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Database of Abstracts of Reviews of Effects (DARE): Quality-assessed Reviews [Internet]. York (UK): Centre for Reviews and Dissemination (UK); 1995-.

Database of Abstracts of Reviews of Effects (DARE): Quality-assessed Reviews [Internet].

Effect of diacylglycerol on postprandial serum triacylglycerol concentration: a meta-analysis

T Xu, X Li, X Ma, Z Zhang, T Zhang, and D Li.

Review published: 2009.

Link to full article: [Journal publisher]

CRD summary

This review concluded that diacylglycerol reduced the serum triaglycerol concentrations at two, four and six hours postprandially compared to triaglycerol and was positively correlated with daily dosage. The first, but not the second conclusion reflected the results of the review. The review suffered from a number of problems and neither conclusion can be regarded as reliable.

Authors' objectives

To compare the effect of diacylglycerol on postprandial serum triaglycerol concentration with that of triaglycerol.


MEDLINE (from 1966), EMBASE (from 1984) and The Cochrane Library (from 2006) were searched up to 2007. References of identified papers were checked. Only studies reported in English and published in full were eligible for inclusion.

Study selection

Randomised controlled trials (RCTs) that assessed diacylglycerol alone compared with triaglycerol and reported postprandial serum triaglycerol concentration were eligible for inclusion.

Included studies enrolled patients who were healthy, had or did not have impaired glucose tolerance, had insulin sensitivity or insulin resistance or had type 2 diabetes. The great majority of participants were male. Mean age ranged from 26 to 62 years. Mean body mass index ranged from 21 to 27. Daily doses of diacylglycerol ranged from 10g/day to 44g/day, where reported. All trials had a crossover design. Washout periods ranged from one week to one month.

The authors stated neither how the papers were selected for the review nor how many reviewers performed the selection.

Assessment of study quality

The authors did not state that they assessed validity, although information on blinding of trials was extracted.

Data extraction

Data were extracted on the mean and standard deviation or standard error for the change in serum triaglycerol concentration from baseline at all postprandial time points. Two reviewers independently performed the data extraction; differences were resolved through discussion with a third reviewer. Authors were contacted for missing information; where necessary missing standard deviations were imputed from other data and values were calculated from graphs.

Methods of synthesis

The trials were combined in a random-effects meta analysis to calculate a weighted mean difference (WMD) with 95% confidence interval (CI) for each time point. Statistical heterogeneity between studies was assessed using the Χ2 and I2 statistics; where there was no evidence of statistical heterogeneity, a fixed-effect model was presented. Trials with multiple arms had data included in the analysis as though each comparison were an independent study. A sensitivity analysis was used to assess the influence of studies where standard deviations had been imputed or data calculated from graphs. Regression analysis was used to investigate the impact of dose on efficacy. Subgroup analysis was used to compare the effect of treatment on groups with and without impaired glucose tolerance. Publication bias was assessed by visual inspection of funnel plots and the failsafe N was calculated.

Results of the review

Seven RCTs (n=151) were included in the review. All trials were double-blinded.

There was a statistically significantly smaller increase in triaglycerol concentration in the diacylglycerol groups at two hours (WMD -0.07 mmol/L, 95% CI -0.13 to 0.00mmol/L, p=0.05; seven RCTs, nine comparisons). There were statistically significant differences at four hours (WMD -0.15mmol/L, 95% CI -0.24 to -0.06 mmol/L, p=0.002; seven RCTs, 10 comparisons) and at six hours (WMD -0.14mmol/L, 95% CI -0.23 to -0.05mmol/L, p=0.002; four RCTs, six comparisons). There was no statistically significant difference between the groups: in initial fasting serum triaglycerol concentration (five RCTs); in concentrations at 30 minutes and one hour postprandially (one RCT in each case); at three hours (three RCTs); and at eight hours (two RCTs). There was no evidence of statistically significant heterogeneity between studies in any analysis.

Results of subgroup analyses for patients with and without impaired glucose tolerance were reported for each time interval, as was the linear regression that investigated the impact of daily dosage. There were some indications of publication bias for some analyses, although funnel plots are difficult to interpret with so few studies

Authors' conclusions

Diacylglycerol reduced the postprandial serum triaglycerol concentrations at two, four and six hours postprandially compared to triaglycerol and was positively correlated with daily dosage.

CRD commentary

The review question and the inclusion criteria were clear. The authors searched three relevant databases, but the decision to limit the review to published studies reported in English may have increased the chances of publication and language biases. The authors reported that they used methods designed to reduce reviewer bias and error in the extraction of data, but not in the selection of studies. They did not report that they conducted a validity assessment, which made it difficult to determine the reliability of the evidence represented by the included studies. The decision to employ meta-analysis appeared reasonable and heterogeneity was assessed appropriately. Where trials contained multiple arms, the comparisons were treated as independent trials. The techniques used to incorporate the multiple arms into the meta-analyses were not described; it was likely that the power of these trials was over-represented as a result and the correlation between comparisons was excluded from consideration. The authors used a number of techniques to explore differences between studies and comparisons; these were reasonable, but the conclusion they drew from the dose-response analyses did not represent the lack of statistically significant correlations in the review. This review had a number of problems, which included: limited eligibility that may have resulted in publication bias; no validity assessment; inappropriate synthesis techniques and conclusions that did not reflect the results of the analysis. The conclusions cannot be regarded as reliable.

Implications of the review for practice and research

The authors did not state any implications for practice or further research.


Not stated.

Bibliographic details

Xu T, Li X, Ma X, Zhang Z, Zhang T, Li D. Effect of diacylglycerol on postprandial serum triacylglycerol concentration: a meta-analysis. Lipids 2009; 44(2): 161-168. [PubMed: 18989717]

Indexing Status

Subject indexing assigned by NLM


Adult; Diglycerides /administration & dosage /pharmacology; Female; Humans; Male; Middle Aged; Postprandial Period; Time Factors; Triglycerides /blood



Database entry date


Record Status

This is a critical abstract of a systematic review that meets the criteria for inclusion on DARE. Each critical abstract contains a brief summary of the review methods, results and conclusions followed by a detailed critical assessment on the reliability of the review and the conclusions drawn.

CRD has determined that this article meets the DARE scientific quality criteria for a systematic review.

Copyright © 2014 University of York.

PMID: 18989717