EAL

DM: Omega-3 Fatty Acids (2014)

Citation:

Morgan WA, Raskin P, Rosenstock J. A comparison of fish oil or corn oil supplements in hyperlipidemic subjects with NIDDM. Diabetes Care, 1995; 18: 83-86.

PubMed ID: 7698053

Study Design:

Randomized Controlled Trial

Class:

A - Click here for explanation of classification scheme.

Quality Rating:

NEUTRAL: See Quality Criteria Checklist below.

Research Purpose:

To examine the effects on blood lipids and glycemic control of fish oil and corn oil supplementation at two levels in subjects with hyperlipidemia and non-insulin dependent diabetes mellitus (NIDDM).

Inclusion Criteria:

Diagnosis of NIDDM
Provided written informed consent
Plasma cholesterol over 5.17mmol per L
Plasma low-density lipoprotein cholesterol (LDL-C) over 3.36mmol per L
Plasma triglycerides (TG) over 6.47mmol per L.

Exclusion Criteria:

Not described

Description of Study Protocol:

Recruitment: Subjects with NIDDM were recruited
Design: Randomized controlled trial
Blinding used: Implied with measurements.

Intervention

Subjects were randomized to one of four treatments daily for 12 weeks:

Nine grams of fish oil capsules
18g of fish oil capsules
Nine grams of corn oil capsules
18g of corn oil capsules.

Statistical Analysis

All parameters were tested across time using a three-factorial analysis of variance with a repeated-measures factor
A Newman-Keuls multiple comparison test was used to identify significant interactions at the P<0.05 level.

Data Collection Summary:

Timing of Measurements

Measurements made at baseline, bi-weekly during four weeks of the baseline phase, bi-weekly until the end of the 12-week trial and for four weeks post-trial, for a total of 11 biweekly visits over 21 weeks.

Dependent Variables

Diabetes control was closely monitored with fasting plasma glucose (FPG)
Weight
Blood pressure
Blood lipids: Plasma total cholesterol, very-low-density lipoprotein cholesterol (VLDL), high-density lipoprotein cholesterol (HDL-C), LDL-C, VLDL triglycerides and total triglycerides.

Independent Variables

Subjects were randomized to one of four treatments daily for 12 weeks:

Nine grams of fish oil capsules
18g of fish oil capsules
Nine grams of corn oil capsules
18g of corn oil capsules.

Description of Actual Data Sample:

Initial N

40 subjects, 10 per group.

Attrition (Final N)

40 (18 men, 22 women)

Nine grams of fish oil: Four men, six women
18g of fish oil: Six men, four women
Nine grams corn oil: Four men, six women
18g of corn oil: Four men, six women.

Age

?Mean, 53.9±7.0 years.

Ethnicity

White: 24%
Black: 8%
Hispanic: 8%.

Other Relevant Remographics

Mean age at onset of NIDDM was 45.4±6.4 years.

Anthropometrics

There were no significant differences between the groups at baseline.

Location

Texas.

Summary of Results:

Key Findings

The level of oil supplements (nine grams per day compared with 18g per day) did not have significant effects on glycemic control and blood lipids with the fish oil and corn oil groups
When the nine-gram and 18-gram groups were combined, significant differences (P<0.05) in lipids were found
No significant differences were found among weight, FPG and HbA_1c between the treatment groups or across time
Plasma VLDL level was significantly lower (P=0.0001) in fish oil subjects, compared with corn oil subjects at 12 weeks of supplementation
There was a significant rise in plasma VLDL (P=0.04) in the corn oil subjects from Week Six to Week 12 of supplementation
Total plasma TG was significantly lower (P=0.0001) in the fish oil subjects compared with the corn oil subjects at six and 12 weeks of supplementation
Plasma VLDL-TG was significantly lower in the fish oil subjects compared with the corn oil subjects at six weeks (P=0.02) and at 12 weeks of supplementation (P=0.0001)
LDL-C was significantly higher in the fish oil subjects (P=0.008) at six weeks, but this difference disappeared at 12 weeks of supplementation. No significant differences were found in total plasma cholesterol or HDL-C.

Author Conclusion:

Fish oil supplementation improved plasma VLDL, VLDL TGs and total TGs, while having a transient deterioration in LDL-C in subjects in NIDDM
Furthermore, fish oil supplementation had no significant deleterious effect on glycemic control.

Funding Source:

University/Hospital:

Texas Women's University

Reviewer Comments:

Small numbers of subjects in groups.

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?		No
	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?	No
	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?	No
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?	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?	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?		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.)	Yes
	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)?	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?	No
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