |
2015 DGAC grading system considers five elements of relevance to scoring systematics 1) Quality (Scientific rigor and validity; Study design and execution), 2) Consistency (Consistency of findings across studies), 3) Quantity (Number of studies; Numbers per study), 4) Impact (Importance of studied outcomes; Magnitude of effect) and 5) Generalizability to population of interest based on risk of bias, consistency, quantity, impact and generalizability: Levels of grading: • Strong • Moderate • Limited • Expert opinion only • Grade not assignable |
| WHO/FAO Expert Consultation 2003 [14] | • Free sugars (frequency and amount) • Sugar-free chewing gum • Non-starch polysaccharides (dietary fibre) • Starch • Wholegrain cereals • Low glycaemic index foods |
• Excess weight gain and obesity • Diabetes • Cardiovascular diseases • Cancer • Dental diseases • Osteoporosis |
N | • Narrative review | • Convincing • Probable • Possible • Insufficient (modified from WCRF) |
| WHO 2015 [2] | • Total sugars • Free sugars • Added sugars • % En from sugars • Sugar-sweetened beverages • Fruit juices |
• Body weight or fatness gain measured by - weight change, BMI - body fatness and distribution • Dental caries (not erosion) |
Y (Cochrane criteria for RCT, own scheme for quality of cohort studies) | • Meta-analyses published in peer-reviewed journals • GRADE Evidence profiles for - Effect of free sugars intake reduction - Effect of free sugars intake increase - Effect of decreasing free sugars intake <10 %En/<5 %En |
GRADE system: Quality of evidence • High • Moderate • Low • Very low |