A systematic review of the vitamin B12, folate and homocysteine triad across body mass index
Bibliographic record
Abstract
Summary Objective Multiple studies have explored the association between serum or plasma vitamin B12 status and obesity, in part because of the relationship between elevated homocysteine concentrations and atherosclerosis. This review will address the inconsistent finding of these studies with the objective of determining whether vitamin B12 concentrations are lower in people with higher body mass indices. Design MEDLINE and EMBASE were searched to February 2017. Observational studies in general and clinical populations comparing serum/plasma B12 concentrations across groups of different body mass indices were selected. We did network and pairwise meta‐analyses of serum/plasma B12, folate and homocysteine using frequentist techniques. Evidence‐based items potentially indicating risk of bias were assessed. Results Of 844 citations, we identified 19 eligible observational studies with 7,055 participants. The overall network, while showing no significant inconsistency between indirect and direct comparisons ( P = 0.34), was qualitatively inconsistent. Based on the results of the meta‐regression, in an exploratory sub‐network meta‐analysis where obesity groups were combined, we excluded disease‐specific populations and studies with inadequate description of populations. The direction of the indirect and direct evidence was consistent. The pairwise results from this sub‐network showed lower levels of B12 in people with higher body mass indices: obesity versus control difference in means (MD) −56 pmol L −1 (95% CI −90, −23), obesity versus overweight MD −21 pmol L −1 (95% CI −37, −5) and overweight versus control MD −51 pmol L −1 (95% CI −51, −24). Heterogeneity remained very large for most comparisons, and all the studies carried a high risk for bias. Conclusions This review did not establish an inverse association (or J‐curve) between serum or plasma B12 concentrations and body mass index, but the direct pairwise evidence is consistent with an inverse association and supports further investigation.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.007 | 0.003 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.011 | 0.002 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".