Vegetarian Nutrition

VN: Vitamin B-12 (2011)

Citation:

Miller DR, Specker BL, Ho ML, Norman EJ. Vitamin B-12 status in a macrobiotic community. Am J Clin Nutr. 1991; 53: 524-529.

PubMed ID: 1989421
 
Study Design:
Cross-Sectional Study
Class:
D - Click here for explanation of classification scheme.
Quality Rating:
Neutral NEUTRAL: See Quality Criteria Checklist below.
Research Purpose:

To determine the vitamin B12 status in members of a macrobiotic community and to determine whether vitamin B12 status correlates with the intake of certain foods in a vegetarian diet that may contain vitamin B12.

Inclusion Criteria:

Adults and children following a macrobiotic diet in two macrobiotic communities; one in Boston, MA and the other in Middletown, CT. 

Exclusion Criteria:

None reported.

Description of Study Protocol:

Recruitment

Adults and children following a macrobiotic diet recruited in Boston, MA and Middletown, CT; no further details were provided.

Design

Cross-sectional.

Statistical Analysis

  • Analyses performed:
    • Student's T-test
    • Regression analysis
    • Chi-square analysis
  • Values of urinary MMA and serum vitamin B12 concentrations were log transformed
  • Means of log values were obtained; log value and ranges reported
  • Statistical significance value were not specifically indicated.
Data Collection Summary:

Timing of Measurements

  • Blood samples were drawn from only adults
  • Urine samples were obtained from adults and children
  • Dietary information was obtained from adults and children
  • Weight and height information of the children was obtained when urine was collected
  • Details of the collection methods were not clearly specified.

Dependent Variables

  • Primary variables:
    • Urinary MMA concentration (mmol per mol)
    • Serum vitamin B12 concentration (pmol per L) in adults
  • Secondary variables
    • Dietary vitamin B12 intake score 
      • Determined from reported consumption of 49 food items
      • Calculated by using the average vitamin B12 content of each food item and multiplying that by a coefficient of daily frequency of consumption
      • Products of all food items (except tempeh, miso and sea vegetables) were then summed
    • Length and weight indices based on age- and sex-specific growth curves (percentile) for children. 

Independent Variables

Macrobiotic diet:

  • Duration of this dietary practice
  • Frequency of consumption of certain foods:
    • Eggs
    • Dairy products
    • Seafood
    • Tempeh
    • Miso
    • Sea vegetables.

Control Variables

Dietary variables were controlled for statistically using regression analysis of results.

Note: Vitamin supplements are generally not consumed by this diet group, though this was not measured in this study.

Description of Actual Data Sample:

Initial N

N=153.

  • 110 adults (46 males, 64 females)
  • 42 children 

Attrition (Final N)

N=153.

Age

  • Adults: 21 to 70 years (median  = 33 years)
  • Children: 1.5 to 11.7 years (median =  3.9 years).

Other Relevant Demographics

Dietary information obtained from adults and children:

  • Frequency of consumption was stated as being examined but instrument was not specified
  • Frequency of consumption examined for: 
    • Dairy products
    • Eggs
    • Seafood
    • Various foods common to macrobiotic diet:
      • Tempeh
      • Miso
      • Sea vegetables, categorized according to vitamin B12 content:
        • High (wakame, kombu)
        • Low (hijiki)
        • Unknown (arame, nori, dulse and non-specified)
  • Frequency of consumption for eggs, dairy and seafood categories:
    • Never (zero)
    • Less than one per week (one)
    • More than one per week (two)
  • Frequency of consumption for tempeh, miso and sea vegetables categories:
    • Never (0)
    • One or less per month (one)
    • Two to three per month (two)
    • One per week (three)
    • Two to four per week (four)
    • Five to six per week (five)
    • One per day (six)
    • Four to six per day (seven)
    • More than six per day (eight).

Anthropometrics

  • Weight and height information recorded for children; it was not specified whether this information was self-reported or actually measured
  • Blood samples obtained only from adults
  • Urine samples obtained from adults and children
  • Length of time reported for practicing macrobiotic diet obtained:
    • Adults: One to 379 months (median = 41 months)
    • Children:
      • All children had been fed human milk
      • 30 children (71%) followed macrobiotic diet since weaning
      • Remaining 12 children:
        • Started macrobiotic diet at ages 1.1 to 8.8 years
        • Had consumed macrobiotic diet for eight to 48 months (median = 27 months).

Location

  • Boston, MA
  • Middletown, CT.
Summary of Results:

Key Findings

  • Adults:
    • 51% of adults had low serum vitamin B12 concentration (less than 148pmol per L), with mean serum concentration = 150pmol per L (range 18 to 583pmol per L)
    • 30% of adults had high urinary MMA concentration (4.3mmol per mol creatinine or more). Mean urinary MMA concentration = 4.0mmol per mol (range 1.6 to 20mmol per mol)urinary MMA was inversely correlated with serum vitamin B12 concentration (R=-0.494, P=0.01)
    • significant inverse correlation between serum vitamin B12 concentration and duration of macrobiotic dietary practice (R=-0.210, P=0.03)
  • Children:
    •  MMA concentrations:
      • 55% of children had high urinary MMA concentrations (more than 4.3μmol per mmol creatinine); mean = 4.9mmol per mol (range 0.5 to 35mmol per mol)
      • Urinary MMA concentrations were higher in those children who had consumed a vegetarian diet during their entire lifetime (x = 6.0mmol per mol creatinine, range 0.7 to 35) compared with children who had not (3.0mmol per mol creatinine, 0.5 to 12)
    • Length:
      • 32% of children (11 of 34) for whom length information was obtained were in the 5th or less percentile for length
      • 73% of these children had high MMA concentrations compared with 39% (9 of 23) children whose length measured higher than the 5th percentile (Χ2=3.36, P=0.07)
    • Weight: 15% of children (6 of 41) for whom weight information was obtained were in the 5th or less percentile for weight (Χ2=7.61, P<0.01).

Serum Vitamin B12 and Urinary MMA by Consumption of Major Foods*

  Consumption of Food  
  Never One per Week or Less More than One per Week P** 

Adult serum vitamin B12 (pmol per L)

Dairy 122 (18 to 583) N=57 183 (76 to 485) N= 4 179 (93 to 392) N=12 0.004 
Eggs 139 (18 to 583) N=71 167 (18 to 485) N=25 157 (93 to 358) N=7 0.27
Seafood 111 (18 to 429) N=14 145 (18 to 485) N=45 161 (45 to 583) N=44 0.07
Adult urinary MMA (mmol per mol creatinine)
Dairy 5.3 (2.0 to 20.1) N=15 2.8 (1.6 to 5.3) N=8 2.1 N=1 0.02
Eggs 4.8 (1.6 to 20.1) N=18 3.1 (1.6 to 5.0) N=4 2.2 (2.1 to 2.3) N=2 0.08
Seafood 4.4 (1.6 to 20.1) N=5 5.3 (2.0 to 14.1) N=12 2.6 (1.6 to 5.0) N=7 0.14
Child urinary MMA (mmol per mol creatinine)    
Dairy 7.0 (1.4 to 35.1) N=23 4.4 (0.7 to 18.0) N=11 2.1 (0.5 to 5.1) N=8 0.001
Eggs

6.3 (1.0 to 35.1) N=23

 3.6 (0.5 to 17.1) N=15 3.9 (2.2 to 12.0) N=4 0.10
Seafood

7.3 (2.8 to 12.0) N=7

4.3 (0.7 to 35.1) N=18 4.8 (0.5 to 18.0) N=17 0.50

* Geometric mean (range).

** By regression analyses; similar results were obtained when never vs. ever groups were compared by student's T-test.

Serum vitamin B12 and Uinary MMA by Tertile of Vitamin B12 Intake Score*

  Vitamin B12 Intake Score  
  Low Medium High P**
Serum vitiman B12
Adults (pmol per L)

128 (18 to 508) N=30

139 (18 to 583) N=28

184 (45 to 399) N=28

0.03
Adults' intake score 0

0.01 to 0.15

0.16 to 1.7

 
Urinary MMA

Children (mmol per mol creatinine)

6.7 (1.4 to 35.1) N=13

5.9 (1.7 to 25) n=12

2.6 (0.5 to 10) N=12

0.005

Children's intake score

0-0.02

0.02-0.19

0.20 to 0.77  

* Geometric mean (range).

** By regression analyses; similar results were obtained when never vs. ever groups were compared by student's T-test.

Other Findings

  • Adults:
    • Vitamin B12 concentration was not correlated with age (R=-0.091, P=0.3) and did not differ by sex 
    • Mean serum vitamin B12 concentrations tended to be lower and mean MMA concentrations tended to be higher for adults who consumed no dairy, eggs or seafood; this was statistically significant only for dairy (P<0.05)
  • Children:
    • Urinary MMA was not related to child's age (R=-0.252, P=0.11)
    • Mean MMA concentrations tended to be higher for children who consumed no dairy, eggs or seafood
    • Statistically significant only for dairy (P<0.05)
    • 70% of children not consuming dairy had high urinary MMA compared to 37% who consumed dairy (chi-square test, P=0.03)
    • Urinary MMA was higher with lower tertile of vitamin B12 intake
  • For both Adults and Children: Urinary MMA concentration was not correlated with consumption of tempeh, miso or sea vegetables.
Author Conclusion:

Individuals consuming a vegetarian diet for long periods of time may be at risk of vitamin B12 deficiency.

Funding Source:
Not-for-profit
Cincinnati Children’s Hospital Research Founation, Kushi Institute, East-West Foundation
Reviewer Comments:
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) 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? 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
  2.3. Were health, demographics, and other characteristics of subjects described? ???
  2.4. Were the subjects/patients a representative sample of the relevant population? No
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? 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? No
  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
  4.3. 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? No
  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? No
  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? No
  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
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? Yes
  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
  6.6. 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
  6.8. 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? ???
  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? ???
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.2. Was the study free from apparent conflict of interest? No