Table 2.

Population, Intervention/Exposure, Comparator, Outcomes, Timing, Setting and Study designs (PI/ECOTSS) criteria for the papers to be included in the systematic review

Population	Intervention/exposure	Comparator	Outcomes	Timing	Setting	Study design
(1) Children (0–18 years) (2) Young adults (18–35 years) non-pregnant/non-lactating (3) Pregnant women (4) Lactating women (5) Older adults (≥65 years) (6) Vegetarians, including vegans	B12 intake, supplemental and dietary	Different levels of exposure	B12 status: *s/p-B12 *s/p-HOLO-TC *s/p-MMA *s/p-tHcy *Combined indicators *Breastmilk B12 (relevant in infants)	RCTs ≥4 weeks, cohorts ≥12 months	Relevant for the general population in the Nordic and Baltic countries	RCTs, cohort studies, case-control studies, case cohort studies and cross-sectional studies (only for limited periods as pregnancy and lactation)