Carbohydrates and Health

• Limited – three to four cohort studies were identified and there was some
indication that the results were in the same direction but no meta-analysis was
performed. However, the evidence may also have been considered limited if
there were a number of studies, but the biological plausibility was unclear or
the methodology was not precise or the exposures were heterogeneous.
Randomised controlled trials
A2.19 Generally, there needed to be three or more randomised controlled trials to
determine if there was evidence of an effect or not. Expert judgement was used
to determine if the quality of these data permitted a conclusion to be drawn.
Where an effect appeared to be present, the evidence was graded as adequate,
moderate or limited. The number of studies was used as an approximate guide
only, since issues surrounding study design, study size, methodology and definition
of exposures affected the final grading of the evidence.
A2.20 Evidence was graded as follows:
• Adequate – a meta-analysis was performed on three or more randomised
controlled trials. Alternatively, a total of four or more studies were identified in
the systematic review and/or the update search; these consistently showed the
same outcome although a meta-analysis was not performed.
• Moderate – a meta-analysis was performed on three or more randomised
controlled trials. Alternatively, three or more randomised controlled trials were
identified in the systematic review and/or the update search, which consistently
showed the same outcome although a meta-analysis was not performed.
• Limited – three to four randomised controlled trials were identified and there
was some indication that the results were in the same direction, but no metaanalysis
was performed. However, the evidence may also have been considered
limited if there were a number of studies, but the biological plausibility was
unclear, the methodology was not precise or the exposures were heterogeneous.
A2.21 The evidence was normally considered as insufficient where there were fewer than
three studies of the same type. Alternatively, if there were more studies but they
were of poor quality, the evidence may have also been considered as insufficient.
A2.22 Evidence was deemed inconsistent according to statistical considerations i.e.
in a meta-analysis, when I 2 >75%, the confidence intervals did not overlap or if
the results of individual studies were not in the same direction. When the I 2 was
greater than 75%, but the forest plot suggested there was evidence of a direction
for an outcome, expert judgement was used to upgrade the conclusion, where
appropriate.
A2.23 In addition to the evidence grading, if an effect or association was shown,
statements have been provided on the following:
• Whether the effect or association indicated beneficial or adverse effects with
higher intakes of carbohydrate or carbohydrate components.
206