Disorders of Lipid Metabolism and Nuts

Citation:

Kris-Etherton PM, Zhao G, Binkoski AE, Coval SM, Etherton TD. The effects of nuts on coronary heart disease risk. Nutr Rev. 2001;59:103-111.

Worksheet created prior to Spring 2004 using earlier ADA research analysis template.
PubMed ID: 11368503
 
Study Design:
Narrative Review
Class:
M - Click here for explanation of classification scheme.
Quality Rating:
Neutral NEUTRAL: See Quality Criteria Checklist below.
Research Purpose:

1.  To review the epidemiologic and clinical studies that have demonstrated the effects of nuts on cardiovascular health

2.  To address the question of whether the reduction in CHD risk can be explained solely by the fatty acid profile of nuts or if other compounds in nuts contribute to risk reduction. 

Inclusion Criteria:

Must be:

  1. a large epidemiological study showing a decreased risk in CHD due to nut consumption or
  2. a clinical study evaluating the effects of diets containing nuts on lipid and lipoprotein endpoints.

Criteria for inclusion of articles:  "studies to date"; no other specific criteria given

Exclusion Criteria:

  1. studies not epidemiologically or clinically designed.
  2. study conducted before 1991.

Description of Study Protocol:

Narrative Review: Protocol for review not described.  Reports of epidemilogic and clinical studies summarized and synthesized in tables and narrative.

Epidemiologic studies:

  • Large cohort studies examined the association of nut consumption with CHD.
  • Nut consumption assessed using FFQ

 Clinical Studies:

Test blood lowering effect of average American diet or low fat diet compared to same diet with nuts.  Many examined the effect of nuts on fatty acid profile of the diet. 

Meta-analysis:

Diet composition data from 8 clinical studies were used in the cholesterol predictive equations from Mensink and Katan, and Hegsted to predict changes in total and LDL cholesterol. These values were then compared with the observed changes from the clinical studies.

 

Data Collection Summary:

Epidemiologic studies:

Frequency of nut consumption (1 ounce serving per week), endpoints:

  • total CHD mortality
  • definite fatal CHD
  • nonfatal MI
  • total cardiac death or sudden death.

Clinical studies:

Diet compositin, baseline and endpoints lipids/lipoproteins

Meta-analysis:

Predicted change in total and LDL cholesterol.

Estimated percent changes in CHD risk with isocaloric substitution of fat from nuts for carbohydrate in the diet

Description of Actual Data Sample:

Actual Sample:

Reports from:

  • 5 large epidemiologic studies involving over 200,000 men and women
  • 3 controlled feeding trials with total of 42 male and 28 female subjects
  • 8 free-living subject studies with total of 90 male and 109 female subjects

Summary of Results:

Epidemiological Studies and Results:

  • California Seventh-Day Adventist Health Study (Fraser, 1995)
  • Adventist Health Study (Fraser, 1992; Fraser, 1997a; Fraser, 1997b)
  • Iowa Women's Health Study (Prineas, 1993; Kushi, 1996)
  • Nurses' Health Study (Hu, 1998)
  • Cholesterol and Recurrent Events (CARE) Study (Brown, 1999)
  • Physicians Health Study (Albert, 1999) 11 clinical studies

Results from Epidemiological Studies:

An inverse dose-response existed between frequency of consumption of nuts and RR of CHD in men and women.

Consuming nuts (1 oz. serving) more than 1 time/wk significantly decreased the relative risk of CHD.

RR for nut consumption >4 or 5 time/wk compared to <1 time/wk
Total CHD           .45 to .65
Fatal CHD           .52 to .61
Nonfatal CHD      .49 to .68

Clinical Studies and Lipid Change Results:

Controlled Feeding Studies

Curb, 2000--RCT (crossover)
Macademia nuts fed for 30 d 15 M, 15 F
•  Baseline LDL-Chol 3.47 mmol/L vs. 30 days on nuts: 3.22 mmol/L (P<0.01)

Kris-Etherton, 1999 RCT (double-blind crossover) 
Peanuts/peanut butter fed for 5 wk 9 M, 13 F w hypercholesterolemia
• Baseline LDL-chol: 3.05 mmol/L vs. 3.03 mmol/L after 5 weeks (P<0.05).

Sabate, 1993 RCT (crossover)
84 g/d of walnuts for 4 wk 18M
•  LDL-chol 2.43 mmol/L compared to 2.90 mmol/L for those on diet without walnuts (P<0.001)

Free-Living Subjects Studies

Abbey, 1994 Consecutive supplemental trial for 3 wk
84 g almonds/d or 68 g walnuts/d 16 M
•  LDL-chol 3.21 mmol/L on almonds, 3.26 mmol/L on walnuts and 3.58 mmol/L for control dieet (P<0.001)

Chisholm, 1998 RCT (crossover)
78 g/d of walnuts for 4 wk 21M w hypercholesterolemia
•  LDL-chol 3.94 mmol/L vs 4.10 mmol/L low fat diet (P<0.001)

Colquhoun, 1996 RCT (crossover)
50 to 100 g macademia nuts/d for 4 wk 7 M, 7 F w hypercholesterolemia
•  Baseline LDL-chol: 4.13 mmol/L compared with 4 wk: 3.68 mmol/L (P<0.01)

Edwards, 1999 RCT (crossover)
Pistachio uts for 3 wk 4 M, 6 F w hypercholesterolemia
•  No significant effect on LDL-chol (baseline: 4.65 mmol/L vs. 3 wk: 4.08 mmol/L

Morgan et al. RCT (parallel artm)
68 g pecans/d for 8 wk 4 M, 15 F
•  LDL-chol at baseline: 2.61 mmol/L vs 2.46 mmol/L at 8wk (P<0.005)

O'Bryne, 1997 Parallel arm
35-68 g peanuts/d for 6 mo 25 F w hypercholesterolemia
•  LDL-chol at baseline: 4.71 mmol/L vs. 4.16 mmol/L (P<0.01).

Spiller, 1998 RCT (parallel arm)
Almonds 100g/d for 4 wk
•  LDL-chol: baseline 4.29 mmol/L compared to 4.16 mmol/L after 4 wk (P<0.01)

Zambon, 2000 RCT (crossover)
Walnuts 41-56 g/d for 6 wk 26 M, 23F w hypercholesterolemia
•  LDL-chol at baseline: 5.50 mmol/L vs 4.48 mmol/L after 6 wk (P<0.001).

Collectively, the clinical studies indicate that inclusion of nuts in a blood cholesterol-lowering diet has favorable effects on lipid and lipoprotein profiles (as would be expected based on the fatty acid and cholesterol profile of the diet).

Six of 7 studies with a hyperlipidemic subjects found significant cholesterol lowering.

Meta-analysis:

4 of 8 studies had greater cholesterol-lowering than predicted from change in fatty acid composition of diet.

Using data from the Hu study, the predicted percent change in CHD risk attributable to the changes in the fatty acid profile after consuming nuts was compared to that reported.  CHD risk was lower in most instances when nuts were consumed.

 

Author Conclusion:

Author's Conclusions:

There is consistent evidence, especially from epidemiologic studies, that nuts have a strong protective effect against CHD morbidity, and mortality in different population groups.

Clinical studies have reported total and low-density lipoprotein cholesterol-lowering effects of health-healthy diets that contain various nuts or legume peanuts.

Evidence from a growing database of clinical studies with nuts indicates that part of the cardioprotective effect is due to their favorable effects on plasma lipids and lipoproteins due to the fatty acid composition of the diet when nuts replace dietary SFA and/or carbohydrate.

It is appropriate to recommend inclusion of nuts in a healthy diet that meets energy needs to reduce CHD and there s a need to provide dietary guidance necessary for the public to understand how to plan heart healthy diets that include nuts.

Funding Source:
Not-for-profit
0
Foundation associated with industry:
Reviewer Comments:

The authors did what they set out to do, and provide an excellent summary of studies that show the benefits of nuts on serum lipids and the prevention of CHD. The information is organized in table format for easy review. A limitation is the authors' failure to describe how articles were selected.  Thus the reader is unable to determine if other studies have been done with negative findings.

Quality Criteria Checklist: Review Articles
Relevance Questions
  1. Will the answer if true, have a direct bearing on the health of patients? Yes
  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
  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
  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
  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
  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
  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
  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
  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? 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
  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
  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
  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
  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
  10. Was bias due to the review's funding or sponsorship unlikely? Yes