EAL

UM: Umami Compounds and Sodium (2013)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To establish whether the taste characteristics of a conventionally salted soup could be reproduced in soups of substantially lower NaCl level with the help of added glutamate.
To establish whether calcium diglutamate (CDG) was equivalent to monosodium glutamate (MSG) in its effects on taste characteristics.

Inclusion Criteria:

Young adults or university students currently enrolled in a psychology course
Provided written informed consent.

Exclusion Criteria:

Heavy smokers
Persons who reported ever having suffered a reaction to MSG.

Description of Study Protocol:

Recruitment

Recruited from the University of Tasmania Australia
Students were primarily enrolled in psychology courses.

Design

Randomized crossover trial (authors noted that study design was cross-sectional with multiple measurements on each subject). Each person received one exposure to each of the soups in an individually generated random order.

Blinding Used

Sampling was carried out with salt and glutamate content withheld from subjects.

Intervention

Subjects tasted 32 soups, with all possible combinations of four NaCl concentrations (0-150mM), four glutamate levels (0-43 mM) and two glutamate types (MSG, CDG).

Statistical Analysis

Analyses used the Statistica for Windows Version 5 software package
Comparisons with P<0.01 were treated as significant
The data were subjected to three-way analysis of variance (ANOVA) with repeated measures on four factors: Salt level x glutamate level x cation
Further pairwise comparisons were made using the Tukey HSD procedure.

Data Collection Summary:

Timing of Measurements

Over two consecutive days, all subjects tasted 32 soups
On one day, the 16 soups of the CDG series were sampled and on the other day the MSG series was sampled with half of the subjects sampling the CDG series first, in random order.

Dependent Variables

Rating of each soup on six scales (liking, flavor-intensity, familiarity, naturalness of taste, richness of taste, saltiness)
Participants were also required to rate each soup for six taste characteristics.

Independent Variables

Subjects tasted 32 soups maintained at 85° to 90° Celsius, with all possible combinations of four NaCl concentrations (0-150mM), four glutamate levels (0-43mM) and two glutamate types (MSG, CDG)
- Soups were tested based on a simple pumpkin soup with no added salt or glutamates. This was produced by the Australian Defense Nutrition Research Center at Scottsdale, Tasmania.
- It contained 160g pumpkin and 60g onion, cooked and blended up in 1L of water and then freeze dried
- The freeze-dried powder after addition of NaCl and glutamates as was re-constituted with water 1,000ml per 60g powder
- Two different aliquots of this common freeze-dried starting material NaCl and MSG were added to produce a series of 16 soups that included all possible combinations of four concentrations of added NaCl and four concentrations of added MSG
- A further 16 soup series was produced using all possible combinations of the same four concentrations of added CDG
- A 30ml aliquot of each soup was tasted and swallowed after tasting.

Description of Actual Data Sample:

Initial N: 120 participants
Attrition (final N): 120 participants (67% female)
Age: Average age was 22 years
Ethnicity: Caucasian
Location: Tasmania, Australia.

Summary of Results:

Key Findings

For all six rating scales, ANOVA indicated very strong main effects for NaCl concentration (P<0.0001)
Glutamate also showed a very strong (P<0.0001) main effect for five of the scales, its effect on naturalness of taste being marginally less so (P=0.0003)
A 50 or 85mM NaCl soup with added CDG or MSG is rated as high as or higher than a 150mM NaCl soup free of added glutamate on five of the six scales (the exception being saltiness)
CDG and MSG have equivalent effects.

Author Conclusion:

Addition of glutamate allows substantial reductions in sodium content of soup without significant deterioration of taste. CDG and MSG have equivalent effects, but use of CDG permits a greater reduction in sodium intake.

Funding Source:

Other:

International Glutamate Technical Committee (IGTC)

Reviewer Comments:

Regarding study design, authors noted that study design was cross-sectional with multiple measurements on each subject, but each person received one exposure to each of the soups in an individually generated random order.

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)	No
	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?	N/A
	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?		Yes
	4.1.	Were follow-up methods described and the same for all groups?	Yes
	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%.)	Yes
	4.3.	Were all enrolled subjects/patients (in the original sample) accounted for?	Yes
	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?	N/A
	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?	Yes
	6.6.	Were extra or unplanned treatments described?	Yes
	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?	Yes
	7.5.	Was the measurement of effect at an appropriate level of precision?	Yes
	7.6.	Were other factors accounted for (measured) that could affect outcomes?	Yes
	7.7.	Were the measurements conducted consistently across groups?	Yes
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)?	N/A
	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