H/A: Dietary Intake (2007)

Citation:
 
Study Design:
Class:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:
To investigate the relation between dietary fatty acid intake and liver function in HIV-infected compared with HIV-uninfected subjects.
Inclusion Criteria:
  • Apparently healthy black volunteers aged more than 15 years
  • Asymptomatic HIV-infected and HIV-uninfected subjects.
Exclusion Criteria:
  • Pregnant and lactating women
  • Known diagnosed diseases
  • Use of chronic medications
  • Oral temperatures over 37 degrees Celsius
  • Inebriated subjects.
Description of Study Protocol:
  • Recruitment: Recruited from 37 randomly-selected sites throughout the North West province of South Africa in 1996 and 1998
  • Design: Cross-sectional epidemiological survey.

Statistical Analysis

  • Data are presented as adjusted means (95% CIs) for HIV-infected and HIV-uninfected subjects
  • Data that were not normally distributed were normalized by logarithmic transformations
  • Multivariate analysis was used to compare biochemical variables of HIV-infected and HIV-uninfected subjects
  • Partial correlations were used to determine the associations between the intake of dietary fat and vitamin E and the biochemical variables
  • Fisher Z-values were calculated for each correlation to test for significant differences in R-values between HIV-infected and uninfected subjects.
Data Collection Summary:

Timing of Measurements

Measurements made and compared.

Dependent Variables

  • BMI
  • Blood pressure
  • Fasting blood samples analyzed for serum protein, albumin, globulin, gamma-glutamyl transpeptidase, alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, lactate dehydrogenase and lipids
  • HIV status.

Independent Variables

Demographic information, physical activity and dietary intake data were obtained during individual interviews by using validated questionnaires.

Control Variables

  • Level of urbanization
  • Age
  • Sex
  • Year of study
  • Alcohol intake.
Description of Actual Data Sample:
  • Initial N: 1,854 healthy black volunteers. Complete data available for 216 asymptomatic HIV-infected (96 male, 120 female) and 1,604 HIV-uninfected subjects (685 male, 920 female)
  • Attrition (final N): As above
  • Age: HIV-infected subjects' mean age, 34.8 years; uninfected subjects' mean age, 37.9 years
  • Ethnicity: All were black
  • Other relevant demographics: HIV-infected subjects' mean BMI, 23.7; uninfected subjects' mean BMI, 24.0
  • Location: South Africa.

 

Summary of Results:

Liver Enzymes

HIV Infected

HIV Uninfected

P2

GGT 44.1 (29.3, 58.8) 39.2 (32.9, 45.6)

NS

ALT

16.8 (14.0, 19.5)

13.4 (12.2, 14.6)

0.03

AST

37.0 (28.6, 45.4)

24.3 (20.7, 28.0)

0.01

ALP 79.4 (74.3, 84.5) 77.4 (75.5, 79.3) NS
LDH 148.0 (142.6, 153.3) 138.9 (136.6, 141.2) <0.01

Other Findings

  • Concentrations of total serum protein and globulin were significantly higher, whereas concentrations of total serum cholesterol, HDL cholesterol and albumin were significantly lower in HIV-infected subjects than in uninfected subjects
  • Alcohol intake tended to be higher in HIV-infected subjects (P=0.08)
  • HIV-infected and uninfected subjects did not differ significantly with regard to BMI, education, smoking or snuff-taking, blood pressure and physical activity
  • Intakes of polyunsaturated fatty acids, linoleic acid (n-6) and the ratio of PUFAs to saturated fatty acids were positively associated with all the liver enzymes measured in HIV-infected subjects (R=0.16-0.65).
  • Most of these R-values differed significantly from the R-values for HIV-uninfected subjects
  • No associations were seen between liver enzymes and intakes of SFAs and monounsaturated fatty acids
  • Vitamin E intake was positively associated with serum-gamma-glutamyl transpeptidase (R=0.23), alanine aminotransferase (R=0.37) and aspartate aminotransferase (R=0.58) in HIV-infected subjects. These correlations differed significantly from those of the HIV-uninfected subjects because PUFA sources are the main carriers of vitamin E.
Author Conclusion:
The main observation of this investigation was that the n-6 PUFA intake was adversely related to liver function in asymptomatic HIV-infected subjects, compared with HIV-infected subjects. The reasons or mechanisms responsible are not clear and further research is necessary to determine the optimal safe amounts for intake of n-6 PUFAs by HIV-infected subjects, especially in countries with traditionally high intakes of n-6 PUFA-rich vegetable oils.
Funding Source:
Government: National Research Foundation (South Africa), SA MRC
Industry:
South African Sugar Association, Dry Bean Producers Organization
Commodity Group:
University/Hospital: North-West University
Reviewer Comments:
Authors note that since HIV-infected subjects were apparently healthy and asymptomatic, the early stage of HIV infection resulted in absence of significant differences between HIV-infected and uninfected individuals in some parameters.
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) N/A
  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) N/A
 
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) N/A
  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? 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.) Yes
  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? 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.) 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? N/A
  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? 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? N/A
  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? 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