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UM: Role of Umami in the Regulation of Energy Intake (2014)

Citation:
 
Study Design:
Class:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:
  • To determine if individuals who were in a fed and orally stimulated state would experience early satiety
  • To observe differences in energy and macronutrient compositions eaten at a subsequent buffet meal after consuming a high-protein meal containing MSG.
Inclusion Criteria:
  • Healthy men and women
  • Between the ages of 18 and 65 years of age
  • Non-smokers
  • No medication except contraceptives
  • Not known to be allergic to MSG or other foods
  • No dietary restrictions
  • Low to moderate alcohol use
  • BMI between 20kg/m2 and 30kg/m2 
  • Weight stable.
Exclusion Criteria:
Not meeting the inclusion criteria.
Description of Study Protocol:

Recruitment

Subjects were recruited from advertisements in a local newspaper and around the Maastricht University, Netherlands.

Design

Randomized crossover trial.

Blinding Used

Single blind.

Intervention

  • HP meal with MSG + (inosine monophosphate-5) IMP
  • HP meal with no additives
  • HP meal with MSG only
  • Sham-fed meal of the first intervention (HP+MSG+IMP).

Statistical Analysis

  • Repeated measures ANOVA 
  • If an overall effect of condition was found, post-hoc analyses were done 
  • Pearson correlation analysis.
Data Collection Summary:

Timing of Measurements

Every week for five total trials:

  • Blood samples: T(min) = 0, 20, 50
  • 100mm visual analog scales: T = 0, 20, 30, 40, 50, 65
  • Energy and macronutrient intake analysis: T = 65.

Dependent Variables

  • Biomarkers: Glucose, insulin, glucagon-like peptide 1
  • Visual analog scales
  • Energy and macronutrient intake.

Independent Variables

  • HP+MSG+IMP
  • HP+MSG
  • HP alone
  • Sham-fed HP+MSG+IMP.

Control Variables

Water.
Description of Actual Data Sample:
  • Initial N: 22
  • Attrition (final N): 22, 100%
  • Mean age: Men, 44±19 years; women, 32±19 years; P=0.06
Other Relevant Demographics
Characteristics of men and women who completed the study
 
  Men Women P-Value
BMI (kg/m2) 26.5±3.8 23.7±4.5 0.05
Total body water (kg) 46.1±7.5 33.8±6.6 <0.001
Body fat mass (kg) 21.4±8.9 21.0±12.7 0.90
Body fat-free mass (kg) 63.2±10.8 46.3±8.9 <0.001
Dietary restraint 6.7±4.2 8.0±5.2 0.40
Lowest concentration of MSG+IMP tasted 0.34±0.22 0.29±0.24 0.64

Location

Netherlands.

Summary of Results:

Key Findings

  • Appetite ratings:
    • Compared to control, HP+MSG+IMP, HP only and HP+MSG all increased satiety and fullness, and decreased hunger, desire to eat and prospective consumption (P<0.05)
    • Sham feeding increased satiety and fullness and reduced hunger, desire to eat and prospective consumption, but the changes were less than observed in each of the three HP-fed conditions (P<0.01)
    • Fullness and satiety had a significant time interaction condition at T = 20 minutes (P<0.01).
  • Changes in glucose, insulin and glucagon-like peptide 1 (GLP-1):
    • Glucose and insulin concentrations were raised more following the three HP-fed conditions than either the sham or the control conditions (P<0.05)
    • GLP-1 concentrations were raised more greatly after the HP+MSG+IMP than the control (P=0.013), and all three HP-fed conditions raised the concentrations more than the sham-fed condition (P<0.05).
  • Energy and macronutrient intakes at the buffet:
    • An overall effect of condition was observed on absolute energy, protein, carbohydrate and fat intake compared to the control (P<0.001)
    • More energy was consumed following the HP+MSG compared with the HP-only condition (P=0.005)
    • Energy intake after each of the three HP-fed conditions when compared with both the control and sham-fed conditions were lower (P<0.001); however, the percent energy consumed at the second course was greatest for the HP+MSG condition, followed by HP+MSG+IMP and then the HP-only condition (P<0.01)
    • When macronutrient consumption is expressed as a percentage of total energy consumed only fat intake was significantly affected by meal condition, it was less following the conditions of HP+MSG+IMP and HP only compared with both the control and sham-fed conditions respectively (P<0.001).
  • Relationship between taste detection threshold for MSG+IMP and energy intake: A significant relationship between the lowest concentration of MSG+IMP tasted by subjects and energy intake at the second course was found (P=0.013).

Overall Findings

  • The addition of MSG (alone or in combination with IMP) to a HP meal did not influence the perceptions of appetite or satiety, or accelerate changes in the release of GLP-1, glucose or insulin, any more than a HP meal without MSG
  • The data suggests that the addition of MSG may increase energy intake at a second course
  • Sham feeding an HP meal with added MSG does not elicit cephalic responses that affect post-prandial satiety and subsequent food intake any more greatly than drinking an equal volume of water
  • The addition of MSG+IMP to a HP meal appears to only subtly increase its pleasantness; this effect is very subjective.
  • The taste detection threshold of individuals for the taste of MSG+IMP is negatively associated with energy intake at a subsequent ad libitum meal. 
Author Conclusion:
The addition of MSG to a HP meal does not influence perceptions of satiety but it may increase energy intake at a second course. Cephalic responses observed after the sham-fed condition were of similar magnitude as the control; thus, demonstrating that just tasting food is not enough to influence satiety and energy intake. 
Funding Source:
University/Hospital: Top Institute Food & Nutrition, Netherlands
Other: European DiOGenes program 2002-2006
Reviewer Comments:
  • The conditions and environment of the buffet provided to subjects are not clear and the author does not address the potential impact of subjects' increased level of comfort and ease to increase their intake both over time and by the second meal. This could have resulted in a false negative.
  • There are many potential confounding factors that seem to be missing or not being taken into account, such as:
    • Personal food preferences
    • Any supplements or bioactive substance intake
    • Physical activity
    • Dietary restraint
    • Other factors.
Quality Criteria Checklist: Primary Research
Relevance Questions
  1. Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies) Yes
  2. Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about? Yes
  3. Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice? Yes
  4. Is the intervention or procedure feasible? (NA for some epidemiological studies) Yes
 
Validity Questions
1. Was the research question clearly stated? Yes
  1.1. Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified? Yes
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated? Yes
  1.3. Were the target population and setting specified? Yes
2. Was the selection of study subjects/patients free from bias? Yes
  2.1. Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study? Yes
  2.2. Were criteria applied equally to all study groups? Yes
  2.3. Were health, demographics, and other characteristics of subjects described? Yes
  2.4. Were the subjects/patients a representative sample of the relevant population? Yes
3. Were study groups comparable? Yes
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) Yes
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? Yes
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) Yes
  3.4. If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis? No
  3.5. If case control study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable.) N/A
  3.6. If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")? N/A
4. Was method of handling withdrawals described? N/A
  4.1. Were follow-up methods described and the same for all groups? N/A
  4.2. Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.) N/A
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? N/A
  4.4. Were reasons for withdrawals similar across groups? N/A
  4.5. If diagnostic test, was decision to perform reference test not dependent on results of test under study? N/A
5. Was blinding used to prevent introduction of bias? Yes
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? Yes
  5.2. Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.) No
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? N/A
  5.4. In case control study, was case definition explicit and case ascertainment not influenced by exposure status? N/A
  5.5. In diagnostic study, were test results blinded to patient history and other test results? N/A
6. Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described? Yes
  6.1. In RCT or other intervention trial, were protocols described for all regimens studied? Yes
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? Yes
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? Yes
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? Yes
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? No
  6.6. Were extra or unplanned treatments described? No
  6.7. Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups? Yes
  6.8. In diagnostic study, were details of test administration and replication sufficient? N/A
7. Were outcomes clearly defined and the measurements valid and reliable? Yes
  7.1. Were primary and secondary endpoints described and relevant to the question? Yes
  7.2. Were nutrition measures appropriate to question and outcomes of concern? Yes
  7.3. Was the period of follow-up long enough for important outcome(s) to occur? Yes
  7.4. Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures? N/A
  7.5. Was the measurement of effect at an appropriate level of precision? N/A
  7.6. Were other factors accounted for (measured) that could affect outcomes? N/A
  7.7. Were the measurements conducted consistently across groups? N/A
8. Was the statistical analysis appropriate for the study design and type of outcome indicators? Yes
  8.1. Were statistical analyses adequately described and the results reported appropriately? Yes
  8.2. Were correct statistical tests used and assumptions of test not violated? Yes
  8.3. Were statistics reported with levels of significance and/or confidence intervals? Yes
  8.4. Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)? N/A
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? No
  8.6. Was clinical significance as well as statistical significance reported? Yes
  8.7. If negative findings, was a power calculation reported to address type 2 error? N/A
9. Are conclusions supported by results with biases and limitations taken into consideration? Yes
  9.1. Is there a discussion of findings? Yes
  9.2. Are biases and study limitations identified and discussed? Yes
10. Is bias due to study's funding or sponsorship unlikely? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.2. Was the study free from apparent conflict of interest? Yes