The effect of psyllium on fasting blood sugar, HbA1C, HOMA IR, and insulin control: systematic review and dose-response meta-analysis of randomized controlled trials

doi:10.21203/rs.3.rs-2812896/v1

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The effect of psyllium on fasting blood sugar, HbA1C, HOMA IR, and insulin control: systematic review and dose-response meta-analysis of randomized controlled trials

https://doi.org/10.21203/rs.3.rs-2812896/v1

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There is equivocal evidence that psyllium can prevent or attenuate increases in fasting blood sugar. Therefore, this systematic review and meta-analysis sought to investigate the influence of psyllium on hemoglobin A1C (HbA1C), fasting blood sugar (FBS), insulin, and Homeostatic Model Assessment of Insulin Resistance (HOMA IR). We searched PubMed, ISI Web of Science (WOS), and Scopus for eligible publications, up to 15 July 2022, including randomized controlled trials (RCT) assessing the effect of psyllium on HbA1C, FBS, insulin, and HOMA IR levels in adults. Using a random effects model, we report the weighted mean differences (WMD) with 95% confidence intervals (CI).In this article, 19 RCT studies, consisting of 4100 participants, were included. Psyllium significantly decreased FBS, HbA1C, and HOMA IR levels, but not insulin levels, as compared to placebo (FBS: (weighted mean difference [WMD]: -6.89; 95% CI: -10.62, -3.16; p < .001), HbA1C: (WMD: -0.75; 95% CI: -1.21, -0.29; p < .001), HOMA IR: (WMD: -1.17; 95% CI: -2.11, -0.23; p < .05), and insulin: (WMD: -2.08; 95% CI: -4.21, -0.035; p > .05)). Subgroup analyses illustrated differences in the effects of psyllium on FBS: dosages less than and more than 10 g/d showed significant differences (p value < 0.05). However, it was not significant in intervention durations less than 50 days (p value > 0.05). For HbA1C: psyllium consumption less than 10 g/d (p value > 0.05) was non-significant. For HOMA IR and insulin: no significant changes were noted with psyllium consumption less than vs. more than 10 g/d. In conclusion, we found that psyllium could significantly decrease FBS, HbA1C, and HOMA IR levels, but not insulin levels, as compared to placebo.

The global prevalence of diabetes, and in particular type 2 diabetes, is increasing. Ageing and urbanization are factors that are largely attributable for diabetes prevalence in developing countries, however, the resources for treatment are scarce (1). Hyperglycemia has been defined as a fasting blood sugar (FBS) greater than 126 mg/dL, and a random blood sugar greater than 200 mg/dL (2). Empirical evidence suggests that adequate glycemic control is associated with a reduced risk of microvascular (retinopathy, neuropathy and nephropathy) and cardiovascular toll (3, 4).

Dietary fiber has been reported to significantly lower blood sugar levels and increase insulin in people with diabetes (5). However, it has been asserted that the combination of types of fiber, i.e., dietary fiber (lignin and nondigestible carbohydrates) and functional fiber (nondigestible carbohydrates and isolated) is an important consideration (6).

Psyllium is one of the most beneficial dietary sources of fiber currently available (7), and is a gel-forming mucilage derived from the Plantago ovata seed husk (8–10). The ground skin of psyllium seeds (plantago ovata or psyllium plantago) comprises an admixture of polysaccharides, which includes hexoses, pentoses, and uronic acids, and has been used as a viscose, solvable, gel-forming non-fermented fiber supplement (11). Psyllium is typically native to India, Iran, and other Middle Eastern countries (12, 13), and the consumption of psyllium seeds has nutritional benefits including, therapeutic treatment of constipation, diarrhea, irritable bowel syndrome, inflammatory bowel disease, ulcerative colitis, colon cancer, diabetes, and hypercholesterolemia. Moreover, psyllium has been posited as a potential therapeutic option for high blood glucose levels(6–8, 11). For instance, in one study, psyllium yielded a significant decrease in hemoglobin A1C (HbA1C), as compared to the placebo group, while insulin levels remained unchanged. (14). Indeed, supplementing a moderate carbohydrate diet with psyllium, even for a short duration, appears to be capable of significantly reducing fasting plasma insulin in those living with diabetes. (15). By delaying absorption, psyllium has a comparable effect to intestinal α-glucosidase inhibitors in decreasing carbohydrates digestion and absorption, which leads to increased levels of the glucoregulatory factor glucagon-like peptide 1 (GLP-1). In turn, this ensures that vital nutrients arrive to distal regions of the small bowel (6). A lack of dietary soluble fibers in the diet has been linked to an inexorable rise of coronary heart disease, diabetes mellitus, and colon-related cancer, among other non-communicable diseases (13).

Considering the contradictory findings of studies in the field, we sought to undertake a systematic review and meta-analysis study in order to obtain a more comprehensive result. This study will investigate the effect of psyllium consumption on FBS, HbA1C, HOMA IR, and insulin in adult populations.

Search strategy and study selection

The present study was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines (16). To assess the effect of psyllium on blood sugar changes HbA1C, Homeostatic Model Assessment of Insulin Resistance (HOMA IR) and insulin, we searched for relevant studies from database inception up to 15 July 2022, across four English language databases (PubMed, Scopus, Web of Science (WOS) and Google Scholar). The data were carefully retrieved using the following keywords: ("Psyllium" OR "Plant Mucilage" OR "mucilage" OR "lunelax" OR "Metamucil" OR "ispaghul" OR "plantago" OR "isogel" OR "ispaghula" OR "psyllium-husk" OR "Plantago ovata" OR "Psyllium fiber" OR "Plantago psyllium" OR "mucilage polysaccharides") AND ("Randomized Controlled Trial" OR "Clinical Trial" OR "cluster randomized controlled trials" OR "RCTs" OR "cRCTs" OR "Controlled Clinical Trial" OR "RCT" OR "double-blind randomized controlled trial" OR "Clinical Trials as Topic" OR "clinical trial*" OR "controlled trial*" OR "intervention*" OR "Randomized" OR "Randomized" OR "randomly" OR "single-blind" OR "double-blind" OR "placebo" OR "Pilot study" OR "single-blind randomized controlled trial" OR "Controlled Clinical Trials as Topic" OR "Meta-Analysis" OR "Review" OR "Random Allocation" OR "Single-Blind Method" OR "Double-Blind Method" OR "Cross-Over Studies" OR "Comparative Study" OR "Follow-Up Studies" OR "cross-over" OR "parallel" OR "assignment" OR "trial") alone or combined together with ‘OR’ and/or ‘AND’. Reference lists of retrieved articles were interrogated for supplementary studies. To ensure accuracy, we carefully restricted our search to only include human subjects. To avoid any potential duplication, two independent researchers screened both primary titles and abstracts (Z.Gh. and Z.P.) In addition, we manually searched for additional articles in gray literature, as well as activating the alert system of Scopus and PubMed databases. For articles that we did not have access to, we emailed the corresponding author(s).

Eligibility criteria

The Population, Intervention, Comparison, Outcomes, and Study (PICOS) criteria were used for this meta-analysis study. Accordingly, adults who were over 18 years old, intervention (psyllium), comparison (placebo), outcome (alteration in FBS, HbA1C, HOMA IR and insulin levels), study design (randomized controlled trials [RCTs]) were included. The following criteria were assessed: (a) RCTs with either parallel or crossover design; (b) Adults who were ≥ 18 years; (c) evaluated the effect of psyllium on FBS, HbA1C, HOMA IR and insulin changes with a control group. Exclusion criteria were: (a) persons who were less than 18 years old; (b) in vitro, animal, or cell culture studies; (c) articles that were not RCT(d) studies that were reviews, letters, conferences, and abstracts with defective data, and seminars; (e) defective data; (f) articles without expression standard deviation (SD); (g) articles without control group; (h) articles whose study duration is less than 2 weeks. (i) Articles that were not in English and (j) Articles that had no baseline mean and SD.

Data extraction

The data extraction form was completed in both a word processor and spreadsheet by two experienced investigators, (Z.Gh. and Z.P.). All selected papers were thoroughly reviewed by the two researchers, (Z.Gh. and Z.P.). In order to obtain the full-text of the articles that we were not able to access, an email was sent to the corresponding author(s). Following successful full-text review, we extracted the following information: author’s name, the publication year, study location, design of the study (parallel or cross-over), the population of study, mean age of the participants, gender, health status of participants, sample size, psyllium dosage, duration of intervention and the mean ± SD of the FBS, HbA1C, HOMA IR, and insulin levels before and after the intervention. Studies with an additional arm will be reported as separate studies. (Table 1). When average and standard deviation were not available in numerical form, the Graph digitizer get data software was utilized to obtain the data from published figures.

Table 1

General specifications of the included studies
Author	year	Country	journal	Population	Sex	N	In_N	Pl_N	In_Mean Age	Duration (day)	Type of psyllium	Type of Pl.	Dose/day (g / day)
Ong Pui Wen et al(17)	2022	Malaysia.	http://www.japsonline.com	Healthy male adult	M	29	14	15	26	30	Psyllium husk	mixed herbs	25
Noureddin Soltanian(18)	2018	Iran	Clinical Nutrition ESPEN	patients with T2D, constipation	M/F	51	24	27	58	84	Psyllium cookie	Flaxseed and place cookie	20
Ayman S. Abutair(19)	2016	Gaza Strip	Nutrition Journal	Type 2 diabetes patients	M/F	40	18	18		56	Psyllium supp	Diet without supp	10.5
James W. Anderson(20)	1988	Lexington	Arch Intern Med	M hypercholesterolemia.	M	28	14	14	47.6	70	Psyllium Hydrophilic Mucilloid	cellulose placebo	10.2
ARRIGO F.G. CICERO(21)	2007	Italy	Clinical and Experimental Hypertension	severe hyperlipoproteinemia; uncontrolled diabetes;	M/F	96	48	48	48	180	soluble psyllium husk powder	hydrolysed guar gum	7
Arrigo F.G. Cicero(22)	2010	Italy	Mediterr J Nutr Metab	Caucasian patients	M/F	96	48	48	48	180	soluble psyllium husk powder	hydrolysed guar gum	7
Fatemeh Pourbehi(23)	2020	Iran	International Journal of Women’s Health and Reproduction Sciences	non-diabetic women with PCOS.	F	58	24	24	24	56	psyllium	microcrystalline cellulose	10
Mark N. Feinglos	2013	USA	Bioactive carbohydrates dietary fibrel	patients with type-2 diabetes mellitus	M/F	23	15	8	61.8	140	psyllium	controlled by diet and/or an oral sulfonylurea,	3.4
Mark N. Feinglos(24)	2013	USA	Bioactive carbohydrates dietary fibrel	patients with type-2 diabetes mellitus	M/F	22	14	8	64.8	140	psyllium	controlled by diet and/or an oral sulfonylurea,	6.8
Mahdieh Kamalpour(15)	2017	Iran	Journal of Dietary Supplements	Patients with Type 2 Diabetes Mellitus		37	20	17	55.9	14	psyllium powder	LoCarb	7
Johnson W. McRorie (25)	2017	USA	Nutrition Today	subject	M/F	20	10	10	56.3	90	psyllium husk	wheat dextrin	10.2
Noureddin Soltaniana(26)	2018	Iran	Complementary Therapies in Medicine	patients with type 2 diabetes and chronic constipation	M/F	51	24	27	56.8	84	Psyllium cookie	Placebo cookie	20
Rosa Solàa (27)	2010	Spain	Elsevier	CVD	M/F	187	94	93	54.24	56	Po-husk	microcrystalline-cellulose	14
G Sartore(28)	2009	Italy	European Journal of Clinical Nutrition	type II diabetes.	M/F	40	20	20	61	56	psyllium	diet alone	10.5
Seyedeh Ferdows Jazayeri(29)	2021	Iran	HindawiEvidence-Based Complementary and Alternative Medicine	NAFLD	M/F	63	31	32	43.3	84	Plantago major	toasted flour powder	4
MISAEL URIBE(30)	1985	Mexico	Gastroenterology	Hepatic Encephalopathy and Diabetes Mellitus	M/F	8	4	4		14	psyllium Plantago		35g/d fiber
Seyed Ali Ziai(14)	2005	Iran	Journal of Ethnopharmacology	diabetic patients		36	21	15	51.9	56	Psyllium	microcrystalline cellulose	10.2
Ricklefs Ka(31)	2017	USA	Obesity Medicine		M/F	17	8	9	58.5	56	ground psyllium	ground flaxseeds	9
Amjad Ali Bacha(32)	2022	Pakistan	Nutrition and Metabolic Insights	school teachers with central obesity	M/F	60	30	30	47	112	psyllium		10
N: number; In-N: intervention number; Pl-N; placebo number; IN: intervention; Pl: placebo; M: male; F: female

Quality assessment

Two investigators (Z.Gh. and Z.P.) used the Cochrane collaboration's risk of a bias assessment tool to assess the risk of bias (33). We assessed seven criteria including for each study including (a) random sequence generation, (b) allocation concealment, (c) blinding of participants and personal, (d) blinding of outcomes assessment, (e) incomplete outcome data reporting, (f) selective outcome reporting, (g) Other potential threats to validity and (h) general risk bias. So, studies were ascribed as low quality (low risk of bias for less than two domains), moderate quality (unclear risk of bias for one or two domains), and high quality (low risk of bias for all seven domains) (33) (Table 2).

Table 2

Quality assessment
Article	Random sequence generation	Allocation concealment	Blinding participant and personal	Blinding of outcome assessment	Incomplete outcome data	Selective outcome reporting	Other potential threats to validity	General risk bias
Ong Pui Wen et al	L	H	H	H	L	H	H	H
Noureddin Soltanian,	L	H	H	H	L	H	H	H
Ayman S. Abutair	L	H	H	H	L	L	H	H
James W Anderson,	H	H	L	H	L	H	L	H
ARRIGO F.G. CICERO	L	H	L	H	L	H	L	M
Arrigo F.G. Cicero	L	H	L	H	L	L	L	M
Fatemeh Pourbehi1	L	H	L	L	L	L	L	L
Mark N. Feinglos	H	H	L	L	L	H	H	H
Mark N. Feinglos	H	H	L	L	L	H	H	H
Mahdieh Kamalpour	H	H	H	H	L	H	L	H
Johnson W. McRorie Jr	L	H	H	H	L	H	H	H
Noureddin Soltaniana	L	H	H	H	H	H	H	H
Rosa Solàa	L	H	L	H	L	L	L	M
Seyedeh Ferdows Jazayeri	L	L	L	H	L	H	H	M
Amane Sheikh1	L	H	H	H	L	H	H	H
MISAEL URIBE	L	H	H	H	L	H	H	H
Seyed Ali Ziai	L	H	L	H	L	L	H	H
Ricklefs Ka	L	H	H	H	L	L	L	H
Amjad Ali Bacha	L	H	H	H	L	H	H	H
L: low
H: high
M: medium

Data synthesis and statistical analysis

We sought to assess changes in FBS, HbA1C, HOMA IR, and insulin levels, as calculated from the mean changes and Standard Deviations (SD) using a random-effects model (34). To accurately measure pooled prevalence estimates with 95% confidence intervals, we utilized a random effects model and Comprehensive Meta-Analysis (CMA) software to assess the degree of heterogeneity between studies. An I² value of more than 50% was used to infer a high level of heterogeneity and may be used as an indication that the random effects model should be applied. To address the sources of heterogeneity, we separately performed meta-regression and subgroup analyses. Meta-regression was used for the dosage of psyllium and duration of studies. In all statistical analyses, the significance level was considered as P-value < 0.05, and the meta-analysis was conducted using CMA version 3. If the SD of the mean difference was not available in the published studies, we used this formula: SD change = square root ([SD baseline]² + [SD final]² – [2R × SD baseline × SD final]) (35). For calculating SD from SE, we used the following formula: SD = SE \({*}\sqrt{{n}}\). When there was no information in the form of average and standard deviation, but it was reported in the form of a graph, the get data Graph digitizer software was used to extract the information. For considering heterogeneity, we used the I square (I²) index. Accordingly, (I² < 25%), (I² = 25–50%), (I² = 50–75%), and (I² > 75%) were considered low, moderate, severe, and highly heterogeneous, respectively (36). We performed pre-defined subgroup analyses based on the baseline FBS, HbA1C, HOMA IR, and insulin levels, psyllium dosage (mg/d), study duration (weeks), persons’ mean age, sample size, health status, sensitivity analysis, and publication bias

Search results

This study is registered in PROSPERO, under code CRD42023385375. The flowchart of the procedure of screening and study selection is displayed in Fig. 1. The alert notification in PubMed and Scopus was activated to avoid missing potentially relevant paper. We removed 2334 duplicate articles (2070) and subsequently reviewed the titles and abstracts (2160). Next, 160 full-text articles were screened. We excluded 141 studies, where 42 studies were not related, 5 studies did not have a control group, 2 studies worked on animals, 2 studies had no baseline mean and SD, 5 studies did not work on adults, 6 studies were not written in English, 2 studies were not RCT's, and 4 studies had no SD. Therefore, 19 RCTs were entered in the final meta-analysis. (Fig. 1)

Study characteristics

The 19 eligible studies were published from 1985 to 2022 and were 14–182 days in duration. The total number of participants was 4100 (1640 cases and 2018 controls). General characteristics of these studies are shown in Table 1. These studies were conducted in different countries (Malaysia, Iran, Gaza Strip, Lexington, Italy, USA, Spain, Mexico, Pakistan). The mean age of participants ranged between 24 and 77.2 years, with most studies conducted in both genders. The dosages of psyllium utilized in the included studies ranged from 0.002–25 g/day.

Meta-analysis results

A total of 19 studies, including 4100 individuals (1640 cases and 2018 controls), examined the effects of psyllium supplementation on changes in FBS, HbA1C, HOMA IR and insulin levels. We used a random-effects model, which indicated a significant decrease in FBS, HbA1C, and HOMA IR levels, and a non-significant decrease in insulin levels, compared to the placebo FBS: (weighted mean difference [WMD]: -6.89; 95% CI: -10.62, -3.16; p < .001) (Fig. 2), HbA1C: (WMD: -0.75; 95% CI: -1.21, -0.29; p < .001) (Fig. 3 ), HOMA IR: (WMD: -1.17; 95% CI: -2.11, -0.23; p < .05) (Fig. 4) and insulin: (WMD: -2.08; 95% CI: -4.21, -0.035; p > .05) ( Fig. 5). However, significant heterogeneity was noted for FBS: (I² = 82.04%, p < .001); HbA1C :(I² = 73.10%, p < .001), HOMA IR: (I² = 87.27%, p < .001), and insulin: (I² = 83.75%, p < .001). The sensitivity analysis showed that the sequential deletion of each study did impact FBS: (WMD altered between − 4.49 and − 8.72), and HbA1C: (WMD altered between − 0.62 and − 0.89), but did yield changes for two studies in HOMA IR: (WMD altered between − 1.49 and − 0.48) and seven studies in insulin: (WMD altered between − 2.75 and − 0.77).

Subgroup analysis

We stratified studies based on baseline FBS, HbA1C, HOMA IR, and insulin levels (mean ± SD), psyllium dosage (g/d), study duration (days), and participants' BMI. These analyses did not show any source of heterogeneity. Subgroup analyses illustrated diversities in the effects of psyllium on FBS: dosage subgroup with psyllium consumption less than vs. more than 10 g/d it showed significant difference for FBS (p value < 0.05). However, it was not significant when intervention duration was less than 50 days duration (p value > 0.05), HbA1C was not significant at dosages less than 10 g/d (p value > 0.05). HOMA IR and insulin were not significant at dosages less than and more than 10 g/d (p value > 0.05), respectively. The results of the subgroup analyses are summarized in (Table 3).

Table 3

subgroups analysis
Variable	dose		duration
Variable	< 10g /day	> 10 g/day	< 50 day		> 50day
FBS
Number of comparisons	7	12	3	16
WMD (95% CI)	-8.96(-13.67, -4.24)	-3.97(-4.80, -3.15)	-1.03(-8.26, 6.19)	-8.01(-12.16, -3.87)
P-value	0.00	0.00	0.77	0.00
I squared	69.93	87.02	32.35	85.59
p- heterogeneity	0.00	0.00	0.22	0.00
Insulin
Number of comparisons	4	5
WMD (95% CI)	-0.81(-3.57, 1.94)	-3.26(-7.85, 1.33)
P-value	0.56	0.16
I squared	82.11	91.89
p- heterogeneity	0.00	0.00
HbA1C
Number of comparisons	4	5
WMD (95% CI)	-0.32(-0.73, 0.09)	-1.37(-2.03, -0.71)
P-value	0.12	0.00
I squared	70.09	38.74
p- heterogeneity	0.01	0.16
HOMA IR
Number of comparisons	4	4
WMD (95% CI)	-0.88(-2.41, 0.63)	-1.50(-3.25, 0.24)
P-value	0.25	0.09
I squared	87.89	95.80
p- heterogeneity	0.00	0.00
FBS: fasting blood glucose; WMD: weighted mean difference

Dose–response analysis

Psyllium dosage and duration had a no significant effect on FBS, HOMA IR and insulin; but duration was significant for of HbA1C. (Fig. 6–9). The results of the meta regression analyses are shown in Table 4.

Table 4

meta regression
variable	Slop	95% CI	P-value
FBS
Dose	0.12	-0.56, 0.80	0.72
duration	-0.07	-0.15, 0.01	0.09
Insulin
Dose	-0.21	-0.59, 0.15	0.24
duration	-0.00	-0.03, 0.02	0.75
HbA1C
Dose	-0.07	-0.15, 0.00	0.08
duration	0.00	0.00, 0.01	0.00
HOMA IR
Dose	-0.02	-0.58, 0.54	0.94
duration	-0.00	-0.02, 0.00	0.33
FBS: fasting blood glucose; HbA1C: hemoglobin A1C; HOMA IR: Homeostatic Model Assessment of Insulin Resistance; CI: confidence interval

Publication bias

The assessment of publication bias is illustrated in plots. The Egger's test indicated no evidence of publication bias in studies examining the effect of psyllium on FBS (p = 0.19). HbA1C (p = 0.19), HOMA IR (p = 0.24), and insulin (p = 0.40). The results of the publication bias analysis are shown in Table 5.

Table 5

publication bias
variable	Corrected effect size			Begg				Egger						Fail safe n test
variable	Study trimmed	WMD	CI 95%	KENDALL TAU		Z value	P-value 2 tailed	intercept	CI95%	T value		Df	P-value	n
FBS	0	-6.89	-10.62, -3.16	-0.26	1.60		0.10	-0.89	-2.30, 0.51	1.33	17.00		0.19	320.00
Insulin	0	-2.08	-4.21, 0.03	-0.17	0.62		0.53	-1.27	-4.67, 2.12	0.88	7.00		0.40	34.00
HbA1C	0	-0.75	-1.21, -0.29	-0.13	0.52		0.60	-1.61	-4.25, 1.02	1.44	7.00		0.19	78.00
HOMA IR	0	-1.17	-2.11, -0.23	-0.37	1.23		0.21	-2.15	-6.28, 1.96	1.27	6.00		0.24	73.00
FBS: fasting blood glucose; HbA1C: hemoglobin A1C; HOMA IR: Homeostatic Model Assessment of Insulin Resistance; CI: confidence interval; WMD: weighted mean difference

This systematic review and meta-analysis highlighted that a significant decrease in FBS, HbA1C, and HOMA IR levels, and non-significant decrease in insulin levels, was evident following psyllium consumption, vs. placebo. However, despite these findings, a significant amount of heterogeneity was indicated for FBS, HbA1C, HOMA IR, and insulin. The sensitivity analysis we conducted indicated no significant effect from the removal of single studies for FBS and HbA1C. However, the removal of two studies in HOMA IR and seven studies in insulin were significant. We categorized studies based on baseline FBS, HbA1C, HOMA IR, and insulin levels (mean ± SD), psyllium dosage (g/d), study duration (days), and participants' BMI. Further subgroup analyses illustrated diversities in the effects of psyllium on FBS, HbA1C, HOMA IR, and insulin levels. For instance, in dosages less and more than 10 g/d, and intervention durations less than 50 days, were influential. For HbA1C, it was not significant in dosages less than 10 g/d. For HOMA IR and insulin, results were not significant in dosages less and more than 10 g/d, respectively. In dose–response analysis, psyllium dosage and duration appeared to be linearly related to FBS, HOMA IR, and insulin, however, this was only significant for HbA1C.- Additionally, there was no publication bias evident in studies examining the effect of psyllium on FBS levels, HbA1C, HOMA IR, and insulin.

Previously, Xiao et al reported that a significant reduction in FBS and HbA1c, which are indicators of glucose control, could be seen after supplementation with psyllium. Indeed, in the aforementioned study, the authors noted six studies, with 124 and 112 participants in the psyllium and control group, respectively, with overall results yielding a significant reduction in FBS levels and HbA1c (37). Indeed, similar findings were reported in Gibb et al (2015), where the authors reported that postprandial blood glucose levels were significantly reduced (6). Nevertheless, discrepant results have been reported across the literature; for instance, a randomized controlled trial on the impact of psyllium supplementation resulted in no significant effect on FBS vs. a carbohydrate reduction regimen (15). However, with regards to Kamalpour et al, the lack of change reported may be attributable to the relatively short intervention period, i.e., two weeks (15). Nevertheless, the authors did note a significant reduction in TNF-α and fasting plasma insulin, which have both been posited as mediators in numerous diabetes-associated complications (38, 39).

It has previously been suggested that consumption of psyllium before meals can significantly reduce fasting blood glucose levels and HbA1c levels (6). Indeed, psyllium may be able to improve or manage glycemic control (37). The mechanism of action for the reduction in blood sugar in patients with diabetes for psyllium is comparable to other soluble fibers. For instance, soluble fiber can result in a reduction in sugar absorption, which can, consequently, attenuate metabolic syndrome severity in diabetic patients. Psyllium may slow intestinal transit time and lead to an increased feeling of satiety, in addition to decreasing blood sugar and insulin requirements. The viscosity of soluble fiber is responsible for the slower absorption of macronutrients, and protection against digestive enzymes. Additionally, soluble fiber coats the intestinal surface, which prevents the passage of nutrients (19, 40–42). Furthermore, consumption of foods with adequate fiber content elicits a lower insulin response and lower blood glucose levels. Indeed, psyllium can provoke changes in intestinal hormones and a subsequent reduction of glucose after meals (41).

Strengths and limitations

This study has several strengths that should be acknowledged: (a) this was, to our knowledge, the first meta-analysis evaluating the effect of psyllium on fasting blood glucose, HbA1C, HOMA IR, and insulin; (b) we performed predefined subgroup analyses to identify sources of between-study heterogeneity; (c) we also performed a detailed sensitivity analysis. However, concomitant to the noted strengths, there are limitations that should be considered in the interpretation of our findings. For instance: (a) we restricted number of the included studies; (b) some of the included studies did not account the dietary intake, which is known to potentially affect blood glucose, HbA1C, HOMA IR, and insulin; (c) we had unidentified heterogeneity in several of the results; (d) the age range of included participants was wide.

This systematic review and meta-analysis sought to investigate the influence of psyllium on HbA1C, fasting blood sugar (FBS), insulin, and Homeostatic Model Assessment of Insulin Resistance (HOMA IR), owing to the equivocal results in the extant literature. Accordingly, we found that psyllium could significantly decrease FBS, HbA1C, and HOMA IR levels, but not insulin levels, as compared to placebo. Therefore, we advocate that psyllium be considered as a potential treatment option, if clinically appropriate.

Ethics approval and consent to participate

It has received prior approval from the Medical Ethics Committee of Isfahan University of Medical Sciences, with an ethics code of IR.MUI.RESEARCH.REC.1401.396. This study is registered in PROSPERO, under code CRD42023385375.

Consent for publication

Not applicable

Availability of Data and Material (ADM)

The datasets generated and/or analyzed during the current study are not publicly available due to some restrictions applied by ethics committee; but are available from the corresponding author on reasonable request

Competing interests

The authors affirm that they do not possess any identifiable financial interests or personal affiliations that could have potentially influenced the research presented in this manuscript.

Funding

Present study has been financially supported by a grant from Isfahan University of Medical Sciences, (Code: IR.MUI.RESEARCH.REC.1401.396, Grant number: 1401332).

Authors' contributions

All authors have read and approved the manuscript; Z.Gh: The role of the author of the article in designing the research study, collecting the article data, analyzing and interpreting the article data. The active role of the author in writing the article and approving the final version of the article. Taking on the general and common responsibilities of the article about the research and the article

Z.P.: Preparing a draft of the article, or revising and revising it carefully

C.C.: revising and revising it carefully

Acknowledgment

The authors express their gratitude to the Student Research Committee at Isfahan University of Medical Sciences for providing financial support for this study. This research was conducted with the aid of a grant from the same committee (grant number: 1401332).

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No competing interests reported.

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The effect of psyllium on fasting blood sugar, HbA1C, HOMA IR, and insulin control: systematic review and dose-response meta-analysis of randomized controlled trials

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Abstract

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Introduction

Method

Search strategy and study selection

Eligibility criteria

Data extraction

Quality assessment

Data synthesis and statistical analysis

Results

Search results

Study characteristics

Meta-analysis results

Subgroup analysis

Dose–response analysis

Publication bias

Discussion

Strengths and limitations

Conclusion

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References

Additional Declarations

Supplementary Files

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Version 1