• Increase Font Size
  • Decrease Font Size
  • View as PDF

Disorders of Lipid Metabolism and Nuts

Citation:
 
Study Design:
Class:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:

To review 18 well-controlled studies testing the hypothesis that monounsaturated fatty acid (MUFA) calories are superior to carbohydrate calories as a substitute for saturated fatty acid (SFA) calories.

Inclusion Criteria:

Not described.

Exclusion Criteria:

Not described.

Description of Study Protocol:

 

18 well controlled studies (3-12 weeks in length) compared the effects of substituting MUFA calories for SFA instead of carbohydrate.

Sources of MUFA in diet:

Olive oil

Canola oil

Nuts

Legumes

  • ­ MUFA and low fat, low carbohydrate diets provided a range of SFA (4-12% energy) and cholesterol (<100-410 mg/day).
  • ­ MUFA diets were higher in total fat (33-55% energy) compared to low fat, ­ high carbohydrate diets (18-30% energy).
  • ­ MUFA diets provided 17-33% energy from MUFA, while low fat, ­ high carbohydrate diets provided 55-67% energy from carbohydrate.
Data Collection Summary:

 

Outcome measures:

  • Percent change in serum lipids from baseline
    • Total cholesterol
    • LDL-cholesterol
    • HDL-cholesterol
    • Triglycerides.
Description of Actual Data Sample:
  • 18 clinical studies (3-12 weeks in length) compared the effects of substituting MUFA calories for SFA instead of carbohydrate.
    • Nine studies included only men
    • Three studies included only women
    • Six included both men and women.
Summary of Results:

 

Serum lipid changes on low fat, high ­ carbohydrate diets (range):

  • Total cholesterol: –16.6% to + 2.5%
  • LDL-cholesterol: -19.7% to + 0.8%
  • TG: -23.4% to +37.3%
  • HDL-cholesterol: -25.2% to +1.8%.

­ Serum lipid changes on MUFA diets (range):

  • Total cholesterol: -20.4% to –2.8%
  • LDL-cholesterol: -21.6% to –2.2%
  • TG: -42.7% to +11.9%
  • HDL-cholesterol: -9.0% to + 6.0%.
Author Conclusion:

High MUFA, low-SFA diets are equally as effective as low-fat, low-SFA, high carbohydrate diets in reducing total and LDL-cholesterol and have the added benefits of a greater magnitude of TG lowering and maintaining HDL levels in patients who do not require weight loss.

 

Funding Source:
University/Hospital: Nutrition Department, The Pennsylvania State University
Reviewer Comments:

 

A meta-analysis of this research is needed to evaluate the consistency and strength of these results.

This review did not report whether studies used RCT or cohort or other designs. Most studies had a small sample size.

An important point made in the introduction of this article:

Step I diet: low LDL-cholesterol 7% to 9%.

Step II diet: low LDL-cholesterol 10% to 20%.

No information was provided regarding the following: inclusion criteria, search strategy, study design for each clinical trial, characteristics of participants other than gender, quality assessment of studies, variation in study results, limitations.

Quality Criteria Checklist: Review Articles
Relevance Questions
  1. Will the answer if true, have a direct bearing on the health of patients? Yes
  2. Is the outcome or topic something that patients/clients/population groups would care about? Yes
  3. Is the problem addressed in the review one that is relevant to dietetics practice? Yes
  4. Will the information, if true, require a change in practice? Yes
 
Validity Questions
  1. Was the question for the review clearly focused and appropriate? Yes
  2. Was the search strategy used to locate relevant studies comprehensive? Were the databases searched and the search termsused described? No
  3. Were explicit methods used to select studies to include in the review? Were inclusion/exclusion criteria specified andappropriate? Wereselectionmethods unbiased? No
  4. Was there an appraisal of the quality and validity of studies included in the review? Were appraisal methodsspecified,appropriate, andreproducible? No
  5. Were specific treatments/interventions/exposures described? Were treatments similar enough to be combined? No
  6. Was the outcome of interest clearly indicated? Were other potential harms and benefits considered? Yes
  7. Were processes for data abstraction, synthesis, and analysis described? Were they applied consistently acrossstudies and groups? Was thereappropriate use of qualitative and/or quantitative synthesis? Was variation in findings among studies analyzed? Were heterogeneity issued considered? If data from studies were aggregated for meta-analysis, was the procedure described? No
  8. Are the results clearly presented in narrative and/or quantitative terms? If summary statistics are used, are levels ofsignificance and/or confidence intervals included? Yes
  9. Are conclusions supported by results with biases and limitations taken into consideration? Are limitations ofthe review identified anddiscussed? No
  10. Was bias due to the review's funding or sponsorship unlikely? Yes