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DLM: Major Dietary Components for LDL-Cholesterol Reduction (2001)

Citation:

Howell WH, McNamara DJ, Tosca MA, Smith BT, Gaines JA. Plasma lipid and lipoprotein responses to dietary fat and cholesterol: meta-analysis. Am J Clin Nutr. 1997; 65:1747 1764.

Worksheet created prior to Spring 2004 using earlier ADA research analysis template.
 
Study Design:
Cross-Sectional Study
Class:
D - Click here for explanation of classification scheme.
Quality Rating:
Negative NEGATIVE: See Quality Criteria Checklist below.
Research Purpose:
Inclusion Criteria:
  1. women
  2. black men
  3. white men with imputed data
  4. subjects taking meds to lower serum cholesterol
  5. subjects with questionable data.
Exclusion Criteria:
Description of Study Protocol:

Data collected:

  1. Weight (paper gowns and foam rubber slippers)
  2. Height with rubber slippers
  3. 24-hour recalls
  4. blood samples for serum lipids.

Data analyzed by BMI and age.

BMI categories:
  • < 21
  • 21.1 to 23
  • 23.1 to 25
  • 25.1 to 27
  • 27.1 to 30
  • >30

Age categories:
  • 20-44 years
  • 45-59 years
  • 60-74 years
Data Collection Summary:

NHANES II conducted from 1976 through 1980, a representative sample of civilian, noninstitutionalized residents of the US

Outcome measures:

  1. BMI
  2. serum lipids
Description of Actual Data Sample:

Summary of Results:

4834 white men had total cholesterol values.

85% had HDL cholesterol values

2846 had fasting serum TG values

1837 men had data for TG and 83% of those had data for calculating LDL cholesterol

Using linear trend analysis, changes in BMI (from 21.2 to 23 to 27.1 to 30 in men 20 to 44 years of age were associated with:

  1. a total cholesterol level 0.59 mmol/L (23 mg/dl) higher (P<0.01)
  2. A non-HDL cholesterol level 0.70 mmol/L (27 mg/dl) higher (P<0.01) and
  3. LDL cholesterol level 0.59 mmol/L (23 mg/dl) higher (P=0.03)

In middle-aged men (45-59 years) and older men (60-74 years) changes in BMI (from 21.2 to 23 to 23 to 27.1) were associated with smaller but still significant differences in

  1. total cholesterol levels (higher by 0.31 mmol/L (12 mg/dl (P<0.01) and 0.28 mmol/L (11 mg/dl (P<0.01, respectively
  2. non HDL cholesterol levels higher by 0.37 mmol/L (14 mg/l) P<0.01) and 0.25 mmol/L (10 mg/dl), P<0.01, respectively.
  3. LDL cholesterol unchanged

The BMI associated differences in TG (higher by 0.70 to 1.33 mmol/L (62 to 118 mg/dl P<0.001) and HDL cholesterol levels (lower by 0.18 to 0.39 mmol/L (7 to 15 mg/dl, P<0.001) were of similar magnitude in all age groups.

Author Conclusion:

Excess body weight is associated with deleterious changes in the lipoprotein profile. Higher BMI was associated at all ages with ­ TG, ¯ HDL cholesterol and ­ total and LDL cholesterol.

In young men, the higher total cholesterol was reflected mainly in the LDL cholesterol level; in middle-aged and older men, in the non-HDL fraction.

Programs to reduce CHD by improving lipid levels should include more emphasis on achieving and maintaining ideal body weight.

Since HDL cholesterol is inversely related to CHD, the fall in HDL cholesterol with ­ BMI should impart additional risk for CHD. Thus obesity may ­ risk for CHD in 2 ways—by ­ the concentration of atherogenic, apolipoprotein B-containing lipoproteins and by decreasing HDL cholesterol.

Funding Source:
Government: USDA-Agricultural Experiment Station
Industry:
American Egg Board
Commodity Group:
University/Hospital: University of Arizona, University of Oregon
Reviewer Comments:

Non-HDL cholesterol defined in this study as:

Difference between the total and HDL cholesterol levels and represents cholesterol in all lipoproteins that contain apolipoprotein B (VLDL cholesterol)

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? Yes
  3. Were explicit methods used to select studies to include in the review? Were inclusion/exclusion criteria specified andappropriate? Wereselectionmethods unbiased? Yes
  4. Was there an appraisal of the quality and validity of studies included in the review? Were appraisal methodsspecified,appropriate, andreproducible? Yes
  5. Were specific treatments/interventions/exposures described? Were treatments similar enough to be combined? Yes
  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? Yes
  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? Yes
  10. Was bias due to the review's funding or sponsorship unlikely? No