Vegetarian Nutrition

VN: Micronutrients in Pregnancy (2007)

Citation:

Drake R, Reddy S, Davies J. Nutrient intake during pregnancy and pregnancy outcome of lacto-ovo-vegetarians, fish-eaters and non-vegetarians. Veg Nutr. 1998; 2: 45-52.

 
Study Design:
Longitudinal study
Class:
C - Click here for explanation of classification scheme.
Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:
To compare maternal nutrient intake and pregnancy outcomes of women of the same ethnic origin and different patterns of meat consumption.
Inclusion Criteria:
  • Caucasian
  • Over 18 years old
  • Primiparous
  • Free from medical conditions that might affect mother or infant nutrition
  • Consistent meat consumption pattern for at least two years.
Exclusion Criteria:
  • Vegans
  • People who described themselves as semi- or demi-vegetarians.
Description of Study Protocol:

Recruitment

Recruited via media (magazines, newspapers, fliers in health food shops and cafes and with the assistance of midwives).

Design

Three comparison groups:

  • Ovolactovegetarians (exclude all meat but include dairy and egg products in their diets)
  • Fish eaters (add fish to an otherwise ovolactovegetarian diet)
  • Omnivores.

Blinding Used

None.

Statistical Analysis

  • Chi-square for frequency data
  • ANOVA for each nutrient
  • Duncan multiple-range test for multiple comparisons.
Data Collection Summary:

Timing of Measurements

  • First questionnaire during pregnancy and second questionnaire after delivery
  • Questionnaires were developed from interviews with nine women and then piloted with 11 women, including sex, from the questionnaire development interviews.

Dependent Variables

  • Diet and cravings: Three-day dietary intake questionnaire (two weekdays and one weekend day), including portion estimates. Reported energy intake validated by computing a ratio between reported energy intake and estimated BMR.
  • Health during pregnancy: Questionnaire
  • Satisfaction with dietary instruction during pregnancy
  • Birth details: Questionnaire.

Independent Variables

 Diet group.

Confounding Variables

  • Trimester
  • Gestational age
  • Maternal height
  • Sex of infant.
Description of Actual Data Sample:

Initial N

Of 162 respondents, 132 met inclusion criteria.

Attrition (Final N)

  • Two vegetarians who smoked were excluded from the multiple comparison analysis
  • Final N=114 (18 diet records were dropped because they were incomplete)
    • Ovolactovegetarians: 31
    • Fish eaters: 14
    • Omnivores: 69.

Mean Age

  • Ovolactovegetarians: 25 years
  • Fish eaters: 29.9 years
  • Omnivores: 29.8 years.

Ethnicity

Caucasian.

Other Relevant Demographics

  • Over 90% of respondents were from a non-manual labor class
  • 60% were educated to a degree level (fish eaters had a slightly higher level of education)
  • Two-thirds of each group reported exercising regularly
  • Less than one-third reported using alcohol
  • Only two vegetarian respondents reported smoking
  • Age, pre-pregnancy BMI and week of pregnancy were similar in each group
  • Median time on ovolactovegetarian diet: Eight years
  • Median time on fish-eating diet: Nine years.

Location

UK.

Summary of Results:

Cravings

  • No differences between groups in the incidence of cravings or aversions, though more ovolactovegetarians reported craving salty foods, while fish eaters and omnivores tended to crave fruits and sweet foods
  • Diet adaptations to nausea were similar across groups.

Diet Information During Pregnancy

  • Most women obtained diet information and advice from books, magazines and Department of Health publications
  • Ovolactovegetarians were significantly less likely to obtain information from family members or the above sources and more likely to get information from supermarket fliers, the Vegetarian Society and National Childbirth Trust
  • Ovolactovegetarians reported finding the most useful information from books written specifically for vegetarians. Fish eaters did not find these books helpful.
  • Some fish eaters and omnivores report obtaining useful dietary information from midwives or general practitioners, however none of the vegetarians found these sources of information useful
  • Significantly more (P<0.05) vegetarians reported dissatisfaction with the information available to them during pregnancy than women in other diet groups.

Nutrient Intake

  • Macronutrients
    • No significant differences between groups in energy intake
    • Ovolactovegetarians and fish eaters consumed significantly more carbohydrates and less protein (as a percentage of energy intake) than omnivores
    • All groups consumed similar amounts of fat, saturated fat and alcohol
    • Fish eaters had a significantly higher intake of non-starch polysaccharides than either of the other diet groups.
  • Micronutrients
    • Intakes of Ca, folate and vitamin C were significantly lower in ovolactovegetarians and fish eaters than in omnivores
    • Ovolactovegetarians had a significantly lower intake of B12 than the other groups
    • Ovolactovegetarians had a significantly lower zinc intake than omnivores
    • Dietary iron was similar across groups.

Dietary Supplements

  • The following percentages of the different diet groups reported taking dietary supplements in their three-day food records
    • Ovolactovegetarians: 52%
    • Fish eaters: 50%
    • Omnivores: 35%.
  • The most common supplements were folic acid, combined iron and folic acid and multi-vitamins
  • When supplement intakes were factored into the analysis, differences in folate and zinc intakes among groups disappeared, however significant differences in the intake of Ca, vitamin B12 and vitamin C remained
  • The mean intake of micronutrients for all groups met the Reference Nutrient Intakes (RNI) for all micronutrients, except iron. Although ovolactovegetarian intakes of zinc and B12 were above the RNI, they were still significantly lower than the intake of omnivores
  • Estimated average requirement (EAR) for zinc (5.5 micrograms per day) was not met by 16% of ovolactovegetarians and 4% of omnivores
  • EAR for vitamin B12 (1.25 micrograms per day) was not met by 10% of ovolactovegetarians, but was met by all members of other diet groups.

Pregnancy Outcome

  • 126 women completed the post-pregnancy questionnaire
  • There were no significant differences in any pregnancy outcomes between groups.
Author Conclusion:

Vegetarian women should be reassured that vegetarian diets can be adequate for pregnancy, however vegetarian women and fish eaters may benefit from specifically targeted advice concerning iron, zinc and vitamin B12.

Funding Source:
University/Hospital: St. Mary's, South Bank University (UK)
Reviewer Comments:

 

  • Strengths: Well-designed and executed study
  • Weaknesses: Small N for vegetarian and fish-eater 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) 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? 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
  2.1. 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
  2.2. Were criteria applied equally to all study groups? Yes
  2.3. Were health, demographics, and other characteristics of subjects described? 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
  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? Yes
4. Was method of handling withdrawals described? Yes
  4.1. Were follow-up methods described and the same for all groups? 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
  4.2. 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
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? Yes
  4.4. Were reasons for withdrawals similar across groups? 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
  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? Yes
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
  6.1. 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? 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
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? Yes
  6.6. Were extra or unplanned treatments 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? 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
  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? 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
  7.3. 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
  7.4. 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? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.2. Was the study free from apparent conflict of interest? Yes
  10.2. Was the study free from apparent conflict of interest? Yes