Vegetarian Nutrition

VN: Micronutrients in Pregnancy (2007)

Citation:

Reddy S, Sanders TA, Obeid O. The influence of maternal vegetarian diet on essential fatty acid status of the newborn. Eur J Clin Nutr 1994;48:358-368

PubMed ID: 8055852
 
Study Design:
appears to be combination of data from two cross-sectional studies
Class:
D - Click here for explanation of classification scheme.
Quality Rating:
Neutral NEUTRAL: See Quality Criteria Checklist below.
Research Purpose:

To determine whether vegetarian maternal diet influences the essential fatty acid status of newborns and whether this is related to the outcome of pregnancy.

Inclusion Criteria:

Not reported

Exclusion Criteria:

Not reported.

Description of Study Protocol:

Recruitment

Women were randomly selected from two large General Practices in North London.

Design

  • Data on diet intake and fatty acid levels in vegetarian vs. omnivorous women, gathered from randomly selected samples of South Asian (of Indian descent) and white women from two large General Practices
  • These were non-pregnant women and it appears that this sample was different from the sample of pregnant women described below
  • Data on cord fatty acids and birth outcomes, gathered from cord samples and birth records of 146 deliveries at Northwick Park Hospital in Harrow, UK
  • Samples of vegetarian mothers and omnivorous mothers were paired for various characteristics (data on 27 pairs available).

Blinding Used

None.

Intervention

Not applicable.

Statistical Analysis

  • Comparison between non-pregnant vegetarians and omnivores by T-test
  • Paired T-test used to compare fatty acids
  • ANOVA used for other comparisons.
Data Collection Summary:

Timing of Measurements

  • Umbilical cord sample collected at birth (then frozen for analysis later)
  • Timing of maternal fasting venous blood sample from mothers not reported.

Dependent Variables

  • Birth weight, length, head circumference
  • Fatty acids composition of cord plasma in infants (from cord blood samples and umbilical cords).

Independent Variables

  • Arterial phospholipids in mothers
  • Maternal fat intake: Seven-day weighed food intake record.

Confounding Variables

  • Gestational age
  • Infant sex
  • Parity
  • Smoking habits
  • Maternal age
  • Maternal height.
Description of Actual Data Sample:

Initial N

Appears to be two data sources

  • 48 non-pregnant women (24 South Asian vegetarian, 24 white omnivores)
  • 48 pregnant South Asian vegetarian women and 98 pregnant white omnivores.

Attrition (Final N)

  • 32 pairs of subjects matched for maternal age, gestational age, parity and sex of infant were used to compare cord DHA levels
  • Complete data available on 27 pairs.

Mean Age

  • Vegetarians: 29
  • Omnivores: 28.4.

Ethnicity

  • South Asian
  • White.

Other Relevant Demographics

Owned homes and cars: Vegetarians: 88%; omnivores 66% and 63% (respectively).

Location

North London, UK.

Summary of Results:

linoleic acid: 18:2n-6

arachidonic acid (AA): 20:4n-6 (these give rise to prostaglandins)

docosapentaenoic acid: 22-5n-6

alpha linoleic acid: 18:3n-3

eicosapentanoic acid (EPA): 20:5n-3

docosahexaenoic acid (DHA): 22:6n-3

A high ratio of linoleic to alpha-linoleic acid leads to a decreased proportion of DHA in brain and retinal lipids--necessary for the development of the retina and brain. Dietary deficiency of alpha-linoleic acid results in lower DHA which may be replaced in retinal and brain lipids with docosapentaenoic acid which is derived from linoleic acid. Thus, dietary deficiency in alpha-linoleic acid causes adverse changes in visual function and learning ability.

Maternal Characteristics

  • Maternal height (p<.001) and weight (p<.05) were significantly lower in South Asian vegetarian women than white omnivores (at hospital booking).
  • Omnivores were more likely to be smokers than vegetarians (p<.01)

Maternal Dietary Intake

All contrasts listed below have a significance at p<.05 (and most p<.001).

  • Maternal height was lower in vegetarians than omnivores
  • Intakes of energy, fat, alcohol, and protein were significantly lower in vegetarians than omnivores
  • Proportion of dietary energy as carbohydrates and linoleic acid was greater in vegetarians than omnivores
  • Proportions of dietary energy as saturated fatty acid, AA, EPA, and DHA were lower in vegetarians than omnivores
  • The ratio of linoleic acid to alpha-linoleic acid was higher in vegetarians than omnivores
  • Proportion of linoleic acid in plasma phospholipids, plasma fatty acids, and free fatty acids was higher in vegetarians than omnivores
  • Proportion of EPA and DHA in in plasma phospholipids, plasma fatty acids, and free fatty acids were lower in vegetarians than omnivores

Fatty Acid Levels

Maternal

  • Proportion of docosapentaenoic acid was significantly greater (p<.001) in vegetarians than omnivores.
  • Proportions of DHA (p<.001) and palmitic (p<.02) acids were significantly lower in vegetarians than omnivores

Cord Levels

  • Total cord phospholipids were slightly higher (p<.05) in vegetarians than omnivores.
  • Fatty acids significantly lower in cord samples of vegetarians than omnivores (all p values <.05 or lower):
    • lauric
    • palmitic
    • stearic
    • oleic
    • DHA
  • Fatty acids significantly higher in cord samples of vegetarians than omnivores (all p values <.05 or lower):
    • eicosatrienoic
    • dihomogammalinoleic
    • arachidonic
    • docosapentaenoic

The difference between the ratios of eicosatrienoic/arachidonic acids was not significantly between vegetarians and omnivores.

Birth Outcomes

  • Early onset of labor (p<.02) and emergency Caesarean delivery (p<.05) were more common in vegetarians than in omnivores
  • After controlling for confounding factors:
    • Between group differences (vegetarian versus omnivores) had a larger effect on birth weight and head circumference than smoking
    • Between group differences (vegetarian versus omnivores) had a smaller effect on birth length than smoking
  • Mean birth weight, length, and head circumference differences (in 32 matched pairs: mean birth weight and head circumference significantly different (P<0.001)):
    • vegetarians: 3179g, 51cm, 34 cm (respectively)
    • omnivores: 3482g, 53cm, 34.7cm (respectively)

The proportion of DHA was not significantly associated with birth outcomes.

The ratio of eicosatrienoic/arachidonic acids was not significantly associated with birth outcomes.

Author Conclusion:

Vegetarians give birth to infants with less DHA in plasma and cord artery phospholipids. However, this did not appear to be independently related to birth outcomes. So, maternal intake of essential fatty acids did not appear to be the reason for lower birth weights of children of South Asian vegetarian women in the UK.

Funding Source:
University/Hospital: King's College
Reviewer Comments:

Strengths

Carefully designed comparison groups for cord fatty acids.

Weaknesses

  • small N
  • ethnicity was a confounder; would have liked to have seen a comparison of fatty acid levels between vegetarians and omnivores within ethnic groups
  • it appears that the data collected on vegetarian women versus omnivorous women was from a different sample than the data collected from umbilical cord samples
  • details on type of vegetarian diets not provided
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
  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
  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
  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
  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. Was the research question clearly stated? Yes
  1.1. Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified? 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
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated? Yes
  1.3. Were the target population and setting specified? Yes
  1.3. Were the target population and setting specified? Yes
  2. Was the selection of study subjects/patients free from bias? No
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
  2.1. 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
  2.2. Were criteria applied equally to all study groups? Yes
  2.3. Were health, demographics, and other characteristics of subjects described? No
  2.3. Were health, demographics, and other characteristics of subjects described? No
  2.4. Were the subjects/patients a representative sample of the relevant population? No
  2.4. Were the subjects/patients a representative sample of the relevant population? No
  3. Were study groups comparable? 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
  3.1. 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
  3.2. 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
  3.3. 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
  3.4. 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.) 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
  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? No
4. Was method of handling withdrawals described? No
  4.1. Were follow-up methods described and the same for all groups? N/A
  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%.) No
  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? No
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? No
  4.4. Were reasons for withdrawals similar across groups? No
  4.4. Were reasons for withdrawals similar across groups? No
  4.5. If diagnostic test, was decision to perform reference test not dependent on results of test under study? 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. 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? N/A
  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.) 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? No
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? No
  5.4. In case control study, was case definition explicit and case ascertainment not influenced by exposure status? 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
  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? No
6. Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described? No
  6.1. In RCT or other intervention trial, were protocols described for all regimens studied? 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? Yes
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? Yes
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? No
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? No
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? No
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? No
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? No
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? No
  6.6. Were extra or unplanned treatments 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
  6.7. 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
  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. 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
  7.1. Were primary and secondary endpoints described and relevant to the question? Yes
  7.2. Were nutrition measures appropriate to question and outcomes of concern? No
  7.2. Were nutrition measures appropriate to question and outcomes of concern? No
  7.3. Was the period of follow-up long enough for important outcome(s) to occur? 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
  7.4. 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
  7.5. 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
  7.6. Were other factors accounted for (measured) that could affect outcomes? Yes
  7.7. Were the measurements conducted consistently across groups? 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. 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
  8.1. 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
  8.2. 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
  8.3. 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
  8.4. 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
  8.5. 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
  8.6. 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
  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. Are conclusions supported by results with biases and limitations taken into consideration? Yes
  9.1. Is there a discussion of findings? Yes
  9.1. Is there a discussion of findings? Yes
  9.2. Are biases and study limitations identified and discussed? 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. Is bias due to study's funding or sponsorship unlikely? Yes
  10.1. Were sources of funding and investigators' affiliations described? No
  10.1. Were sources of funding and investigators' affiliations described? No
  10.2. Was the study free from apparent conflict of interest? Yes
  10.2. Was the study free from apparent conflict of interest? Yes