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Disorders of Lipid Metabolism and Nuts


Fraser GE. Nut consumption, lipids, and risk of coronary event. Clin Cardiol. 1999; 22 (Suppl III), 11-15. Review.

PubMed ID: 10410300
Study Design:
Meta-analysis or Systematic Review
M - Click here for explanation of classification scheme.
Quality Rating:
Neutral NEUTRAL: See Quality Criteria Checklist below.
Research Purpose:

To examine the possibility that nuts may provide anti-atherogenic effects by lowering blood low-density lipoprotein (LDL) cholesterol levels. 

Inclusion Criteria:

Not provided.

Exclusion Criteria:

Not provided.

Description of Study Protocol:

Not discussed.

Data Collection Summary:
  • Berry, et al in a randomized crossover study with 17 or 18 young men over two, 12-week feeding periods. Total fat was 33% to 34% of calories:
    • MUFA: almonds, olive oil, or avocados as a source of fat in diet
    • PUFA: walnuts, safflower, or soy
    • High carbohydrate diet
  • Spiller, et al in nonrandomized three studies with concurrent controls:
    • Study I in a parallel study design for four weeks: total of 30 hypercholesterolemic subjects:
      • One group consuming a low-fat diet plus 100g per day of almonds
      • One group consuming a low-fat diet plus 48g fat from butter
    • Study II 26 men and women from cardiac rehabilitation unit consumed usual diet containing grains, beans, vegetables, fruit and low fat dairy or usual diet plus 100g almonds and almond oil for nine weeks; consuming 37% of calories as fat
    • Study III 48 hypercholesterolemic subjects with mean serum cholesterol of 251mg per dL, four-week parallel study, baseline diet supplemented with one of these three:
      • 100g almonds
      • 48g olive oil and 113g cottage cheese
      • 85g cheddar cheese plus 28g butter
  • Sabate, et al in controlled cross-over study with 18 young men two, four weeks for each study diet; 30 % fat calories:
    • Basic diet plus 85g per day of walnuts (PUFA)
    • Basic diet plus other sources of fat (10% SFA, 10% MUFA, 10% PUFA)
  • Abbey, et al in Australia with16 men over consecutive three-week periods, supplemental diet:
    • Match the fatty acid profile of the usual diet
    • Usual diet plus 1.84g MUFA-rich almonds per day
    • Usual diet plus two 68g PUFA-rich walnuts per day
  • Cohort Studies
    • California Seventh-Day Adventists: 34,000 non-Hispanic, Caucasians; observed the number of times per week the subjects consumed nuts. The dose-response association with CHD risk was calculated.
    • Iowa Women’s Health Study: 34,000 women; observed consumption of nuts per week and reduction at risk of CHD
    • Nurses’ Health Study: 86,000 nurses; those consuming five ounces per week were compared with those who consumed less than one ounce of nuts per week
    • Physicians’ Health Study: 22,000 male physicians; observed nut consumption and risk of cardiac death and sudden death.


Description of Actual Data Sample:

See above for each study.

Summary of Results:
  • Berry, et al: Compared with the baseline diet, both the increased MUFA and PUFA diets decreased total and LDL cholesterol levels 10 to 20% without changing HDL lipoprotein cholesterol. Compared with the high carbohydrate diet, the high MUFA diet lowered total and LDL cholesterol.
  • Spiller, et al:
    • Study 1: The first group experienced a 15% drop in total cholesterol compared with the second group
    • Study 2: Compared with the "usual diet", total and LDL cholesterol declined 9% and 12%, respectively
    • Study 3: Total and LDL cholesterol levels were lowered on the baseline diet plus almonds and baseline diet plus olive oil and cottage cheese, but increased on baseline diet plus cheddar cheese (differences significant P<0.001). There was virtually no effect on HDL cholesterol.
  • Sabate, et al: Total cholesterol dropped 12.4%, LDL 16.3% and a small drop in HDL cholesterol
  • Abbey, et al: LDL cholesterol was decreased with almonds and walnuts added to usual diet, whereas HDL did not change
  • Cohort studies (California Seventh-Day Adventists Study, Iowa Women's Study, Nurses' Health Study, and Physicians' Health Study): All consuming large quantities of nuts had lower CHD risk than their counterparts eating lower quantities of nuts. Eating nuts frequently is associated with a risk of CHD 30% to 50%. Possible mechanisms include:
    • Decrease of LDL cholesterol
    • Antioxidant actions of vitamin E 
    • Effects of nitric acid on the endothelium and platelet function.
    • Nuts are a source of certain flavenoids, polyphenols and sterols. They are also a high source of MUFA, vitamin E, fiber, magnesium and arginine (a precursor of nitric acid).
Author Conclusion:
  • Data from several feeding trials in which quantities of various types of nuts were added to the diet consistently suggest that such supplements are at least as effective as or superior to fats in the recommended Step I American Heart Association Diet
  • Levels of LDL are equal to or better than those observed when subjects eat the recommended diet
  • Four of the largest cohort studies (California Seventh-Day Adventists (men and women separately); women in Iowa; male physicians; and female nurses) have reported that eating nuts frequently is associated with a decreased risk of coronary heart disease of the order of 30 to 50%.
Funding Source:
University/Hospital: Loma Linda Univeristy
Reviewer Comments:


  • Large sample sizes in cohort studies
  • Diverse populations.


  • Based on the various nut feeding studies, the small amount of nuts most people consume would be expected to result in a reduction of total cholesterol at most by 10%. This would be expected to result in a reduction in CHD events of approximately 25%, yet the cohort studies observe 35 to 50% reductions. This suggests that other confounding factors influence these findings.
  • The epidemiologic studies are observational. Potential confounders may not have been identified.
  • Were nut-consumers different in some way that accounts for decreased risk?
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? N/A
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? N/A
  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? 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? 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? Yes
  10. Was bias due to the review's funding or sponsorship unlikely? ???