EAL

Disorders of Lipid Metabolism and Carbohydrates

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

Determine the effects of consumption of varying amounts of palm oil and dietary cholesterol on blood lipids in healthy male subjects.

Inclusion Criteria:

Informed consent
No evidence of physical or psychiatric disease
Normal blood pressure, fasting glycemia and blood coagulation tests
Access to the university cafeteria

Exclusion Criteria:

Not meeting inclusion criteria

Description of Study Protocol:

Double-blind 4x4 dietary crossover trial. Subjects randomly assigned to 1 of 4 diet sequences (n=7 per group) where subjects consumed each diet for a 4 week period. The diets are described below.

High palm oil, low cholesterol (HPOLC)
High palm oil, high cholesterol (HPOHC)
Moderate palm oil, moderate cholesterol (HPOMC)
Low palm oil, moderate cholesterol (LPOMC)

Palmitic Acid and Cholesterol Content of Diets

	DPA* (%)	DC* (mg/kJ)
HPOLC	8.8	181
HPOHC	8.8	866
HPOMC	6.3	581
LPOMC	Negligible	543

*DPA: Dietary palmitic acid, DC: dietary cholesterol

Subjects consumed all meals prepared by researchers at university cafeteria 7 days/week. Any foods outside of protocol were to be recorded by participants. Researchers kept daily compliance record throughout study.

Data Collection Summary:

Last week of each diet period

Weight, BP, 3-12 hr fasting blood sample drawn on consecutive days.

Blood sample analysis

Total cholesterol (TC), LDL, HDL, triglycerides (TG)

Blinding: Laboratory personnel were blinded to the type of diet the subject was on when analyzing blood samples.

Description of Actual Data Sample:

N=28 healthy male students

Mean age 24.6 (range 20-34 y)
Mean weight 62.0 kg
N=1 had TC > 6.21 mmol/L
N=8 had TC between 5.17 and 6.21 mmol/L

100% participant retention.

Summary of Results:

Baseline Lipid Concentrations, Mean (95% CI) mmol/

TC: 4.80 (4.5, 5.11)
LDL: 3.35 (3.09, 3.62)
HDL: 0.93 (0.86, 1.01)

Change in Plasma Lipids w/Changes in Dietary Cholesterol and Palmitic Acid

Diet Contrast	Lipid	?mmol/L	P-value
High vs. Low Cholesterol	TC	0.21	0.009
	LDL	0.16	0.047
	HDL	0.03	0.095
High vs. Low Palm Oil	TC	0.39	<0.001
	LDL	0.38	<0.001
	HDL	0.03	0.097

Increasing DC resulted in a significant rise in LDL, mean 0.16 mmol/L (95% CI 0.002, 0.32; p=0.047).
Increasing DPA resulted in a significant rise in LDL, mean 0.38 mmol/L (95% CI 0.21, 0.55; p<0.001).

Miscellaneous:

After randomization, 4-diet sequence groups not statistically different for age, weight, or outcome variables.

DC and DPA effects on blood lipoprotein were independent of diet sequence (p=0.24).

Participants consumed 90% of all meals provided in the study and compliance similar in 4-diet sequence groups.

Author Conclusion:

Non-extreme short term changes in DPA and DC consumption lead to significant elevations in plasma TC and LDL-C.

Extrapolation of our results to long-term effects is compromised because each diet lasted only one month.

Restriction in the consumption of palm oil and eggs in subjects at high risk of coronary heart disease may be advisable.

Funding Source:

University/Hospital:

Univormed Services University of the Health Science, University of Alberta (Canada), Fundación Cardiovascular del Oriente Colombiano (Columbia)

Reviewer Comments:

Unknown weight classification of subjects. Mean height nor BMI data were reported for subjects.

No wash out period was done between diet treatments. This might have caused a type of carry-over effect where blood lipid levels could have been affected by the previous diet treatment.

No inclusion/exclusion criteria for hypercholesterolemia. Initial cholesterol values of participants (n=9 w/TC > 200 mg/dL) could impact response to diet treatments and limit generalizability.

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?	N/A
	1.2.	Was (were) the outcome(s) [dependent variable(s)] clearly indicated?	N/A
	1.3.	Were the target population and setting specified?	N/A
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?	N/A
	2.2.	Were criteria applied equally to all study groups?	N/A
	2.3.	Were health, demographics, and other characteristics of subjects described?	N/A
	2.4.	Were the subjects/patients a representative sample of the relevant population?	N/A
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)	N/A
	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?	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?	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?	N/A
	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.)	N/A
	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?	N/A
	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?	N/A
	6.4.	Was the amount of exposure and, if relevant, subject/patient compliance measured?	N/A
	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?	N/A
	7.2.	Were nutrition measures appropriate to question and outcomes of concern?	N/A
	7.3.	Was the period of follow-up long enough for important outcome(s) to occur?	N/A
	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?		No
	8.1.	Were statistical analyses adequately described and the results reported appropriately?	N/A
	8.2.	Were correct statistical tests used and assumptions of test not violated?	N/A
	8.3.	Were statistics reported with levels of significance and/or confidence intervals?	N/A
	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?	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?	N/A
	9.2.	Are biases and study limitations identified and discussed?	N/A
10.	Is bias due to study's funding or sponsorship unlikely?		???
	10.1.	Were sources of funding and investigators' affiliations described?	N/A
	10.2.	Was the study free from apparent conflict of interest?	N/A