EAL

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 examine the association between MSG intake and body mass index (BMI) in apparently healthy middle-aged Chinese adults.

Inclusion Criteria:

Participant in the INTERMAP study
Men and women of ages 40 to 59 years of age.

Exclusion Criteria:

Individuals on a special diet
Have diabetes or cardiovascular disease.

Description of Study Protocol:

Recruitment

Individuals were recruited from rural sample areas in China (two in the north and one in the south); a subset of the INTERMAP study.

Design

Retrospective cohort study.

Statistical Analysis

Logistic regression to estimate odds ratios for overweight
MSG users divided into tertiles according to MSG intake
Multiple linear regression analysis was used to assess dose-response relation between MSG intake and BMI
Gender specific analyses were also done
Dietary and non-dietary potential confounders were identified based mainly on statistical tests and included:
- Age
- Gender
- Sample
- Smoking status
- Physical activity
- A 24-hour sodium excretion
- Total energy intake
- Animal protein
- Saturated fat
- Monounsaturated fat
- Total available carbohydrate
- Fiber.
P-values were two-sided with P.

Data Collection Summary:

Timing of Measurements

Each participant visited the research centers four times (two visits on consecutive days, then two visits on average three weeks later)
Dietary data was collected at each visit
Two 24-hour urine specimens were collected an average three weeks apart.

Dependent Variables

Weight status: In accordance with recommendations of the World Health Organization (WHO) and the
International Association for the Study of Obesity for Asian populations, overweight was defined as between BMI 23.0kg/m² or more and BMI 25.0kg/m² or more.

Independent Variables

MSG use or consumption: Participants were asked whether they used MSG in food preparation, then asked to demonstrate the amount added during food preparation, using actual MSG. The amounts shaken out were weighed. For soy sauce, the amount of MSG was derived from the labeling or recipes provided by the manufacturers. Recipes were obtained for commercially processed foods. An average MSG intake from four 24-hour multi-pass recalls per person was used in the analyses.
The control group was a group of non-MSG.

Control Variables

Age
Gender
Sample
Smoking status
Physical activity
Total energy intake
Five nutrients.

Description of Actual Data Sample:

Initial N: 839
Attrition (final N): 752 (84.2% men, 80.6% women; including 132 non-users of MSG)
Age: 40 to 59 years
Ethnicity: Chinese (assumed)
Anthropometrics: Average BMI was 22.3 (SD 2.7) for men and 23.6 (SD 3.6) for women.

Location

Beijing
Shanxi Province
Guangxi Zhuang Autonomous Region.

Summary of Results:

Key Findings

**Odds Ratio and 95% Confidence Interval for Overweight by MSG Intake**
	Non-users of MSG a: N=56 b: N=25	Tertile 1 a: N=98 b: N=55	Tertile 2 a: N=97 b: N=52	Tertile 3 a: N=85 b: N=42	P-value
Model 1a	1.0	1.27 (0.80 to 2.0)	1.67 (1.03 to 2.72)	2.50 (1.43 to 4.38)	<0.01
Model 2a	1.0	1.42 (0.88 to 2.30)	1.84 (1.10 to 3.06)	2.51 (1.40 to 4.52)	<0.01
Model 3a	1.0	1.30 (0.80 to 2.12)	1.59 (0.94 to 2.72)	2.10 (1.13 to 3.90)	0.03
Model 1b	1.0	1.61 (0.92 to 2.82)	2.33 (1.28 to 4.25)	3.37 (1.68 to 6.75)	<0.01
Model 2b	1.0	1.83 (1.03 to 3.25)	2.59 (1.39 to 4.83)	3.21 (1.55 to 6.65)	<0.01
Model 3b	1.0	1.77 (0.98 to 3.20)	2.36 (1.23 to 4.52)	2.75 (1.28 to 5.95)	0.04

a: BMI 23.0 or more; b: BMI 25.0 or more.

Model 1: Adjustment for age, gender and sample; Model 2: Model 1 with additional adjustment for smoking status, heavy activity, total energy intake and 24-hour excretion of sodium; Model 3: Model 2 with additional adjustment for intakes (expressed as caloric density) of animal protein, saturated fat, monounsaturated fat, total carbohydrate and fiber.

Other Findings

Median MSG intake (range in g per day):
- Non-MSG users (N=132) 0.00 (0.00 to 0.00)
- Tertile 1 (N=201) 0.08 (0.01 to 0.15)
- Tertile 2 (N=215) 0.28 (0.15 to 0.45)
- Tertile 3 (N=204) 0.70 (0.45 to 3.23).
With 1g higher MSG intake, the estimate was BMI higher by 0.61kg/m²
Prevalence of overweight was significantly higher for MSG users than non-users: With BMI 23.0 or higher as the criterion for overweight, the multi-variable odds ratio (model 3) for MSG users in the highest tertile of MSG intake compared to non-users was 2.10 (P=0.03); with BMI 25.0 or higher, it was 2.75 (P=0.04)
Interactions between MSG intake and gender were non-significant.

Author Conclusion:

A positive relationship of MSG intake to BMI that persisted with controlling for physical activity and total energy intake among apparently healthy Chinese adults. MSG intake was significantly related to prevalence of overweight.

Funding Source:

Government:

NIH Grants; national and local agencies in China, Japan and UK

Not-for-profit

Chicago Health Research Foundation

Other non-profit:

Reviewer Comments:

Sample sizes across groups were not comparable; gender differences across samples sizes are unknown
Data is all based on 24-hour recalls and only over a short period of time; does not give accurate longitudinal data on MSG and weight relationship
Dose response validation technique is not an accurate methodology when utilizing short-term data when addressing lifestyle-related issues
Adjustments made for intake and physical activity were appropriate but limited, understanding how correlation impacts actual biochemical response mechanisms of appetite and satiety. May have benefited from collection of additional measures.
Blinding and potential testing bias were not accounted for
Socio-economic differences were also not taken into consideration, all were from rural regions but each region has significant socio-economic differences that could account for food and MSG use differences and perceptions
Brief details on design, data collection, measurement procedures and participant characteristics because these were previously published.

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?	N/A
	3.3.	Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.)	N/A
	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?	Yes
	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?	Yes
	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?		???
	5.1.	In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate?	???
	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.)	???
	5.3.	In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded?	???
	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?		No
	6.1.	In RCT or other intervention trial, were protocols described for all regimens studied?	N/A
	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?	No
	6.4.	Was the amount of exposure and, if relevant, subject/patient compliance measured?	No
	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?	N/A
	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?	No
	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?	No
	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)?	Yes
	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