EAL

Dried Beans and Peas - CNPP (DGAC)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To identify and evaluate evidence for or against four propositions related to soy foods and weight loss:

Certain soy foods will improve weight and fat loss when fed at isocaloric levels
Certain soy foods will improve weight and fat loss when included as part of a diet by affecting caloric intake
Certain soy foods will prevent or improve risk factors related to glucoregulatory function and cardiovascular health during weight loss
Certain soy foods will minimize the loss of bone mass during weight loss.

Inclusion Criteria:

Literature that provided scientific evidence, including in vitro, animal, epidemiologic and clinical studies, either supporting or refuting four propositions about soy and weight loss and the related health benefits.

Exclusion Criteria:

None specified.

Description of Study Protocol:

Literature Search

Search engines used: PubMed; ISI Web of Science
Keywords (combinations): Soy, weight loss, fat loss, cholesterol, cardiovascular, glucose, LDL, HDL, bone, osteoporosis, isoflavone.

Design

Systematic, evidence-based review.

Statistical Analysis

Not completed.

Data Collection Summary:

Dependent Variables

Weight loss
Fat loss
Risk factors related to glucoregulatory function and cardiovascular health during weight loss:
- Indices of glucose metabolism
- LDL-Cholesterol (LDL-C)
- HDL-Cholesterol (HDL-C)
- Triglycerides (TG)
Bone loss.

Independent Variables

Soy intake.

Control Variables

Proposition one related to studies where certain soy foods were fed at prescribed isocaloric levels.

Description of Actual Data Sample:

Initial N:
- PubMed: 211
- ISI Web of Science: 12 that were different from the 211 identified by PubMed
Attrition (final N): As above
Location: International studies.

Summary of Results:

Key Findings

Certain soy foods will improve weight and fat loss when fed at isocaloric levels; generally supportive evidence in animal studies, but there is no compelling support in human studies
Certain soy foods will improve weight and fat loss when included as a part of a diet by affecting caloric intake; limited supportive evidence in animal and human studies
Certain soy foods will prevent or improve risk factors related to glucoregulatory function and cardiovascular health during weight loss; some evidence supporting this, but additional evidence is needed before conclusions can be made
Certain soy foods will minimize the loss of bone mass during weight loss; no data available pertinent to this proposition
Proposition 1: Certain soy foods will improve weight and fat loss when fed at prescribed isocaloric levels (i.e., the two diets contain the same total energy):
- In vitro studies provide limited support
- Animal studies are generally supportive compared with casein; the magnitude of effect varied among studies
- Epidemiologic studies provide limited data: Several studies with inverse associations (i.e., higher soy consumption associated with lower weight); self-reporting identified as a limitation of these observational studies
- Clinical studies provide no compelling support; soy was equivalent to other protein sources during low calorie intake
Proposition 2: Certain soy foods will improve weight and fat loss when included as part of a diet by affecting caloric intake:
- In vitro studies: Not applicable
- Animal studies provide limited support; only one study was identified that suggested that soy protein, along with other protein sources, may reduce short-term caloric intake in animals
- Epidemiologic studies provide no compelling support; one report showed equivalent caloric intake among people consuming higher and lower amounts of soy
- Clinical studies provide limited support for short-term effects; there is no data for long-term effects
Proposition 3: Soy will prevent or improve risk factors related to glucoregulatory function and cardiovascular health during weight loss:
- Soy will improve indices of glucose metabolism
  - In vitro studies provide limited support; genistein may improve glucose metabolism
  - Animal studies provide limited support; two studies identified soy to be more beneficial than casein
  - Epidemiologic studies provide no compelling support
  - Clinical studies provide no compelling support when controlling for weight loss
- Soy will decrease LDL-C levels:
  - In vitro studies: Not applicable
  - Animal studies provide some support
  - Epidemiologic studies provide limited support
  - Clinical studies provide some support; two studies indicated that soy increased HDL-C levels in post-menopausal women
- Soy will increase HDL-C levels:
  - In vitro studies: Not applicable
  - Animal studies: Limited data
  - Epidemiologic studies provide limited support; one report indicated that genistein consumption was positively associated with increased HDL
  - Clinical studies provide some support; two studies indicated that soy increased HDL levels in post-menopausal women
- Soy will decrease triglycerides:
  - In vitro studies: Not applicable
  - Animal studies: Generally supportive
  - Epidemiologic studies: Limited data
  - Clinical studies: Generally supportive
Proposition 4: Soy will minimize the loss of bone mass during weight loss
- In vitro studies: Not applicable
- Animal studies: Limited support
- Epidemiologic studies: No available data during weight loss
- Clinical studies: No available data during weight loss.

Author Conclusion:

Current data suggest that soy foods are as good as other protein sources for promoting weight loss and there is a suggestive body of evidence that soy foods may confer additional benefits, but results must be carefully interpreted and additional evidence is needed before making firm conclusions concerning soy foods and weight loss.

Funding Source:

University/Hospital:

University of Alabama at Birmingham

Reviewer Comments:

It is unclear if the studies that are summarized are the only ones used to draw conclusions or how many studies were included in the final review
Authors note that soy food nomenclature is not standardized, which makes it challenging to compare soy components across studies, and most of the animal and clinical studies use different formulations of soy products and compare soy protein with milk protein sources.

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?	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
	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?	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?	N/A
	5.	Were specific treatments/interventions/exposures described? Were treatments similar enough to be combined?	N/A
	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?	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?	Yes
	10.	Was bias due to the review's funding or sponsorship unlikely?	Yes