Table 1 Numbers of papers remaining after each stage of the selection process of the systematic review

Raw hits from all sources

Number of studies reviewed for inclusion criteria after reading the title

Number of studies excluded because: administration was not oral

of pharmacological interventions

they did not report the result of a clinical trial

clinical trials were not randomised

results already reported in another paper (duplicate reports)

Number of RCTs found during the reviewing process by serendipity and added to the review

Number of RCTs matching inclusion criteria and reviewed here

Number of negative RCTs that concerned nutritional intervention for which no positive RCT was found

Number of RCTs the quality of which was scored (Table 3)