A comprehensive review and meta-regression analysis of randomized controlled trials examining the impact of vitamin B12 supplementation on homocysteine levels

CONTEXT

Although some research suggests that vitamin B12 (hereafter, B12) supplements can lower homocysteine (Hcy) levels and treat hyperhomocysteinemia, these results are still ambiguous when B12 is taken as an isolated supplement.

OBJECTIVE

This study sought to determine how existing randomized controlled trials (RCTs) could be used to examine the effects of B12 supplementation on Hcy.

DATA SOURCES

To find pertinent RCTs up to June 2022, databases, including PubMed/Medline, Web of Science, Scopus, Cochrane Library, and Embase, were searched.

DATA EXTRACTION

All selected RCTs investigated the impact of B12 supplements on Hcy. A meta-analysis of the eligible studies was performed using the random-effects model.

DATA ANALYSIS

This review included a total of 21 RCTs (N = 1625 participants). Hcy levels were significantly lower after B12 supplementation compared with the control group (pooled weighted mean difference, -4.15 μmol/L; 95% confidence interval, -4.86, -3.45; P < 0.001), and this reduction was even greater with intervention durations ≥12 weeks and doses >500 µg/d. Furthermore, the effect of B12 supplementation in the form of hydroxocobalamin on the reduction of Hcy level was greater compared with other forms.

CONCLUSION

In conclusion, this meta-analysis shows that B12 supplementation has a positive impact on lowering blood Hcy levels, particularly when administered for a longer period and at a larger dose.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration no. CRD42022364066.

Perspective: Practical Approach to Preventing Subclinical B12 Deficiency in Elderly Population

Vitamin B12 (also known as cobalamin) is an essential water-soluble vitamin that plays a pivotal role for several physiologic functions during one's lifespan. Only certain microorganisms are able to synthetize B12, thus humans obtain cobalamin exclusively from their diet, specifically from animal-derived foods. Specific sub-group populations are at risk of vitamin B12 subclinical deficiency due to different factors including poor intake of animal source foods and age-dependent decrease in the capacity of intestinal B12 uptake. Consumption of animal products produces some negative health issues and negatively impacts sustainability while a plant-based diet increases the risk of B12 deficiency. Taking a cue from the aforementioned considerations, this narrative review aims to summarize facts about B12 deficiency and the burden of inadequate dietary intake in elderly population, as well as to discuss sustainable approaches to vitamin B12 deficiency in aging population.

Vitamin B12-fortified toothpaste improves vitamin status in elderly people: a randomized, double-blind, placebo-controlled study

BACKGROUND

Elderly people are at risk for vitamin B12 deficiency.

AIMS

We studied the ability of vitamin B12-enriched toothpaste vs. placebo to increase vitamin B12 status in elderly subjects.

METHODS

We conducted a randomized double-blind placebo-controlled intervention in 103 elderly subjects. Serum concentrations of vitamin B12, holotranscobalamin (holoTC), methylmalonic acid (MMA), and plasma total homocysteine (tHcy) were measured at baseline and after 3 months.

RESULTS

92 subjects met the inclusion criteria, completed the 3 months study, and were included in the data analysis. After the intervention, concentrations of vitamin B12 were higher [mean (SD) = 368 (123) vs. 295 (123) pmol/L; p = 0.005] and holoTC tended to be higher [112 (48) vs. 91 (68) pmol/L; p = 0.088] in the vitamin B12 group compared with the placebo group. The changes of serum vitamin B12 [54 (74) vs. 3 (60) pmol/L, p < 0.001], holoTC [21 (34) vs. 2 (32) pmol/L, p = 0.007], and tHcy [- 0.9 (2.3) vs. 0.3 (1.9) µmol/L, p = 0.010] were significantly different between the intervention groups. Mean percentage increase of serum vitamin B12 (+ 23% corresponds to + 54 pmol/L) in the vitamin B12 toothpaste group suggests that the intervention had provided an additional daily intake of approximately + 7 µg oral B12. Common diseases and drugs did not predict the change of blood markers in the vitamin group. No side effects were observed.

CONCLUSIONS

The toothpaste enriched with 100 µg cyanocobalamin/g has increased vitamin B12 status and can thus be used for preventing vitamin B12 depletion in elderly people. The trial was registered at ClinicalTrials.gov: NCT02679833.

Effect of two different sublingual dosages of vitamin B12 on cobalamin nutritional status in vegans and vegetarians with a marginal deficiency: A randomized controlled trial

BACKGROUND & AIMS

Vegetarians and vegans are more vulnerable to vitamin B₁₂ deficiency with severe risks of megaloblastic anemia, cognitive decline, neuropathy, and depression. An easy and simple method of supplementation consists of taking one weekly dosage of 2000 μg. However, single large oral doses of vitamin B₁₂ are poorly absorbed. The present research evaluates the ability of two different sublingual dosages of vitamin B₁₂ (350 μg/week vs 2000 μg/week) in improving cyanocobalamin (vitamin B₁₂) nutritional status in vegans and vegetarians with a marginal deficiency.

METHODS

A 12-week randomized, double-blind, controlled, parallel intervention trial was performed. Forty subjects with marginal vitamin B₁₂ deficiency were enrolled and randomly divided into two groups: test group Ld (low dose, 350 μg/week) and control group Hd (high dose, 2000 μg/week) vitamin B₁₂ supplementation. Blood samples were collected at baseline and after 15, 30, 60, and 90 days from the intervention for the determination of vitamin B₁₂, related metabolic markers, and blood cell counts.

RESULTS

Two-way analysis of variance showed a significant effect of time (P < 0.0001) and of time × treatment interaction (P = 0.012) on serum concentration of vitamin B₁₂ that increased after 90-day supplementation (Ld and Hd) compared to baseline. Both the supplements increased (P < 0.0001, time effect) the levels of holotranscobalamin, succinic acid, methionine and wellness parameter, while decreased (P < 0.0001, time effect) the levels of methylmalonic acid, homocysteine and folate compared to baseline. No difference was observed between groups (Ld vs Hd). No effect was detected for vitamin B₆ and blood cell count.

CONCLUSIONS

In our experimental conditions, both supplements were able to restore adequate serum concentrations of vitamin B₁₂ and to improve the levels of related metabolic blood markers in subjects with a marginal deficiency. The results support the use of a sublingual dosage of 50 μg/day (350 μg/week) of cobalamin, instead of 2000 μg/week (provided as a single dose), to reach a state of nutritional adequacy of vitamin B₁₂ in this target population. This study was registered at www.isrctn.org as ISRCTN75099618.

Vitamin B12 deficiency

Vitamin B₁₂ (B12; also known as cobalamin) is a B vitamin that has an important role in cellular metabolism, especially in DNA synthesis, methylation and mitochondrial metabolism. Clinical B12 deficiency with classic haematological and neurological manifestations is relatively uncommon. However, subclinical deficiency affects between 2.5% and 26% of the general population depending on the definition used, although the clinical relevance is unclear. B12 deficiency can affect individuals at all ages, but most particularly elderly individuals. Infants, children, adolescents and women of reproductive age are also at high risk of deficiency in populations where dietary intake of B12-containing animal-derived foods is restricted. Deficiency is caused by either inadequate intake, inadequate bioavailability or malabsorption. Disruption of B12 transport in the blood, or impaired cellular uptake or metabolism causes an intracellular deficiency. Diagnostic biomarkers for B12 status include decreased levels of circulating total B12 and transcobalamin-bound B12, and abnormally increased levels of homocysteine and methylmalonic acid. However, the exact cut-offs to classify clinical and subclinical deficiency remain debated. Management depends on B12 supplementation, either via high-dose oral routes or via parenteral administration. This Primer describes the current knowledge surrounding B12 deficiency, and highlights improvements in diagnostic methods as well as shifting concepts about the prevalence, causes and manifestations of B12 deficiency.

Novel vitamin B12-producing Enterococcus spp. and preliminary in vitro evaluation of probiotic potentials

Vitamin B₁₂ is an essential nutrient required for crucial metabolic processes in humans. Vitamin B₁₂-producing lactic acid bacteria (LAB) have been attracting increased attentions currently because of the generally recognized as safe (GRAS) status. Most of recent studies focused on Lactobacillus, and little is known about B₁₂-producing Enterococcus. In the present study, five Enterococcus strains isolated from infant feces were identified as vitamin B₁₂ producers. Among them, Enterococcus faecium LZ86 had the highest B₁₂ production (499.8 ± 83.7 μg/L), and the B₁₂ compound from LZ86 was identified as the biological active adenosylcobalamin, using reversed phase high-performance liquid (RP-HPLC) chromatogram. We examined basic probiotic and safety properties of E. faecium LZ86 and found that it was able to survive harsh environmental conditions (hot temperature, cold temperature, ethanol and osmotic stresses), tolerate gastric acid (pH 2.0, 3 h) and bile salts (0.3%), and adhere to Caco-2 cells. We also showed that E. faecium LZ86 is devoid of transferable antibiotic resistance and potential virulence factors. Together, here we report a B₁₂-producing E. faecium strain LZ86 firstly, which has desirable probiotic properties and may serve as a good candidate for vitamin B₁₂ fortification in food industry.

Effect of administration route on the pharmacokinetics of cobalamin in elderly patients: a randomized controlled trial

BACKGROUND

The gold standard for cobalamin deficiency treatment is administration of cobalamin by intramuscular injection. The injection is painful and inconvenient, particularly for elderly persons. Cobalamin might also be administered intranasally. Previous studies do not provide insight into the pharmacokinetics of intranasal cobalamin administration in comparison with cobalamin injection.

AIM

To quantify the pharmacokinetics of intranasally and intramuscularly administered cobalamin to determine if intranasal administration might be an alternative for intramuscular administration.

METHODS

Ten inpatients and outpatients of a geriatrics unit were recruited and randomly assigned to receive a single dose of 1000 μg cobalamin administered either by intranasal spray or intramuscular injection (5 per group). Inclusion criteria were written informed consent, age >65 years, and a cobalamin serum concentration <200 pmol/L. Total cobalamin serum concentrations were determined 10 times within 48 hours after administration. The differences in Cmax, Tmax, and AUC0-48 h per administration route were statistically compared using ANOVA.

RESULTS

The average Cmax was 1 nmol/L after intranasal and 38.5 nmol/L after intramuscular administration. The average Tmax for intranasal and intramuscular administration was 42 minutes versus 342 minutes, respectively, and the AUC0-48 h was 1.3 µmol/L/min versus 45.4 µmol/L/min, respectively. These values also differed significantly (P<0.05). The estimated bioavailability of the intranasal administration was 2%.

CONCLUSIONS

The pharmacokinetics of intranasal and intramuscular cobalamin administration in elderly, cobalamin-deficient patients differ significantly. However, the estimated 2% bioavailability of cobalamin after intranasal administration makes intranasal cobalamin administration a potentially interesting administration route for elderly patients. Netherlands Trial Registry identifier: NTR 3005.

Biologically active vitamin B12 compounds in foods for preventing deficiency among vegetarians and elderly subjects

The usual dietary sources of vitamin B12 are animal-source based foods, including meat, milk, eggs, fish, and shellfish, although a few plant-based foods such as certain types of dried lavers (nori) and mushrooms contain substantial and considerable amounts of vitamin B12, respectively. Unexpectedly, detailed characterization of vitamin B12 compounds in foods reveals the presence of various corrinoids that are inactive in humans. The majority of edible blue-green algae (cyanobacteria) and certain edible shellfish predominately contain an inactive corrinoid known as pseudovitamin B12. Various factors affect the bioactivity of vitamin B12 in foods. For example, vitamin B12 is partially degraded and loses its biological activity during cooking and storage of foods. The intrinsic factor-mediated gastrointestinal absorption system in humans has evolved to selectively absorb active vitamin B12 from naturally occurring vitamin B12 compounds, including its degradation products and inactive corrinoids that are present in daily meal foods. The objective of this review is to present up-to-date information on various factors that can affect the bioactivity of vitamin B12 in foods. To prevent vitamin B12 deficiency in high-risk populations such as vegetarians and elderly subjects, it is necessary to identify plant-source foods that contain high levels of bioactive vitamin B12 and, in conjunction, to prepare the use of crystalline vitamin B12-fortified foods.

A vitamin B-12 supplement of 500 μg/d for eight weeks does not normalize urinary methylmalonic acid or other biomarkers of vitamin B-12 status in elderly people with moderately poor vitamin B-12 status

Plasma vitamin B-12 is the most commonly used biomarker of vitamin B-12 status, but the predictive value for low vitamin B-12 status is poor. The urinary methylmalonic acid (uMMA) concentration has potential as a functional biomarker of vitamin B-12 status, but the response to supplemental vitamin B-12 is uncertain. A study was conducted to investigate the responsiveness of uMMA to supplemental vitamin B-12 in comparison with other biomarkers of vitamin B-12 status [plasma vitamin B-12, serum holotranscobalamin (holoTC), plasma MMA] in elderly people with moderately poor vitamin B-12 status. A double-blind, placebo-controlled, randomized 8-wk intervention study was carried out using vitamin B-12 supplements (500 μg/d, 100 μg/d, and 10 μg/d cyanocobalamin) in 100 elderly people with a combined plasma vitamin B-12 <250 pmol/L and uMMA ratio (μmol MMA/mmol creatinine) >1.5. All biomarkers had a dose response to supplemental vitamin B-12. Improvements in plasma vitamin B-12 and serum holoTC were achieved at cobalamin supplements of 10 μg/d, but even 500 μg/d for 8 wk did not normalize plasma vitamin B-12 in 8% and serum holoTC in 12% of people. The response in uMMA was comparable with plasma MMA; 15-25% of people still showed evidence of metabolic deficiency after 500 μg/d cobalamin for 8 wk. There was a differential response in urinary and plasma MMA according to smoking behavior; the response was enhanced in ex-smokers compared with never-smokers. uMMA offers an alternative marker of metabolic vitamin-B12 status, obviating the need for blood sampling.

Systematic review with dose-response meta-analyses between vitamin B-12 intake and European Micronutrient Recommendations Aligned's prioritized biomarkers of vitamin B-12 including randomized controlled trials and observational studies in adults and elderly persons

BACKGROUND

Many randomized controlled trials (RCTs) and observational studies have provided information on the association between vitamin B-12 intake and biomarkers. The use of these data to estimate dose-response relations provides a useful means to summarize the body of evidence.

OBJECTIVE

We systematically reviewed studies that investigated vitamin B-12 intake and biomarkers of vitamin B-12 status and estimated dose-response relations with the use of a meta-analysis.

DESIGN

This systematic review included all RCTs, prospective cohort studies, nested case-control studies, and cross-sectional studies in healthy adult populations published through January 2010 that supplied or measured dietary vitamin B-12 intake and measured vitamin B-12 status as serum or plasma vitamin B-12, methylmalonic acid (MMA), or holotranscobalamin. We calculated an intake-status regression coefficient ( ) for each individual study and calculated the overall pooled and SE ( ) by using random-effects meta-analysis on a double-log scale.

RESULTS

The meta-analysis of observational studies showed a weaker slope of dose-response relations than the meta-analysis of RCTs. The pooled dose-response relation of all studies between vitamin B-12 intake and status indicated that a doubling of the vitamin B-12 intake increased vitamin B-12 concentrations by 11% (95% CI: 9.4%, 12.5%). This increase was larger for studies in elderly persons (13%) than in studies in adults (8%). The dose-response relation between vitamin B-12 intake and MMA concentrations indicated a decrease in MMA of 7% (95% CI: -10%, -4%) for every doubling of the vitamin B-12 intake. The assessment of risk of bias within individual studies and across studies indicated risk that was unlikely to seriously alter these results.

CONCLUSION

The obtained dose-response estimate between vitamin B-12 intake and status provides complementary evidence to underpin recommendations for a vitamin B-12 intake of populations.

Oral vitamin B12 for patients suspected of subtle cobalamin deficiency: a multicentre pragmatic randomised controlled trial

Background

Evidence regarding the effectiveness of oral vitamin B12 in patients with serum vitamin B12 levels between 125-200 pM/l is lacking. We compared the effectiveness of one-month oral vitamin B12 supplementation in patients with a subtle vitamin B12 deficiency to that of a placebo.

Methods

This multicentre (13 general practices, two nursing homes, and one primary care center in western Switzerland), parallel, randomised, controlled, closed-label, observer-blind trial included 50 patients with serum vitamin B12 levels between 125-200 pM/l who were randomized to receive either oral vitamin B12 (1000 μg daily, N = 26) or placebo (N = 24) for four weeks. The institution's pharmacist used simple randomisation to generate a table and allocate treatments. The primary outcome was the change in serum methylmalonic acid (MMA) levels after one month of treatment. Secondary outcomes were changes in total homocysteine and serum vitamin B12 levels. Blood samples were centralised for analysis and adherence to treatment was verified by an electronic device (MEMS; Aardex Europe, Switzerland). Trial registration: ISRCTN 22063938.

Results

Baseline characteristics and adherence to treatment were similar in both groups. After one month, one patient in the placebo group was lost to follow-up. Data were evaluated by intention-to-treat analysis. One month of vitamin B12 treatment (N = 26) lowered serum MMA levels by 0.13 μmol/l (95%CI 0.06-0.19) more than the change observed in the placebo group (N = 23). The number of patients needed to treat to detect a metabolic response in MMA after one month was 2.6 (95% CI 1.7-6.4). A significant change was observed for the B12 serum level, but not for the homocysteine level, hematocrit, or mean corpuscular volume. After three months without active treatment (at four months), significant differences in MMA levels were no longer detected.

Conclusions

Oral vitamin B12 treatment normalised the metabolic markers of vitamin B12 deficiency. However, a one-month daily treatment with1000 μg oral vitamin B12 was not sufficient to normalise the deficiency markers for four months, and treatment had no effect on haematological signs of B12 deficiency.

Effect of physiological doses of oral vitamin B12 on plasma homocysteine: a randomized, placebo-controlled, double-blind trial in India

BACKGROUND/OBJECTIVES

Vitamin B(12) (B(12)) deficiency is common in Indians and a major contributor to hyperhomocysteinemia, which may influence fetal growth, risk of type II diabetes and cardiovascular disease. The purpose of this paper was to study the effect of physiological doses of B(12) and folic acid on plasma total homocysteine (tHcy) concentration.

SUBJECTS/METHODS

A cluster randomized, placebo-controlled, double-blind, 2 x 3 factorial trial, using the family as the randomization unit. B(12) was given as 2 or 10 microg capsules, with or without 200 microg folic acid, forming six groups (B(0)F(0), B(2)F(0), B(10)F(0), B(0)F(200), B(2)F(200) and B(10)F(200)). Plasma tHcy concentration was measured before and after 4 and 12 months of supplementation.

RESULTS

From 119 families in the Pune Maternal Nutrition Study, 300 individuals were randomized. There was no interaction between B(12) and folic acid (P=0.14) in relation to tHcy concentration change and their effects were analyzed separately: B(0) vs. B(2) vs. B(10); and F(0) vs. F(200). At 12 months, tHcy concentration reduced by a mean 5.9 (95% CI: -7.8, -4.1) micromol/l in B(2), and by 7.1 (95% CI: -8.9, -5.4) micromol/l in B(10), compared to nonsignificant rise of 1.2 (95% CI: -0.5, 2.9) micromol/l in B(0). B(2) and B(10) did not differ significantly. In F(200), tHcy concentration decreased by 4.8 (95% CI: -6.3, -3.3) micromol/l compared to 2.8 (95% CI: -4.3, -1.2) micromol/l in F(0).

CONCLUSION

Daily oral supplementation with physiological doses of B(12) is an effective community intervention to reduce tHcy. Folic acid (200 microg per day) showed no additional benefit, neither had any unfavorable effects.

Studies of biomarker responses to intervention with vitamin B-12: a systematic review of randomized controlled trials

BACKGROUND

Mild vitamin B-12 deficiency is common among older adults, but evidence for setting dietary recommendations is limited because most studies have administered vitamin B-12 via nonoral routes or at doses several hundred times higher than current recommendations. Furthermore, different biomarkers of vitamin B-12 status have not been systematically reviewed.

OBJECTIVE

The aim was to assess the effectiveness of biomarkers of vitamin B-12 status through a systematic review of published randomized controlled trials of oral vitamin B-12 supplementation.

DESIGN

Methods included a structured search strategy on Ovid MEDLINE, EMBASE (Ovid), and Cochrane databases; formal inclusion and exclusion criteria; data extraction; validity assessment; and meta-analysis.

RESULTS

Eight randomized controlled trials were included, and all studies measured serum and plasma total vitamin B-12, 3 studies measured methylmalonic acid, and 6 studies measured total homocysteine response. All 3 biomarkers were found to be effective measures of altered vitamin B-12 intake in populations with low and borderline baseline vitamin B-12 status (P < 0.00001); however, in the case of total vitamin B-12, substantial heterogeneity that could not be fully explained by subgroup analysis was observed. Insufficient data were available to determine the effectiveness of plasma holotranscobalamin, which was measured in only one randomized controlled trial.

CONCLUSIONS

The available evidence suggests that plasma and serum concentrations of total vitamin B-12, methylmalonic acid, and total homocysteine are all effective biomarkers of a change in vitamin B-12 intake; however, because the available data were limited, it was not possible to examine fully the factors that could explain the substantial heterogeneity in total vitamin B-12. Future trials should include low-dose vitamin B-12 in adults across the entire age spectrum and measure the holotranscobalamin response to supplementation.

A reappraisal of the impact of dairy foods and milk fat on cardiovascular disease risk

Background

This review provides a reappraisal of the potential effects of dairy foods, including dairy fats, on cardiovascular disease (CVD)/coronary heart disease (CHD) risk. Commodities and foods containing saturated fats are of particular focus as current public dietary recommendations are directed toward reducing the intake of saturated fats as a means to improve the overall health of the population. A conference of scientists from different perspectives of dietary fat and health was convened in order to consider the scientific basis for these recommendations.

Aims

This review and summary of the conference focus on four key areas related to the biology of dairy foods and fats and their potential impact on human health: (a) the effect of dairy foods on CVD in prospective cohort studies; (b) the impact of dairy fat on plasma lipid risk factors for CVD; (c) the effects of dairy fat on non-lipid risk factors for CVD; and (d) the role of dairy products as essential contributors of micronutrients in reference food patterns for the elderly.

Conclusions

Despite the contribution of dairy products to the saturated fatty acid composition of the diet, and given the diversity of dairy foods of widely differing composition, there is no clear evidence that dairy food consumption is consistently associated with a higher risk of CVD. Thus, recommendations to reduce dairy food consumption irrespective of the nature of the dairy product should be made with caution.

A novel solution is needed to correct low nutrient intakes in elderly long-term care residents

Currently, there is no consensus about how to best treat malnutrition in elderly long-term care residents. A recent study found that the traditional treatment method of serving small, frequent meals was not effective at increasing energy intake. This review describes strategies to treat malnutrition in this vulnerable population.