Vegetarian Nutrition

VN: Micronutrients in Pregnancy (2007)

Citation:

Ellis R, Kelsay JL, Reynolds RD, Morris ER, Moser PB, Frazier CW. Phytate:zinc and phytate X calcium:zinc millimolar ratios in self-selected diets of Americans, Asian Indians, and Nepalese. J Am Diet Assoc. 1987 Aug;87(8):1043-7.

PubMed ID: 3611550
 
Study Design:
Panel
Class:
C - Click here for explanation of classification scheme.
Quality Rating:
Neutral NEUTRAL: See Quality Criteria Checklist below.
Research Purpose:
To determine the phytate:zinc and phytateXcalcium:zinc millimolar ratios of self-selected diets of American omnivores and lacto-ovo vegetarians, Asian Indian immigrnt lacto-ovo vegetarians, and Nepalese lactating vegetarians.
Inclusion Criteria:

Study 1: 29 omnivorous subjects

Study 2:  53 adult lacto-ovo vegetarians living in the Washington, DC suburbs.  Subjects were 30 Asian Indians and 23 Americans

Study 3:  26 lactating vegetarians (22 vegan and 4 lacto-ovo) mothers living in six villages outside of Kathmandu.

No other inclusion criteria provided.

Exclusion Criteria:
No other exclusion criteria provided.
Description of Study Protocol:

Recruitment -- None stated

Design

Study 1: Subjects completed daily dietary records of all foods and beverages consumed for 365 days. Once every season, subjects collected duplicate food and beverage samples for 1 week.  Samples were collected in trace metal-free containers.  Each days food was blended and aliquots for each of the 7 days were combined and bended into one compostie.  Aliquots of the total were lyophilized and analyzed for phytate and minerals.

Study 2:  Subjects kept detailed dietary intake records for 14 days.  During the second 7 days, they were asked to eat the same foods they ate during the first 7 days and to collect duplicate amounts of all foods and beverages.  The diet composites were homogenized, lyophilized, and analyzed as decribed in Study 1.

Study 3:  All subjects were 2-6 months postpartum and each had given birth to a single child.  Each subject collected a duplicate compsite of all foods onsumed with a 24 hour period.  Composites were homogenized, and aliquots were forzen for shipment back to the US where they were lyophilized and analyzed for phytate, minerals, and other nutrients.

Blinding used (if applicable) NA

Intervention (if applicable) NA

Statistical Analysis

Mean values of phytate, zinc, and calcium were compared amount the groups.

Diets analyzed for the following components expressed as mmol / day

  • phytate:zinc
  • phytate X calcium: zinc

Means of these values were also compared among the groups.

Data Collection Summary:

Timing of Measurements

Study 1:  Foods collected and samples analyzed once per quarter

Study 2:  Foods collected for 7 days and samples analyzed.

Study 3:  Foods collected for 24 hours and samples analyzed.

Dependent Variables

  • zinc, phytate, and calcium levels in each food

Independent Variables

  • self-selected diets (both omnivorous or vegetarian)

Control Variables

  •  sex
  • race/ethnicity
Description of Actual Data Sample:

Initial N:

Study 1: 29 American omnivores (16 women and 13 men)

Study 2: 53 adult lacto-ovo vegetarians; 30 Asian Indians(13 women and 17 men) and 23 Americans (12 women and 11 men)

Study 3: 26 lactating vegetarians (22 vegan and 4 lacto-ovo vegetarians)

Attrition (final N): NA

Race/Ethnicity: American, Asian Indian, Nepalese

Age: adults

Location: USA, Nepal

Summary of Results:

Phytate

  • The mean daily phytate intakes of vegetarian subjects were greater than the phytate intakes of subjects consuming omnivorous diets
  • The lactating Nepalese women had the highest daily phytate intake of any group
  • There were not significant seasonal effects on the phytate intakes of the men consuming the omnivorous diets
  • The women consumed significantly more phytate during the winter than during any of the other seasons

Zinc

  • Zinc intakes of American omnivores and American vegetarians were comparable
  • Daily zinc intakes of both American groups were significantly higher than those of Asian Indian vegetarians
  • Mean intake of zinc in all groups was less than the RDA

Calcium

  • Calcium of American omnivorous and American vegetarian subjects were similar
  • Calcium intakes by American men were significantly higher than those of Asian Indian men
  • Calcium intakes of American women were only lslightly higher than those of Asian Indian women
  • Calcium level of Nepalese diets was the lowest of all diets
  • Calcium intakes for male subjects were higher than those of corresponding female subjects

Phytate:Zinc molar ratios

  • Overall ranges of the phytate:zinc molar ratio of the diets were
    • American omnivorous (women, 5:12; men 4:9)
    • American vegetarians (women, 8:21; men 9:23)
    • Asian Indian vegetarians (women 7:17; men 5:20)
    • Female Mepalese vegetarians (9:23)
  • Men had higher daily phytate intakes than wmen, the women had slightly higher phytate:zinc molar ratios (as a result of the women’s lower zinc intakes)

Phytate x Calcium:Zinc millimolar ratio

  • Overall ranges of phytate x calcium:zinc ratio of the diets were
    • American omnivorous (women 69:211; men 57:414)
    • American vegetarians (women 91:434; men 145:548)
    • Asian Indian vegetarians (women 127:319; men 123:405)
    • Female Nepalese vegetarians (54:533)
  • The mean ratios for men are slightly higher than those for women, due to the higher calcium intakes by men

As expected, both mean phytate:zinc and phytateXcalcium:zinc millimolar ratios of vegetarian self-selected diets were greater than those of omnivorous diets

Comparison of phytate:zinc and phytate X calcium: zinc millimolar ratios above critical level*

 

Diet

Phytate:Zinc

Phytate X Calcium:Zinc

 

Females

Males

Females

Males

 

%**

No.***

%

No.

%

No.

%

No.

Omnivorous (US)

6

16

0

13

11

16

31

13

Vegetarian (US)

83

12

82

11

66

12

91

11

Vegetarian (Asian Indian)

85

13

76

17

46

13

71

17

Vegetarian (Nepalese)

96

26

 

 

58

26

 

 

*Suggested critical level for phytate:zinc and phytate x calcium:zinc molar ratios are >10 and >200, respectively

**Percent above critical level

***No of subjects.

 

 

 

Author Conclusion:

If the data from animal studies and the retrospective calculations by Bindra et al (Nutr Res 6:475, 1986) are applicable to the human diet in general, the present study suggests phytate is probably of minor importance in affecting the zinc status of most of the US population.

The results do indicate that long-term vegetarians may be at risk for imparied zinc bioavailability if they consume a large amount of high calcium products.

In contrast, the phytate X calcium:zinc millimolar ratio suggests that vegetarians might consume a high phytate, low-calcium diet, such as that of Nepalese vegetarians, with relatively little phytate effect on the bioavailability of the dieteray zinc.

Funding Source:
Government: USDA Beltsville Human Nutrition Research center
University/Hospital: University of Maryland
Reviewer Comments:

Strengths:

  • Able to show statistical significance not only of specific mineral intakes but, more importantly, how phytate intake relates to the mineral intake of various diets (omnivore and vegetarian) of men and women

Weakness:

  • Small groups among the varied diet types
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? N/A
  3. Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice? N/A
  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? ???
2. Was the selection of study subjects/patients free from bias? ???
  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? 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
  2.4. Were the subjects/patients a representative sample of the relevant population? Yes
  3. Were study groups comparable? ???
3. Were study groups comparable? ???
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) ???
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) ???
  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.) N/A
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) N/A
  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
  3.4. 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
  3.5. 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? ???
4. Was method of handling withdrawals described? ???
  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%.) 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%.) N/A
  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? N/A
  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
  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? N/A
5. Was blinding used to prevent introduction of bias? N/A
  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.) ???
  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.) ???
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? N/A
  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
  5.4. 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? Yes
  5.5. In diagnostic study, were test results blinded to patient history and other test results? Yes
  6. Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described? ???
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? 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? No
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? No
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? 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
  6.4. 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
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? N/A
  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? Yes
  6.8. In diagnostic study, were details of test administration and replication sufficient? Yes
  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? 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? N/A
  7.5. Was the measurement of effect at an appropriate level of precision? N/A
  7.6. Were other factors accounted for (measured) that could affect outcomes? N/A
  7.6. Were other factors accounted for (measured) that could affect outcomes? N/A
  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)? N/A
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? N/A
  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