DLM: Elevated Triglycerides and Omega-3 Fatty Acids (2007)

Citation:
 
Study Design:
Class:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:
To evaluate the lipid responses in mildly hypertriglyceridemic men and women to consumption of DHA-enriched chicken eggs compared to consumption of ordinary (non-enriched) chicken eggs.
Inclusion Criteria:
Males and Females between 21 and 80 years of age with triglyceride between 140 amd 450 mg/dL and total cholesterol levels < 300 mg/dL.

Participants had to be willing to abstain from all eggs other than those provided, restrict alcohol for 48 hours prior to each clinic visit, and maintain body weight and usual level of physical activity.
Exclusion Criteria:

Participants were excluded for known allergy to eggs, BMI > 38 kg/m2 , use of cyclic hormone replacement therapy or oral contraceptives within eight weeks of the preliminary screening (week -2).

Pregnancy, use of hypolipidemic therapy including: flaxseed oil, fish oil supplements or other omega-3 fatty acid supplements, niacin or its analogues at doses > 400 mg/day, and dietary fiber supplements within four weeks of preliminary screening (week -2).
Exclusionary Medications included: drugs for regulating homeostasis (expect stable dose aspirin), systemic corticosteroids, androgens, phenytoin, erythromycin, and thyroid hormone (except stable dose replacement therapy) for >/= 2 months prior to enrollment.
Poorly controlled  hypertension, diabetes mellitus,; Type I, III, IV, V, or secondary dyslipidemia, history of cancer within the previous five years, curent or recent history of significant atherosclerotic, gastrointestinal, hepatic, pulmonary, endocrine, or renal disease, and recent history or strong potential for substance abuse.

Description of Study Protocol:

Participants for this 8 week randomized double blind study were recruited from  the Chicago metropolitan area and pre-selected by telelphone, eligability was further assessed at screening visits weeks -2 and -1.

Pre-screening:
     Week -2: Vital signs, weight, and serum lipid profile
     Week -1: serum chemistry, hematology, urinalysis panels and a wrine pregnancy test (for women of childbearing potential), 3 day diet record

Intervention Period:

Week 0 (baseline): physical examination, analysis of lipoprotein subfractions, serum levels of DHA and EPA, Stanford 7-Day Physical Activity Recall Questionnaire, 3 day diet record.

  • Subjects were randomized at baseline visit into one of two groups: eggs from chickens that recieved DHA-enriched feed (147 mg DHA/egg) or eggs from chickens that did not recieve DHA-enriched feed (20 mg DHA/egg) ordinary egg treatment).    
  • Daily, each subject received about 29 mg DHA/day with the ordinary egg treatment and 209 mg DHA/day with the DHA-enriched eggs.
  • Subjects were instructed to continue following usual diets, but subsituting 10 eggs per week (DHA- enriched or ordinary) for similar foods (high protein, low carbohydrate foods). Also instructed not to consume any whole eggs other than those provided.
  • Provided with cooking spray and recipes for cooking eggs. Received fresh eggs weekly.

Weeks 3,5, and 6: Participants returned to clinic for serum lipids profile and assessments of body weight, vital signs, concomitant medication use, adverse events, recorded information specific to unusual or vigoruos activity with 48 hours of clinic visit.

Week 5: Diet records were dispensed, collected, and analyzed at week 6.  

Week 6: Serum chemistry panel, assessments of lipoprotein subfractions, serum levels of EPA and DHA, repeat urine pregnany test for all women of child bearing potential, and participants completed the Stanford 7-Day Physical Activity Recall questionnaire.

Statistical Analysis

 Statistical analysis was preformed for both intent to treat (all subjects who completed at least one clinic visit) and per protocal (all subjects >/=80% compliance). Baseline comparability of treatments for demographic, anthropometric, and lipid values was assessed using analysis of variance, chi-square test. Parametric and non-parametric analyses measured comparison  treatments for responses.  Incidence of adverse effects was measured with Fisher's exact (2-tail) test.

Data Collection Summary:

Urinalysis (Clinitek Atlas), serum chemistry (Hitachi 747), hematology (Coulter STKS) and lipid profile (CDCP standardized fasting lipid profile).

Cholesterol, TG, HDL-C, LDL-C (Friedewald equation), and non-HDL-C (for subjects with TG>400 mg/dL). assesments of plasma lipoprotein subfractions, serum DHA and EPA. 

Dietary Assessment: energy (kcal), % energy from: CHO, PRO, FAT (total, saturated, mono- and poly- unsaturated fat, total omega-3 fatty acids, DHA, EPA, and alcohol. Cholesterol (mg/dL) and dietary fiber (g/day).

Description of Actual Data Sample:

410 people initially screened and 153 subjects(107 males, 46 females) identified. 3 subjucts dropped from the study proir to completion of the intervention period. Total of 150 participants comlpleted the study.

Subjects demographic and baseline characteristics showed no significant difference  between treatments in sex, race, age, height, weight, BMI, blood pressure, or activity score. Mean Ht: 171 cm, Mean wt: 86 kg. Mean age ~ 54 years and mean BMI ~29 kg/m. The majority of subjects (~72%) were Non-hispanic white and ~79% of subjects were male.  Mean activity score ~216 metabolic equivalent-hours/week.

Baseline lipids
DHA grp (mg/dL): TG 210, TC 234, HDL 44, LDL 135
Control grp: TG 205, TC 228, HDL 185, LDL 140 (no stat diff between grps)

Reported mean compliance of the study exceeded 99% for both the DHA-enriched and ordinary egg treatments.  Study was completed in the Chicago metro area.

 

 

Summary of Results:

There was not a significant difference between the treatments in percent change from baseline of total, HDL-C, non-HDL-C, or TG  Median LDL-C increased significantly with the DHA-enriched egg treatment (5.9%) as compared to the ordinary egg treatment. (2.3%) p=0.047.

For subjects with BMI< 30 kg/m2 , there was no significant difference between treatments in serum lipids from baseline to end of treatment.

For subjects with BMI >/= 30 kg/m2,  there was not a significant difference in total cholesterol, non-HDL-C, or LDL-C. However, serum TG level decreased significantly in the DHA-enriched egg treatment as well as a significant increases in HDL-C and median LDL-C levels with the DHA-enriched egg treatment. Noted: after adjustment for baseline TG, treatment effects for percent changed from baseline to the end of treatment for subjects were not significant for any lipid parameters.

 Percent Changes from baseline to the end of treatment in serum lipid paramenteres for subjects with BMI <30 kg/m2 and BMI>/=30 kg/m2

Parameter

(mg/dL)

DHA-Enriched Eggs

(% change)

Ordinary Eggs

(% chagne)

Statistical Significance of Group Difference

Triglycerides

BMI<30 kg/m2

BMI>/= 30kg/m2

 

-6.90 (-45.34, 58.24)b

-12.31 (-69.51,23.84)ab

 

-8.79(-59.25, 56.30)b

2.07(.51.56,36.62

 median given for TG

ap<0.05 vs ordinary eggs                bp<0.05 vs. basline

Total cholesterol

BMI<30 kg/m2

BMI>/= 30kg/m2

 

2.0 +/-1.2

2.5 +/- 1.5

 

0.3 +/- 1.2

0.7 +/- 1.6

 

HDL-C

BMI<30 kg/m2

BMI>/= 30kg/m2

 

3.2 +/- 1.3b

5.0 +/- 1.5ab

 

5.4 +/- 1.4b

1.1 +/- 1.2

 

Non-HDL-C

BMI<30 kg/m2

BMI>/= 30kg/m2

 

1.5+/-1.4

1.9 +/-1.8

 

-0.9 +/- 1.5

0.5+/-2.0

 

LDL-C

BMI<30 kg/m2

BMI>/= 30kg/m2

 

4.2 +/- 1.7b

12.4 +/- 4.2ab

 

2.2+/-1.7

2.5+/-2.2

 

 

Other Findings

 There was no significant difference between DHA-enriched eggs and ordinary egg treatments in the percent change from baseline for serum EPA concentration, however serum DHA cocentration increased 41.2% from baseline in the DHA-enriched group and decreased 0.9% in the ordinary egg treatment (P<0.001).

Overall there was not a significant difference between the 2 groups in lipoprotein subfractions for subjects with BMI< 30 kg/m2. However, subjects with BMI >/= 30 kg/m2, there was a decrease in change from baseline for small LDL-C particles in the DHA-enriched egg treatment. There was an increase in LDL-C carried by medium plus large subfractions in the the DHA-enriched egg treatment.

Author Conclusion:

Overall, this study found no triglyceride lowering or HDL-C raising effects of DHA-enriched (~209 mg DHA/day) eggs when compared to ordinary eggs. (decrease 8.7% vs 5.1% respectively). HDL-C concentrations were increased 3.7 % in both treatments. Possible reasons for lack of effect on TG and HDL-C levels could be attributed to the low dose of DHA provided and the short length of time the study was conducted.  LDL-C increases may be attributed to increase in particle size vs. actual number of LDL-C molecules. This study did find that DHA-enriched egg has a favorable effect on TG and HDL-C concentrations in subjects with BMI>/= 30 kg/m2. Possible explanations for TG lowering effects of DHA in obese subject is the elevated VLDL production normally seen in obese people, and may be more responsive to inhibition by omega-3 fatty acids than among those who are lean. Another plausible explanation  on the TG lowering effect of DHA-enriched eggs is partly attributable to differences between treatments at baseline TG since adjustment  for baseline TG concentrations reduced the treatment effects for TG and HDL-C to marginal significance.

Funding Source:
Reviewer Comments:
Author does note that while this particular study did not show TG lowering or HDL-C raising effects of DHA supplementation, the dose provided in the study was significantly smaller than dosed used in previous studies. Also, the authors notes that to their knowledge this was that first study to compare the lipid lowering effects of omega-3 fatty acid supplementation in obese vs. non-obese subjects. 
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? 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%.) No
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? Yes
  4.4. Were reasons for withdrawals similar across groups? ???
  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? ???
  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? ???
  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? 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? 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)? Yes
  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