Table 1.

Criteria of PECOS standards for articles selection.

Standards	Inclusion	Exclusion
Population	Human, 0–70 years, with or without diabetes associated complication or other diseases.	Animal studies, pregnant, lactating, celiac, probiotic and prebiotic use, use medication affect gut microbiota like metformin, use antibiotic during the last 3 months, unusual eating habits (vegans).
Exposure	T1D more than 1 year	Prediabetic subjects with islet autoimmunity or not diagnosed with T1D or T1D <1 year
Control	Healthy subjects
Outcome	Gut microbiota composition, glycemic indices (HbA1c, blood glucose level, time in range).	Poor procedure, unclear results, or other results.
Study design	Observational studies (cohort, case–control).	Interventional studies