Table 1.
Summary of included studies
| Study ID, country of origin and setting | Details of sample | Details of intervention and study design | Assessment timepoints | Primary outcomes | Secondary outcomes |
|---|---|---|---|---|---|
| Sheth et al [35] India Diabetes healthcare clinic |
n = 35 (treatment arm n = 25, control arm n = 10) Male: NR Mean age (SD): NR Time since diagnosis: NR Management of T2DM: NR |
RCT 1 g synbiotic product (two species of Lactobacillus and Bifidobacterium each, one species of Streptococcus and yeast, and 300 mg oligosaccharide) taken daily with meals |
Baseline and 21 days | Glycaemic control: FBG, PP2BS, HbA1c | Gut microbiota, SCFAs (butyrate, propionate) |
| Candela et al [32] Italy University endocrinology and diabetes department |
n = 40 (additional 13 non-T2DM at baseline; T2DM participants: treatment arm n = 21, control arm n = 19 included in analysis) Male: 50% Mean age (SD): 58 (16) years Time since diagnosis: NR Management of T2DM: Diet and/or hypoglycaemic drugs for 6 months prior to study |
Controlled open-label trial Ma-Pi 2 diet (detailed in [37]) |
Baseline and 21 days | FBG, PP2BS | HbA1c, total cholesterol, LDL-cholesterol and HDL-cholesterol, CRP, TNF-α, IL-6, anthropometrics, gut microbiota |
| Balfegó et al [29] Spain Hospital clinic, Barcelona |
n = 35 (treatment arm n = 19, control arm n = 16) Male: 44% Mean age (SD): 61 (1) years Time since diagnosis: NR Management of T2DM: diet only |
Pilot randomised trial Standard T2DM with 100 g sardines on 5 days/week for 6 months |
Baseline and 6 months | Glycaemic control: FBG, FBI, HbA1c, HOMA-IR | TNF-α, IL-6, IL-8, IL-10, total adiponectin, anthropometrics, nutritional intake |
| Firouzi et al [33] Malaysia Teaching hospital |
n = 136 (treatment arm n = 68, control arm n = 68) Male: 52.2% Mean age (SD): 54 (8) years Time since diagnosis: NR Management of T2DM: oral glucose-lowering drugs |
Randomised, double-blind, parallel-group, placebo-controlled trial Probiotics containing 3×1010 viable microbial strains twice per day: three strains of Lactobacillus (Lactobacillus acidophilus, Lactobacillus casei and Lactobacillus lactis) and three strains of Bifidobacterium (Bifidobacterium bifidum, Bifidobacterium longum and Bifidobacterium infantis); contains 1010 CFU |
Baseline and weeks 6 and 12 | Glycaemic control: FBG, FBI, HbA1c, HOMA-IR and QUICKI | Anthropometrics, lipid profile, BP, CRP, gut microbiota |
| Pedersen et al [34] UK General practitioners (Surrey) |
n = 29 (treatment arm n = 14, control arm n = 15) Male: 100% Mean age (SD): 57 (2) years Time since diagnosis: NR Management of T2DM: Metformin, n = 10 Metformin and gliclazide, n = 5 Metformin and sitagliptin, n = 3 Metformin, gliclazide and sitagliptin, n = 1 Metformin, sitagliptin and thiazolidinedione, n = 1 Gliclazide and sitagliptin, n = 2 Gliclazide, n = 1 |
Randomised, double-blind, parallel-group, placebo-controlled trial. 5.5 g prebiotic fibre Galacto-oligosaccharide (detailed in [38]) |
Baseline and 12 weeks | Intestinal permeability, endotoxemia and glycaemic control: FBG, FBI, HbA1c, HOMA-IR and C-peptide | Gut microbiota, lipid profile, BP, anthropometrics, CRP, TNF-α, IL-6 |
| Kim et al [36] Republic of Korea Diabetes healthcare clinic |
n = 6 (n = 4 with type 2 diabetes, all included in analysis) Male: 17% Mean age (SD): 60 (12) years Time since diagnosis: NR Management of T2DM: NR |
Single-group study Strict vegetarian diet containing 16% protein, 72% carbohydrates (42 g fibre/day) and 12% fat |
Baseline and days 3, 5, 7, 14, 21 and 28 | FBG | Gut microbiota, 2 hfs OGTT, HbA1c, weight, BMI, faecal lipocalin-2, total SCFA, acetate, propionate, butyrate |
| Sasaki et al [30] Japan Outpatient diabetes clinic |
n = 66 (treatment arm 300 mg n = 23, 900 mg n = 22, control arm n = 21) Male: 58% Mean age (SD): 62 (9) years Time since diagnosis: NR Management of T2DM: Insulin injection, n = 12 Metformin, n = 18 Insulin secretagogue, n = 38 α-Glucosidase inhibitor, n = 31 PPAR-γ antagonist, n = 17 |
RCT Two doses of transglucosidase totalling 300 or 900 mg/day |
Baseline and 12 weeks | HbA1c | Gut microbiota, FBG, insulin, BMI, nutritional intake |
| Andreasen et al [31] Denmark General practitioners |
n = 48 (24 with T2DM; all participants included in analysis: treatment arm n = 24, control arm n = 24) Male: 100% Mean age (SD): 62 (8.9) years Time since diagnosis: NR Management of T2DM: Metformin, n = 9 Sulfonylurea, n = 3 Glitazones, n = 1, Statins, n = 5 |
RCT 1 g probiotic capsule/day containing 1010 CFU Lactobacillus acidophilus NCFM |
Baseline and 4 weeks | Gut microbiota | FBG, HbA1c, BMI, 2 hfs OGTT, HOMA-IR, FBI, TNF-α, IL-6, IL-1RA, CRP |
CFU, colony-forming units; FBG, fasting blood glucose; FBI, fasting blood insulin; NR, not reported; PP2BS, postprandial blood glucose; T2DM, type 2 diabetes mellitus