Table 2.
The description and characteristics of included studies (adapted from Ojo et al. [20]).
| Authors/Country of Study | Type of Study | Details of Sample | Mean Age/Range (Years) | Aim | Type of Interventions | Findings |
|---|---|---|---|---|---|---|
| Birkeland et al. [37], Norway |
RCT | n = 25 | 63.1: 41–73 | To examine the effect of inulin-type fructans on faecal microbiota and short chain fatty acids in patients with type 2 diabetes. | Inulin-type fructans (a mixture of oligofructose and inulin) versus placebo (maltodextrin) A 4 week washout separated 6 weeks of treatment |
The results found a moderate potential of inulin-type fructans to promote the composition of gut microbiota and to increase microbial fermentation in T2D. |
| Candela et al. [38], Italy |
RCT | Ma-Pi 2 diet (n = 21), control diet (n = 19) |
66 | Two different energy-restricted dietary approaches were explored, i.e., the fibre-rich macrobiotic Ma-Pi 2 diet or a control diet | Macrobiotic Ma-Pi 2 diet rich in fibre versus control diet. A 21-day treatment |
The Ma-Pi 2 diet was effective in alleviating the increase of possible proinflammatory groups, in the gut ecosystem, but not the control diet. It demonstrated the possibility of reversing proinflammatory dysbiosis in patients with T2D and its effectiveness in improving metabolic control. |
| Gonai et al. [36], Japan |
RCT | GOS (n = 27), placebo (n = 25) |
GOS (55 ± 11) Placebo (54 ± 12) |
To evaluate the role of GOS on glycaemic control, gut microbiota, and metabolites in patients with type 2 diabetes. | GOS versus placebo (maltodextrin) A 4-week treatment |
Bifidobacteriaceae was significantly restored in patients with diabetes after consuming GOS. On the other hand, there was no improvement in LBP and glucose tolerance during this short period of trial. It was shown that GOS could mitigate dysbiosis in patients with diabetes, and continuous intake of GOS may be useful in managing type 2 diabetes. |
| Hiel et al. [33], Belgium |
RCT | 47 Metformin-treated participants (all diabetic, prebiotic n = 24, placebo n = 23) | Age ranged from 18 to 65 years. | To explore the effect of inulin supplementation with metformin in obese patients with T2D and their beneficial effects through modulation of gut microbiota. | Subjects were randomly assigned to the prebiotic or placebo arm A 3-month treatment |
A large increase in Bifidobacterium may be due to inulin intake rather than a driver of prebiotic-linked biological outcomes. |
| Medina-Vera et al. [28], Mexico |
RCT | T2D (n = 81) Final Group numbers analysed: DF (n = 28), placebo (n = 25) |
DP (50.4 ± 8.7) Placebo (49.8 ± 10.6) |
To examine the role of dietary intervention (functional food-based) on faecal microbiota and biochemical parameters in patients with type 2 diabetes. | A dietary portfolio (DP) versus placebo A 3-month treatment |
The long term use of diets that are high in fibre, rich in polyphenol and vegetable-protein-based provide advantages in enhancing the faecal microbiota composition and may be used as therapies for managing dyslipidaemia and inflammation. |
| Pedersen et al. [29], UK |
RCT | GOS (n = 14), placebo (n = 15) |
GOS (56.7 ± 1.6) Placebo (58.1 ± 1.7) |
To compare the effects of prebiotic supplementation with placebo treatment in patients with type 2 diabetes. | GOS versus placebo (maltodextrin) A 12-week treatment |
As compared with the placebo, supplementation with prebiotic fibre did not appear to show any significant impact on clinical outcomes or bacterial abundances. |
| Reimer et al. [34], Canada |
RCT | PGX® (n = 147), placebo (n = 143) |
PGX® (56.2 ± 8.6) Placebo (53.4 ± 9.9) |
To evaluate the adjunct effect of the soluble viscous fibre PGX® on glycemic control in patients with T2D. | PGX® versus placebo A 52-week treatment. |
PGX® may be a useful adjunct to weight loss programs in patients with type 2 diabetes based on improvements in other metabolic parameters. |
| Soare et al. [39], Italy |
RCT | Ma-Pi 2 diet (n = 25), control diet (n = 26) |
Ma-Pi 2 diet (67 ± 8.163) Control diet (65 ± 7.284) |
The effect of various dietary methods (the macrobiotic Ma-Pi 2 diet) were compared with standard diets recommended for patients with type 2 diabetes. | Fibre-rich macrobiotic Ma-Pi 2 diet versus control diet A 21-day treatment |
There was significantly better improvements in metabolic control in patients with type 2 diabetes following the intervention with a short-term Ma-Pi 2 diet. |
| Soare et al. [40], Italy |
RCT | Ma-Pi 2 diet (n = 25), control diet (n = 26) |
Age ranged from 40 to 75 years | To investigate the effects of macrobiotic Ma-Pi 2 diet versus a standard recommended diet (control diet) on inflammatory markers in patients with T2D. | This was a post hoc analysis of the MADIAB trial A 21-day RCT. |
As compared with the baseline data, it was found that Ma-Pi 2 diet was a safe dietary method of reducing levels of inflammatory markers, in the short term. |
| Soare et al. [41], Italy |
RCT | Ma-Pi 2 diet (n = 17), control diet (n = 23) |
Ma-Pi 2 diet (65 ± 8.89) Control diet (64 ± 8.15) |
Evaluation of the advantages of the original 21-day intensive dietary interventions beyond the original MADIAB trial duration and into everyday life. | Fibre-rich macrobiotic Ma-Pi 2 diet versus control diet A 6-month follow-up study |
There was higher percentage reduction in body weight and a higher percentage increase in LDL cholesterol in the Ma-Pi diet. Furthermore, all the participants’ total and LDL cholesterol levels were within recommended levels. |
| Zhao et al. [35], China |
RCT | High dietary fibre (n = 27), control (n =16) |
High dietary fibre (58.4 ± 6.2) Control (59.7 ± 6.0) |
To assess the effect of gut microbiota and its role in glucose homeostasis in patients with type 2 diabetes. | High dietary fibre versus usual care A 84 days study |
Dietary fibre was effective in promoting a group of SCFA-producing strains, while most of the other potential producers were either reduced or unchanged in patients with type 2 diabetes. |
Abbreviations: DP (dietary portfolio); GOS (galacto-oligosaccharide); LBP (lipopolysaccharide binding protein); LDL (low density lipoprotein) cholesterol; Ma-Pi 2 (macrobiotic diet); PGX® (PolyGlycopleX®); SCFA (short chain fatty acid); T2D (type 2 diabetes); RCT (randomised Controlled Trial).