Effects of Inulin on the Plasma Lipid Profile of Normolipidemic and Hyperlipidemic Subjects

A Meta-analysis of Randomized Controlled Trials

Zhuang Guo; Xiao-Ming Liu; Qiu-Xiang Zhang; Feng-Wei Tian; Hao Zhang; He-Ping Zhang; Wei Chen

Disclosures

Clin Lipidology. 2012;7(2):215-222. 

In This Article

Results

Characteristics of the Studies

A flowchart on reference selection for the meta-analysis is shown in Figure 1 and the process of references selection can be found as Supplementary Material. Although two references[11,18] were published in different journals, they reported the same clinical trials, so we only included one reference in our research. In three studies[13,16,19] for which initial cholesterol and triacylglycerol values were not reported, the controls were used as basal values. In one reference,[12] although data with two time points were reported, only end points (8 weeks) for the longest duration were used. Thus, eight articles and eight randomized controlled trials were included in this meta-analysis.

Figure 1.

Flow diagram of included and excluded references relating to inulin for the treatment of hyperlipidemia.

The baseline characteristics of the included articles are presented in Table 1. Of the eight studies, four were parallel trials, three were crossover trials and one trial had a Latin square assignment. Three studies[16,17,19] included subjects with normal cholesterol concentrations, whereas five studies recruited participants with modest hypercholesterolemia. In the eight trials, data were collected from 330 subjects; the number of subjects participating in both the trial group and control group was 165. All the trials were conducted on adults in the age range 19–75 years. The studies' duration varied from 21 to 56 days, and the subjects included in the intervention group were given oral inulin from 3 to 20 g per day, which was administered in various forms, such as sweetener, vanilla ice cream, chocolate and cookies.

Serum Lipid Concentration Changes

The mean net changes between the treatment and placebo groups in terms of levels of total cholesterol, HDL-C, LDL-C and triglycerides are presented in Table 2. For the total cholesterol category, the trend towards intervention-related reduction was observed in both normolipidemic and hyperlipidemic subjects; however, only in hyperlipidemic subjects did the level of total cholesterol show a statistically significant reduction (p < 0.05) when compared with the control group (Figure 2). For normolipidemic and hyperlipidemic subjects the overall pooled estimates of the effect of inulin supplementation on total blood cholesterol were -11.97 mg/dl (-21.67–-2.28; p < 0.05) and -5.19 mg/dl (-11.53–1.14; p > 0.05), respectively. All of the trials had intervention-related trends towards a reduction in LDL-C, except for the trial reported in.[14] The meta-analyzed WMD showed a greater reduction in LDL-C while consuming an inulin-enriched diet in both hyperlipidemic (WMD: -9.60 mg/dl; p < 0.05) and all subjects recruited in this meta-analysis (WMD: -5.95 mg/dl; p < 0.05). No significant difference in serum LDL-C of normolipidemic subjects between inulin diets and control diets was observed (WMD: -0.40 mg/dl; p > 0.05) (Figure 3). Oral inulin failed to provide a significant modification of HDL-C in normolipidemic (WMD: 0.50 mg/dl; p > 0.05) and hyperlipidemic subjects (WMD: -1.13 mg/dl; p > 0.05) (Figure 4). Individual study trends for triglycerides were similar to those of total cholesterol (Figure 5). The overall results indicate a significantly greater decrease of 17.76 mg/dl in hyperlipidemic subjects (p < 0.05). The pooled mean net changes in normolipidemic and all subjects recruited in this meta-analysis with an inulin diet were -2.23 mg/dl (95% CI: -12.57–8.11; p > 0.05) and -6.82 mg/dl (95% CI: -15.49–1.86; p > 0.05).

Figure 2.

Forest plots depicting the effect of inulin on total cholesterol of normolipidemic and hyperlipidemic subjects.
WMD: Weighted mean difference.

Figure 3.

Forest plots depicting the effect of inulin on LDL-C of normolipidemic and hyperlipidemic subjects.
WMD: Weighted mean difference.

Figure 4.

Forest plots depicting the effect of inulin on HDL-C of normolipidemic and hyperlipidemic subjects.
WMD: Weighted mean difference.

Figure 5.

Forest plots depicting the effect of inulin on triglycerides of normolipidemic and hyperlipidemic subjects.
WMD: Weighted mean difference.

Publication Bias

Heterogeneity among the effect sizes of individual trials for total cholesterol, LDL-C, HDL-C and triglycerides in all subjects recruited in this meta-analysis had χ2 values of 0, 39.8, 0 and 1.9%, respectively. There was no significant heterogeneity between the studies with regard to total cholesterol (p = 0.47), LDL-C (p = 0.13), HDL-C (p = 0.94) and triglycerides (p = 0.41). Potential publication bias was examined by plotting sample size versus mean net change for total cholesterol, LDL-C, HDL-C and triglycerides for the trials included in this meta-analysis. All lipid profiles showed a typical funnel shape. Thus, there was no publication bias among the eight trials.

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