VN: Vitamin B-12 (2011)

Study Design:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:

To investigate some haematological aspects resulting from different degrees of animal-food deprivation.

Inclusion Criteria:

Attendees at either of these events:

  • German Federation of Vegetarians conference
  • Vegan Society of the Netherlands summer camp.

No other inclusion criteria specified.

Exclusion Criteria:

Existing acute or chronic disease.

Description of Study Protocol:


Volunteers recruited from participants at a conference of the German Federation of Vegetarians or at a summer camp of the Vegan Society of the Netherlands. Other than this description, no further details were provided.



Subjects stratified into three groups depending on self-reported habitual dietary pattern:

  • Vegan
  • Lacto- or lacto-ovo-vegetarian
  • Semi-vegetarian (meat intake once weekly).

Blinding used

Not applicable.


Not applicable.

Statistical Analysis

 Analyses performed using SPSS v.9.0:

  • Two-tailed Mann-Whitney test used for inter-group comparisons
  • Backward regression analyses applied. Log transformed data used for skewed parameters.

Results reported as median (10th/90th percentile) for:

  • Biochemical and haematological parameters of participants
  • Influence of vitamin B12 deficiency on certain haematological markers.

Results reported as mean (95th confidence level) for platelet count according to quartiles for concentrations of homocysteine and methylmalonic acid.

Statistical significance=P<0.05.

Data Collection Summary:

Timing of Measurements

Single blood sample collected after a 12-hour fast

Dependent Variables

  • Primary variables
    • Serum concentrations of:
      • Methylmalonic acid (MMA) (nmol/L)
      • Homocysteine (HCY) (μmol/L)
      • Mean corpuscular volume (MCV) (fL)
      • Platelet count (x109/L).
  • Secondary variables
    • Serum concentrations of:
      • Iron (μg/dL)
      • Vitamin B12 (pmol/L)
      • Folate (nmol/L)
      • Ferritin (μg/L)
      • Transferrin (g/L)
      • Transferrin saturation (%).

Independent Variables

Type of dietary pattern (vegan, lacto-, lacto-ovo- or semi-vegetarian).

Control Variables

Not applicable.

Description of Actual Data Sample:

Initial N

n=113 (49 males, 64 females)

  • 29 vegans
  • 64 lacto- and lacto-ovo-vegetarians
  • 20 semi-vegetarians.

Attrition (final N)



46±15 years.


Not reported.

Other relevant demographics

No further information was provided.


No anthropometric measurements were reported.


Germany and The Netherlands.

Summary of Results:

Key Findings

Vitamin B12 status was compromised by the degree of animal food restriction.

Median (10th, 90th percentiles):


Serum B12 (pmol/L): 218 (158-302)

MMA (nmol/L): 206 (147-649)

Lacto-ovo and lacto-vegetarians

Serum B12 (pmol/L): 192 (135-358)

MMA (nmol/L): 355 (154-1535)*


Serum B12 (pmol/L): 148 (112-290)*#

MMA (nmol/L): 708 (243-3024)*#

*Significantly different from semi-vegetarians

#Significantly different from lacto-ovo and lacto-vegetarians

Compared with the other groups, vegans had:

  • Highest median MMA concentration

  • Lowest median serum vitamin B12 concentration

  • Highest median HCY concentration

Compared with the lacto- and lacto-ovo groups, vegans had:

  • Higher MCV

  • Lower lymphocyte count.

Abnormal values for the following metabolic and haematological markers were found in the study population:

Prevalence of Abnormal Values

Metabolic or haematological marker

Cutoff level

% of study population








<30μg/L, males

<15μg/L, females


Transferrin saturation






Platelet count



Mean platelet volume



**In text of article it said 85%, but in chart it was diagrammed as 58%.


Other Findings

Compared with those subjects who had normal MMA and HCY levels, subjects with elevated MMA and HCY had:

  • Been following a vegetarian diet for a longer time 

  • Lower lymphocyte count 

  • Lower platelet count

  • Higher MCV.



Normal MMA and Normal HCY

Elevated MMA and Normal HCY

Elevated MMA and Elevated HCY



Number (%)



 35 (31)



Age (y)









Time on diet (y)









Serum vitamin B12 (pmol/L)









MMA (nmol/L)









HCY (μmol/L)









Folate (nmol/L)









Creatinine (μmol/L) 









Lymphocyte count (x109/L)









MCV (fL)









Platelet count (x109/L)









a to Elevated MMA/Normal HCY group

b to Elevated MMA/Elevated HCY group

Mean MCV was significantly higher in vitamin B12-deficient subjects versus non-deficient subjects only within the upper range of transferrin saturation (P=0.003).

Author Conclusion:

Vitamin B12 and iron status are compromised by a vegetarian diet. Beneficial effects expected from a vegetarian diet should be evaluated in light of the potential harm that may occur as a result of iron and vitamin B12 deficiencies.

Funding Source:
University/Hospital: University Hospital of Saarland, Homburg, Germany
Other: Not reported
Reviewer Comments:
  • No information on specifics of dietary patterns. No diet records or food frequency questionnaires.
  • No comment on whether subjects ingested dietary supplements.
  • Discrepancy of data: as noted in table, text said 85% and chart said 58% of subjects had abnormal MMA levels.
  • Study may not have high generalizability.
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) 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
  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? No
  2.4. Were the subjects/patients a representative sample of the relevant population? ???
3. Were study groups comparable? No
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) No
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? ???
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) ???
  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.) ???
  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? 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? 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? 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? No
  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)? No
  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? N/A
10. Is bias due to study's funding or sponsorship unlikely? Yes
  10.1. Were sources of funding and investigators' affiliations described? No
  10.2. Was the study free from apparent conflict of interest? Yes