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NNNS: Hyperlipidemias (2006)

Citation:
 
Study Design:
Class:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:
The study evaluated the effect of lower sweetener concentrations and the contribution of their sweetness level and palatability.
 
 
Inclusion Criteria:
  • Healthy adults, taking no medications and not adhering to any therapeutic diet
  • Customary fat intake, assessed by the Eating Pattern Assessment Tool (EPAT), was 23.7±1.2 units on a scale ranging from 12 (low) to 40.
Exclusion Criteria:
Description of Study Protocol:

Recruitment

  • Participants were recruited by public advertisement
  • The protocol was approved by the committee on the use of human research subjects at Purdue University
  • There were 22 participants: 12 male and 10 female.

Design

  • After a 10-hour overnight fast, a baseline blood sample (19ml) was drawn from a antecubital vein
  • Subjects consumed a milkshake within one minute, followed by ingestion of 25ml of water and the completion of chemosensory and health questionnaires
  • Subjects were allowed to leave the testing room between sessions, but returned to provide additional blood samples and health questionnaires at two, four, six and eight hours following ingestion of the lipid load
  • Each participant completed four sessions, during which milkshakes were administered.
  • Conditions were randomized and included:
    • 108 g dairy cream
    • 108g dairy cream plus 30g fructose
    • 108g dairy cream plus 17.5g glucose
    • 108g dairy cream plus one g aspartame.

Blinding Used 

  • Participants were informed that the purpose of the study was to evaluate how the digestion of fats is influenced by the level of its intake.

Statistical Analysis
  • Friedman Two-way ANOVA: Test the effects of sweetness and palatability on the primary dependent variable and plasma TG concentrations
  • Wilcoxon matched-pairs signed Rank tests: Used for paired comparisons
  • Area under the curve (AUC) for TG from stimulus ingestion to return to baseline were computed by the trapezoidal method
  • Repeated-measures ANOVAS: Total HDL, LDL, cholesterol, insulin and glucose changes
  • Baseline measures of BMI, TG and insulin concentrations, as well as EPAT results, were correlated with peak and AUC TG values by Spearman’s correlations.
  • Statistical significance: P≤0.05.
Data Collection Summary:

Timing of Measurements

  • At the end of the second session, participants were asked to complete the EPAT
  • Following the third and fourth sessions, participants completed sensory tests in order to determine whether the milkshakes were distinguishable from one another.

Sensory Testing

  • A triangle test was administered with the milkshake containing fructose and the milkshake containing aspartame following completion of the third treatment session. Ten sets of three stimuli (five ml each) were presented, two alike and one different.
  • Participants were required to sip and identify the odd sample. After the fourth treatment session, a modified Harris-Kalmus procedure was conducted: 14 samples (five ml each), seven containing fructose and seven containing aspartame, were presented in random order a single time and participants were asked to assign like samples to unique groups.
  • Participants were asked to rinse with water between samples. Immediately following ingestion of each milkshake, participants rated them for sweetness, bitterness, saltiness, sourness, oiliness, creaminess, fat level and pleasantness on 15-point category scale with end points of "not at all" and "extremely" for intensity and "very unpleasant" and "very pleasant" for palatability.

Hematology

  • Plasma insulin and glucose concentrations were determined at baseline and two, four, six and eight hours after milkshake ingestion, using a Linco-specific Human Insulin RIA Kit and glucose analyzer. SerumTG, cholesterol and high-density lipoprotein cholesterol concentrations were determined at the same time by an enzymatic procedure. Low-density lipoprotein cholesterol concentration at each time point was calculated using the equation LDL=(cholesterol-HDL)-(TG/5).
Description of Actual Data Sample:
  • Initial N: 22 (12 male, 10 female)
  • Attrition: N/A
  • Age: Mean age 27.3±6.3 years
  • Anthropometrics: Body mass index was 25.3±4.5 kg/m2.
Summary of Results:
  • The fructose-supplemented milkshake resulted in a significantly higher value (38%) than the plain milkshake (Z-score=2.1, P=0.03)
  • The fructose (Z-score=2.0, P=0.05) and glucose-supplemented milk shakes (Z-score=2.2, P=0.03) led to significantly higher AUC values, compared to the aspartame treatment: 30% and 51%, respectively
  • There were no significant differences between responses to aspartame and plain (Z-score=0.26, P=0.79) or between fructose and glucose- sweetened shakes (Z-score=0.63, P=0.53).
Mean (SE) Triacylglycerol Concentration Prior to Milkshake Ingestion and Peak and AUC Values after Consumption of an Unsweetened Shake and Ones Sweetened with Aspartame, Glucose or Fructose

  Plain Aspartame Glucose Fructose
TG baseline (mmol/dL) 1.02±0.13 1.02±0.15 1.11±0.18 0.92±0.14
TG peak (mmol/dL) 1.64±0.18 1.71±0.28 1.91±0.30 1.72±0.25
TG AUC (mmol/dL x 8 hours)
 17.05±2.94a,b 18.06±4.75a 27.32±7.23b,c 23.48±4.97c

  • AUC values, followed by dissimilar letters differ significantly (all P<0.05)
  • All milkshakes led to significant elevations of TG at the two- and four-hour time points (all P<0.05).
  • At six hours, only the glucose and fructose values remained significantly higher than baseline (both P<0.05).
  • There was an overall treatment effect seen at both the four-hour and six-hour time points:
    • At four hours, TG concentrations were higher after the fructose treatment, relative to plain milkshake ingestion (Z-score=2.0, P=0.04)
    • At six hours, TG concentrations were higher with the fructose treatment, when compared to aspartame treatment (Z-score=3.0, P=0.0030) and plain milkshake ingestion (Z-score=2.6, P=0.01). Ingestion of the glucose milkshake led to higher values than ingestion of aspartame milkshake (Z-score=2.0, P=0.05) at the six-hour timepoint.
  • Correlations between baseline TG concentration and peak TG value were significant in all four conditions. Baseline TG concentration was significantly correlated with TG AUC in the aspartame and glucose conditions.
  • Except with peak TG in the aspartame condition, BMI was not significantly associated with TG peak or AUC responses
  • Subjects rated the shakes as significantly different for sweetness (X=25.7, DF=3, P<0.0001), pleasantness (X=7.5, DF=3, P=0.05) and bitterness (X2=8.2, DF=3, P=0.04). All three shakes containing sweeteners were rated as significantly more sweet and more pleasant than the plain shake.
  • Although the sweetened shakes were equally sweet and were more palatable than the plain shake, the TG rise after the aspartame milkshake did not differ from the plain milkshake
  • Sensory questionnaires: For each session, there were no significant differences between treatments on ratings of saltiness, sourness, fattiness, oiliness or creaminess
  • Twenty-two subjects participated in the Harris-Kalmus and triangle tests. Only seven were able to distinguish between the aspartame and the fructose shakes during the triangle. No subjects could discriminate between the two with the Harris-Kalmus procedure.

Spearman Correlation Coefficents (P-Value) between baseline TG, Insulin, BMI and EPAT values and TG peak and AUC concentrations following treatments with sweetened and unsweetened milkshakes

  Peak Plain Peak ASP Peak GLU Peak FRU AUC Plain AUC ASP AUC GLU AUC Fru
TG 0.93 0.93 0.91 0.94 0.43 0.50 0.56 0.30
P-Value <0.001 <0.001 <0.001 <0.001 0.053 0.026 0.009 0.192
insulin 0.57 0.45 0.44 0.52 0.38 0.22 0.28 0.19
P-Value 0.009 0.052 0.044 0.015 0.097 0.356 0.215 0.415
BMI 0.39 0.51 0.29 0.43 0.29 0.33 0.09 0.10
P-Value 0.087 0.026 0.214 0.059 0.211 0.165 0.696 0.677
EPAT 0.06 0.11 0.22 0.27 0.32 0.02 0.10 0.20
P-Value 0.800 0.689 0.385 0.268 0.197 0.944 0.687 0.418
Author Conclusion:
The present data indicate that low levels of glucose and fructose consumed with lipid enhance post-prandial lipemia and that it does so at both the four-hour and six-hour time points. Sweetness and palatability did not account for the effect.
Funding Source:
Reviewer Comments:
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? ???
  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%.) N/A
  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? No
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? No
  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? N/A
  6.6. Were extra or unplanned treatments described? N/A
  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? 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)? Yes
  8.6. Was clinical significance as well as statistical significance reported? N/A
  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? No
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