Eligibility criteria

The PECOS framework, as defined by Sargeant and O'Connor [5], was used to define the review eligibility criteria, as follows. The population was all human populations, with no limitations by age or other participant characteristics, location, or context/settings. The exposures were all foods (e.g. hamburger, leafy greens); we neither considered drinking water (tap, bottled, or other), breastfeeding, nor nasogastric feeding as foods, nor did we include studies that assessed general nutrition (including malnutrition) as a risk factor for STEC infection. The comparator group was individuals who are not ill with STEC infection (i.e. controls; determined either via laboratory testing or by the absence of symptoms) and the outcome was sporadic illness caused by laboratory-confirmed STEC infection. The study design was case-control studies and thus the effect measure of interest was the OR.