EAL

NSUP: Vitamin B12 (2008)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To determine the relationship between vitamin B₁₂ intake and the current variables used to evaluate vitamin B₁₂ status in 98 post-menopausal women.

Inclusion Criteria:

One year or more post-menopausal
75 years or older
Completed diet records
Not currently receiving intramuscular vitamin B₁₂ treatments.

Exclusion Criteria:

Drug or alcohol addiction
Malignant disease
Current steroid treatment
Osteomalacia
Diabetes
Unstable thyroid disease
Chronic inflammatory diseases
Active liver or kidney disease.

Description of Study Protocol:

Recruitment: Telephone
Design: Cross-sectional. They recorded the vitamin B₁₂ intake for 98 post-menopausal women and related the intake to markers of vitamin B₁₂deficiency.
Blinding used: N/A.

Intervention

Dietary intakes of vitamin B₁₂ were determined from a seven-day weighed-food record. 5 of the subjects (54%) took vitamin supplements regularly, usually as multi-vitamin preparations. The supplements contained a median amount of one mcg vitamin B₁₂ (range: one mcg to 18mcg). 34 of the subjects who used supplements (64%) were taking oral multi-vitamin supplements containing one mcg vitamin B₁₂. Subjects were divided into dietary intake quintiles for analysis.

Statistical Analysis

Mann-Whitney U-test
Kruskal-Wallis test
Spearman correlation coefficient.

Data Collection Summary:

Timing of Measurements

The following measurements were taken at one visit:

Individual information on health, medical, reproductive and menopausal history and lifestyle
Seven-day weighed food records were obtained at baseline after the subjects were provided thorough oral and written instructions and were shown how to use the supplied electronic scale (limit of 2,000g; Soehnle Domino, Murrhardt, Germany)
Gastric pH
Alkali-challenge test.

Dependent Variables

Serum cobalamin
Transcobalamin (TC) saturated with vitamin B₁₂(holo-TC)
TC saturation (holo-TC/total TC)
Methylmalonic acid (MMA)
Total homocysteine (tHcy).

Independent Variables

Vitamin B₁₂ intake from diet only
Vitamin B₁₂for supplement users.

Description of Actual Data Sample:

Initial N: 98 females
45 of the subjects (46%) did not use vitamin B₁₂ supplements
The dietary intakes of vitamin B₁₂for the supplement users (N=53) and non-users (N=45)
Attrition: N/A
Age: 57 (53 to 64) years
Ethnicity: Not described
Anthropometrics: BMI=23.1 (21 to 25.8).

Location

Department of Clinical Biochemistry, Nørrebrogade Section, Aarhus Hospital (MVB and EN), the Department of Clinical Biochemistry, Aalborg Hospital (MVB)
Department of Clinical Biochemistry, Skejby Hospital (JM), the University Hospital of Aarhus, Aarhus, Denmark
Institute for Optimum Nutrition, Copenhagen, Denmark.

Summary of Results:

Vitamin B₁₂-related variables, except gastric pH, correlate significantly with total vitamin B₁₂ intake. Reflecting a daily dose of six micrograms vitamin B₁₂ ensures a steady concentration of serum cobalamin, holo-TC, and the metabolic markers tHcy and MMA.
Subjects taking supplements (54%) had higher circulating concentrations of cobalamin and TC saturation and lower concentrations of MMA and tHcy than did those not taking supplements.

Author Conclusion:

This study showed that vitamin B₁₂status, as judged by available laboratory tests, was associated with vitamin B₁₂ intake in this population and that the use of supplements appears to protect against concentrations of vitamin B₁₂-related variables in the deficiency range
A daily vitamin B₁₂ intake of six micrograms appears to be sufficient to normalize all of the vitamin B₁₂-related variables, which suggests that this dose might be more adequate for the general adult population than the current RDA of 2.4 micrograms.

Funding Source:

Government:

EU Biomed, Danish Ministry of Health,

Not-for-profit

Foundation associated with industry:

Reviewer Comments:

Small subject size
Limited presentation of demographic data
No power calculation presented.

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?		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
	2.3.	Were health, demographics, and other characteristics of subjects described?	Yes
	2.4.	Were the subjects/patients a representative sample of the relevant population?	Yes
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?	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
4.	Was method of handling withdrawals described?		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
	4.3.	Were all enrolled subjects/patients (in the original sample) accounted for?	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
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
	5.2.	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.)	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
	5.5.	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?		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?	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
	6.5.	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?	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
	8.1.	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)?	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
	8.7.	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?		Yes
	10.1.	Were sources of funding and investigators' affiliations described?	Yes
	10.2.	Was the study free from apparent conflict of interest?	Yes