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Cited by 149Fatty Acid Research and HealthNutritional Studies and DietDiet and metabolism studies

Effects of Monounsaturated Fatty Acids on Glycaemic Control in Patients with Abnormal Glucose Metabolism: A Systematic Review and Meta-Analysis

Schwingshackl, L., Strasser, B., Hoffmann, G.·2011·Annals of Nutrition and Metabolism
DOI 10.1159/000331214
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Abstract

Background/Aims: In 2008, the American Diabetes Association recommended low-carbohydrate or low-fat diets for weight management in patients with established type 2 diabetes (T2D), while the amount of monounsaturated fatty acids (MUFA) was not specified. This systematic review focused on the effects of diets high in MUFA versus diets low in MUFA on important risk factors of T2D (i.e. plasma glucose, insulin, homeostasis model assessment of insulin resistance and glycosylated haemoglobin, HbA1c). Methods: Nine randomized controlled intervention trials with a total of 1,547 participants and a running time of at least 6 months, comparing diets high versus low in MUFA among adults with abnormal glucose metabolism (T2D, impaired glucose tolerance and insulin resistant), being overweight or obese, have been included in the meta-analysis. We performed a random effects meta-analysis to determine the weighted mean differences with 95% confidence intervals using the software package Review Manager 5.0.25 of the Cochrane Collaboration. Results: Significant differences in HbA1c were found (weighted mean difference –0.21%, 95% CI –0.40 to –0.02; p = 0.03), favouring the high MUFA groups. In contrast, fasting plasma glucose, fasting plasma insulin as well as the homeostasis model assessment of insulin resistance were not affected by the amounts of MUFA in the dietary protocols. Conclusions: In summary, this systematic review found that high MUFA diets appear to be effective in reducing HbA1c, and therefore, should be recommended in the dietary regimes of T2D.

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Written from the paper’s full text.

TL;DR

This systematic review and meta-analysis of 9 long-term RCTs in people with abnormal glucose metabolism found that high-MUFA diets (≥12% of total energy) significantly lowered HbA1c compared with low-MUFA diets. Fasting plasma glucose, fasting insulin, and HOMA-IR did not differ significantly between high- and low-MUFA diets.

Key findings

  • HbA1c was significantly reduced with high- vs low-MUFA diets: WMD −0.21% (95% CI −0.40 to −0.02; p = 0.03; 5 studies, 667 participants; I² = 15%). The high-MUFA vs low-fat subgroup also showed a significant reduction: WMD −0.28% (95% CI −0.52 to −0.03; p = 0.03).
  • Fasting plasma glucose did not differ significantly: WMD −3.02 mg/dl (95% CI −6.66 to 0.63; p = 0.11; 9 studies, 1,545 participants; I² = 81%).
  • Fasting plasma insulin did not differ significantly: WMD −0.05 (95% CI −1.60 to 1.49; p = 0.94; 9 studies, 1,547 participants; I² = 84%).
  • HOMA-IR did not differ significantly: WMD −0.26 (95% CI −0.75 to 0.24; p = 0.31; 6 studies, 1,355 participants; I² = 86%).

Methods

  • Systematic review and meta-analysis of RCTs in participants with abnormal glucose metabolism (IGT, T2D, IR), BMI ≥25, intervention/follow-up ≥6 months, and nutritional counselling by a dietician. Searches covered Medline (1966–May 2011), Embase (1980–May 2011), and the Cochrane Trial Register (until May 2011).
  • Included 9 RCTs with 1,547 participants; intervention durations ranged from 6 months to 4 years. High-MUFA diets were defined as ≥12% of total energy content (TEC); low-MUFA diets as ≤12% TEC, including low-fat, low/high glycaemic index, high-protein, and control diets.
  • Random-effects meta-analysis using Review Manager 5.0.25; outcomes were fasting plasma glucose, fasting plasma insulin, HOMA-IR, and HbA1c. Results reported as weighted mean differences (WMDs) with 95% CIs; heterogeneity assessed with Q and I²; funnel plots assessed publication bias; Jadad score assessed study quality.

Limitations

  • Stated: unpublished data were not considered; included publications varied in diet types, MUFA definitions, study populations, intervention time, and follow-up protocols; drug regimens were not identical across participants; mixed IGT, IR, and T2D populations were included, and effects might be especially strong in T2D. The funnel plot for HbA1c showed little asymmetry/small potential publication bias.
  • Evident: heterogeneity was substantial for fasting plasma glucose, fasting plasma insulin, and HOMA-IR (I² >80%), so those pooled null estimates should be interpreted cautiously; the significant HbA1c finding rests on 5 studies and 667 participants.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1159/000331214

Cites

41 of 41 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

0 of 29 cited sources checked · 0 supported · 0 flagged

  • Findingown data

    High-MUFA diets compared with low-MUFA diets do not significantly affect fasting plasma glucose in patients with abnormal glucose metabolism (WMD -3.02 mg/dl, 95% CI -6.66 to 0.63; p=0.11).

    “The pooled estimates of effects of high-versus low-MUFA diets on fasting plasma glucose were -3.02 mg/dl, which was statistically not significant (95% CI -6.66 to 0.63; p = 0.11).”
    • Also stated in: § Abstract · plain
      “fasting plasma glucose, fasting plasma insulin as well as the homeostasis model assessment of insulin resistance were not affected by the amounts of MUFA in the dietary protocols.”
    Quote in the paperNot a substantial claim
    • The authors state this as an assumption: Imputing the baseline standard deviation for one trial is a valid procedure because baseline and post-intervention standard deviations were similar in the other included trials.
  • Findingown data

    High-MUFA diets compared with low-MUFA diets do not significantly affect HOMA-IR in patients with abnormal glucose metabolism (WMD -0.26, 95% CI -0.75 to 0.24; p=0.31).

    “Decreases in HOMA-IR did not differ significantly between high-and low-MUFA dietary protocols (WMD -0.26, 95% CI -0.75 to 0.24; p = 0.31).”
    • Also stated in: § Abstract · plain
      “fasting plasma glucose, fasting plasma insulin as well as the homeostasis model assessment of insulin resistance were not affected by the amounts of MUFA in the dietary protocols.”
    Quote in the paperNot a substantial claim
    • The authors state this as an assumption: Imputing the baseline standard deviation for one trial is a valid procedure because baseline and post-intervention standard deviations were similar in the other included trials.
  • Findingown data

    In post-hoc analysis, high-MUFA diets compared with low-fat (LF) diets significantly reduce HbA1c in patients with abnormal glucose metabolism (WMD -0.28%, 95% CI -0.52 to -0.03; p=0.03).

    “The post-hoc analyses showed that the HbA1c reduction was significant following a high-MUFA as compared to LF diets (WMD -0.28%, 95% CI -0.52 to -0.03; p = 0.03) ( fig. 1 ).”
    Quote in the paperSubstantial claim
    • The authors state this as an assumption: Imputing the baseline standard deviation for one trial is a valid procedure because baseline and post-intervention standard deviations were similar in the other included trials.
  • Findingown data

    High-MUFA diets compared with low-MUFA diets do not significantly affect fasting plasma insulin in patients with abnormal glucose metabolism (WMD -0.05 mg/dl, 95% CI -1.60 to 1.49; p=0.94).

    “Fasting insulin was assessed in a total of 1,547 subjects.WMD for the effects of high-versus low-MUFA regimens was -0.05 mg/dl (95% CI -1.60 to 1.49; p = 0.94), which was not statistically significant.”
    • Also stated in: § Abstract · plain
      “fasting plasma glucose, fasting plasma insulin as well as the homeostasis model assessment of insulin resistance were not affected by the amounts of MUFA in the dietary protocols.”
    Quote in the paperNot a substantial claim
    • The authors state this as an assumption: Imputing the baseline standard deviation for one trial is a valid procedure because baseline and post-intervention standard deviations were similar in the other included trials.
  • Findingown data

    Heterogeneity across trials for fasting plasma glucose, fasting plasma insulin, and HOMA-IR was substantial (I2 >80%).

    “However, we found heterogeneity across trials concerning fasting plasma glucose, fasting plasma insulin and HOMA-IR (I 2 1 80%).”
    Quote in the paperNot a substantial claim
  • May combine two claims. 12
  • Classified as probably not a substantial claim. 17

  • May combine two claims.

    Findingown data

    The funnel plot for HbA1c response to high-MUFA diets indicates little asymmetry, suggesting a small potential publication bias.

    “The funnel plot with respect to effect size changes for HbA1c response to high-MUFA diets indicates little asymmetry, suggesting that there might be a small potential publication bias ( fig. 2 ).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    The funnel plot for HbA1c response to high-MUFA diets shows a small asymmetry, indicating a reduced risk of publication bias.

    “The funnel plot to effect size changes for HbA1c response to high-MUFA diets shows a small asymmetry, which indicates a reduced risk of publication bias.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Kinsell et al. reported that the type of fat consumed might influence insulin action in humans.

    “Kinsell et al. [10] reported that the type of fat consumed might influence insulin action in humans.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [10] source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    The improvement in insulin resistance might have beneficial effects, not only on glucose control, but also on cardiovascular disease in patients with T2D.

    “The improvement in IR might have beneficial effects, not only on glucose control, but also on CVD in patients with T2D [7] .”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [7] source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Previous meta-analyses comparing diets with different amounts of fats reported an inconclusive impact of MUFA on biomarkers of cardiovascular disease, possibly because they included short-term intervention trials.

    “Previous meta-analyses, comparing diets with different amounts of fats in daily nutrition, reported an inconclusive impact of MUFA on biomarkers of CVD, which might be due to the fact that these meta-analyses included short-term intervention trials [12,13] .”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [12] source

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    • cites [13] source

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  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    Attrition rates did not differ significantly between the intervention groups.

    “Attrition rates did not differ significantly between the intervention groups.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    In a retrospective study by Currie et al., HbA1c values >6.5% were correlated with an increased mortality rate in patients with diabetes.

    “In a retrospective study by Currie et al. [31] , investigating 47,970 patients with diabetes, HbA1c values 1 6.5% were correlated with an increased mortality rate.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [31]

      Not checked in the free run.

  • Classified as probably not a substantial claim. May combine two claims.

    Premisecitation

    Dietary composition could play a significant role in improving insulin sensitivity and reducing the risk of T2D as well as its associated complications.

    “Dietary composition could play a significant role in improving insulin sensitivity and reducing the risk of T2D as well as its associated complications [5] .”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [5] source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Interpretationnone given

    The effects of the intervention on glucose parameters might be especially strong in patients with T2D.

    “Subjects with IGT, IR as well as with T2D were included, and the effects of the intervention on glucose parameters might be especially strong in patients with T2D.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductreasoning

    The literature chosen for the present analysis varies regarding type(s) of diets used, definitions of MUFA diets, study population, intervention time, and long-term follow-up protocols.

    “Therefore, it is not surprising that the literature chosen for the present analysis varies regarding type(s) of diets used, definitions of MUFA diets, study population, intervention time as well as long-term followup protocols.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Study design and conductnone given

    This systematic review does not consider unpublished data, and unpublished data may have had at least a moderate impact on the effect size estimates.

    “This systematic review does not consider unpublished data, and it cannot be excluded that these results may have had at least a moderate impact on the effect size estimates.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    The drug regimen was not identical for all participants in the included studies.

    “In addition, the drug regimen was not identical for all participants in the included studies.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    A meta-analysis of observational studies showed that chronic hyperglycaemia is associated with an increased risk of cardiovascular disease in persons with T2D.

    “A meta-analysis of observational studies showed that chronic hyperglycaemia is associated with an increased risk of CVD in persons with T2D [9] .”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [9] source

      Not checked in the free run.

  • Classified as probably not a substantial claim. May combine two claims.

    Premisecitation

    The meta-analysis of short-term trials showed that a high-MUFA diet had more favourable effects on glucose control in T2D than low-MUFA diets, while no effects on fasting insulin were observed.

    “The outcome of this analysis shows that a high-MUFA diet had more favourable effects on glucose control in T2D than low-MUFA diets, while no effects on fasting insulin had been observed [12] .”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [12] source

      Not checked in the free run.

  • Classified as probably not a substantial claim.

    Study design and conductreasoning

    The random-effects model was used to estimate WMDs with 95% confidence intervals to consider heterogeneity.

    “To consider heterogeneity, the random-effects model was used to estimate WMDs with 95% confidence intervals (CIs).”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    In the Framingham Heart Study, impaired fasting glucose was associated with increased coronary heart disease risk in women.

    “In the Framingham Heart Study, impaired fasting glucose was associated with increased coronary heart disease risk in women [8] .”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [8] source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Long-term intervention trials have demonstrated a significant correlation between substantial weight loss or increased physical activity and a reduced incidence of T2D.

    “Long-term inter-vention trials have demonstrated a significant correlation between substantial weight loss or increased physical activity and a reduced incidence of T2D [3,4] .”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [3] source

      Not checked in the free run.

    • cites [4] source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    Funnel plots were used to assess potential publication bias.

    “Funnel plots were used to assess potential publication bias (i.e. the tendency for studies that yield statistically significant results to be more likely to be submitted and accepted for publication).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    Esposito et al. reported significant improvements in adiponectin levels in the high-MUFA group compared with an LF protocol after a 4-year intervention period, with a simultaneous reduction in the need for antihyperglycaemic medication in the high-MUFA group.

    “Esposito et al. [18] reported significant improvements in adiponectin levels in the high-MUFA group, compared with an LF protocol after a 4-year intervention period with a simultaneous reduction in the need for antihyperglycaemic medication in the high-MUFA group.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [18] source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    An HbA1c increase of 1 percentage point was associated with a relative risk for death from any cause of 1.24 in men and 1.28 in women.

    “Likewise, an HbA1c increase of 1 percentage point was associated with a relative risk for death from any cause of 1.24 in men and 1.28 in women [32] .”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [32]

      Not checked in the free run.

  • May combine two claims.

    Interpretationcitation

    MUFA-based dietary strategies might provide cardiovascular benefits to persons at risk, by limiting lipid and insulin excursions, and may thereby contribute to optimal glycaemic control after meal challenges.

    “These data suggest that MUFA-based dietary strategies might provide cardiovascular benefits to persons at risk, by limiting lipid and insulin excursions, and may thereby contribute to optimal glycaemic control after meal challenges.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    High levels of adiponectin have been shown to be associated with a reduced risk of T2D.

    “In addition, high levels of adiponectin have been shown to be associated with a reduced risk of T2D [38] .”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [38]

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Specific recommendations for MUFA are given by the American Heart Association (<15% of TEC) and by the American Dietetic Association (>20% of TEC), but not by the American Diabetes Association.

    “Specific recommendations for MUFA are given by the American Heart Association ( ^ 15% of TEC) and by the American Dietetic Association ( ! 20% of TEC) [40,41] , but not by the American Diabetes Association [11] .”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites [40]

      Not checked in the free run.

    • cites [41]

      Not checked in the free run.

    • cites [11] source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Gillingham et al. concluded that more and more epidemiological and human clinical trial data demonstrate the cardioprotective activity of the MUFA content of dietary fat.

    “In a recently published review, Gillingham et al. [39] concluded that more and more epidemiological and human clinical trial data demonstrate the cardioprotective activity of the MUFA content of dietary fat.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [39]

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    The beneficial effect of dietary MUFA on insulin sensitivity is associated with a conserved IRS-1/PI3 kinase insulin signalling pathway, which was altered by saturated fatty acids.

    “The authors concluded that the beneficial effect of dietary MUFA on insulin sensitivity is associated with a conserved IRS-1/PI3 kinase insulin signalling pathway, which was altered by saturated fatty acids [37] .”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [37]

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Early pancreatic β-cell dysfunction causes insulin resistance and impaired glucose tolerance.

    “Early pancreatic ␤ -cell dysfunction causes IR and IGT [33,34] .”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [33]

      Not checked in the free run.

    • cites [34]

      Not checked in the free run.

26 of 26

  • The authors state this as an assumption.

    Imputing the baseline standard deviation for one trial is a valid procedure because baseline and post-intervention standard deviations were similar in the other included trials.

    “We assumed that this is a valid procedure, since the baseline and post-intervention SD were found to be similar within the other trials included in the metaanalysis.”
1 of 1

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • Table describes change scores, but methods specify endpoint values

    Major

    Table 2 says its pooled effects are changes from baseline, whereas the methods say the meta-analysis compared post-intervention values. These are different outcome measures.

  • Esposito citation points to a different author

    Minor

    The discussion identifies reference [18] as an Esposito study, but entry 18 in the reference list is by Boulé and colleagues.

  • Fasting insulin is reported in incompatible units

    Minor

    The assessed-outcomes section specifies U/ml for fasting plasma insulin, but the fasting-insulin result reports its mean difference in mg/dl.

3 of 3

Cites

Flagged first, then by citations

Research works printed but not linked: 1

  1. 10.1007%2fs00125-003-1190-9 · DOI · Paper page

Cited by

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Related

Authors
Schwingshackl, L., Strasser, B., & Hoffmann, G.
Affiliations
UMIT TIROL - Private University for Health Sciences and Health Technology (AT)
ORCID
Venue
Annals of Nutrition and Metabolism
Publisher
S. Karger AG
Published
2011
Volume
58
Issue
4
Pages
290-296
ISSN
  • 0250-6807 (ISSN-L)
  • 1421-9697
DOI
10.1159/000331214
OpenAlex
W1973429542
Semantic Scholar
daac3f77ce897816a7166330a66056e99aa7339f
Cited by
147
References
41
Citations by year
2026: 3 · 2025: 3 · 2024: 7 · 2023: 14 · 2022: 9 · 2021: 18 · 2020: 13 · 2019: 8 · 2018: 11 · 2017: 7 · 2016: 14 · 2015: 11 · 2014: 13 · 2013: 9 · 2012: 6
FWCI
1.12
Type
journal article
Language
en
Open access
closed
Licence
Locations
  • Annals of Nutrition and Metabolism (publishedVersion)
  • PubMed (publishedVersion)
Topics
  • Health Sciences › Nursing › Nutrition and Dietetics › Fatty Acid Research and Health
  • Health Sciences › Medicine › Public Health, Environmental and Occupational Health › Nutritional Studies and Diet
  • Health Sciences › Medicine › Physiology › Diet and metabolism studies
Keywords
monounsaturated fatty acids, glycemic control, type 2 diabetes, impaired glucose tolerance, insulin resistance, HbA1c, fasting blood glucose, fasting insulin, dietary fat composition, abnormal glucose metabolism, obesity
MeSH terms
Adult, Diabetes Mellitus, Type 2, Fatty Acids, Monounsaturated, Glycated Hemoglobin, Humans, Hyperglycemia, Hypoglycemia, Insulin Resistance, Randomized Controlled Trials as Topic, Practice Guidelines as Topic, Glucose Intolerance, Overweight

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