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Degrees of evidence by the Joint WHO/FAO Expert ConsultationIn the Joint WHO/FAO Expert Consultation, scientific evidence has been categorized into four different levels of strength depending on the number and type of studies carried out and the consistency of the results: "Convincing evidence Evidence based on epidemiological studies showing consistent associations between exposure and disease, with little or no evidence to the contrary. The available evidence is based on a substantial number of studies including prospective observational studies and where relevant, randomized controlled trials of sufficient size, duration and quality showing consistent effects. The association should be biologically plausible. Probable evidence. Evidence based on epidemiological studies showing fairly consistent associations between exposure and disease, but where there are perceived shortcomings in the available evidence or some evidence to the contrary, which precludes a more definite judgement. Shortcomings in the evidence may be any of the following: insufficient duration of trials (or studies); insufficient trials (or studies) available; inadequate sample sizes; incomplete follow-up. Laboratory evidence is usually supportive. Again, the association should be biologically plausible. Possible evidence. Evidence based mainly on findings from case-control and cross-sectional studies. Insufficient randomized controlled trials, observational studies or non-randomized controlled trials are available. Evidence based on non-epidemiological studies, such as clinical and laboratory investigations, is supportive. More trials are required to support the tentative associations, which should also be biologically plausible. Insufficient evidence. Evidence based on findings of a few studies which are suggestive, but are insufficient to establish an association between exposure and disease. Limited or no evidence is available from randomized controlled trials. More well designed research is required to support the tentative associations. The strength of evidence linking dietary and lifestyle factors to the risk of developing obesity, type 2 diabetes, CVD [cardiovascular diseases], cancer, dental diseases, osteoporosis, graded according to the above categories, is summarized in tabular form, and attached to this report as an Annex [seewww.who.int/nutrition/topics/annex/en/index.html Source & © WHODiet, Nutrition and the prevention of chronic diseases (2003), Chapter 5 Population nutrient intake goals for preventing diet-related chronic diseases, 5.1 Overall goals, 5.1.2 Strength of evidence Related publication:
Other Figures & Tables on this publication: Table 1: Global and regional per capita food consumption (kcal per capita per day) Table 2. Vegetable and animal sources of energy in the diet (kcal per capita per day) Table 4. Per capita consumption of livestock products Table 6. Ranges of population nutrient intake goals Table 8: Classification of overweight in adults according to BMIa Table 9: Summary of strength of evidence on lifestyle factors and risk of developing type 2 diabetes Table 11: Summary of strength of evidence on lifestyle factors and the risk of developing cancer Table 13: Prevalence of toothlessness (edentulousness) in older people throughout the world Table 14: Summary of strength of evidence linking diet to dental caries Table 15: Summary of strength of evidence linking diet to dental erosion Table 16: Summary of strength of evidence linking diet to enamel developmental defects Table 17: Summary of strength of evidence linking diet to periodontal disease Table 18: Summary of strength of evidence linking diet to osteoporotic fractures Figure 3: Trends in the supply of vegetables, by region, 1970-2000 Figure 4: Ranges of population nutrient intake goals Figure 2. Calories from major commodities in developing countries Degrees of evidence by the Joint WHO/FAO Expert Consultation |
