Methylmalonic acid, vitamin B12, and mortality risk in patients with preexisting coronary heart disease: a prospective cohort study.

BACKGROUND: The inconsistent relationship between Vitamin B12 (B12), methylmalonic acid (MMA, marker of B12 deficiency) and mortality was poorly understood, especially in patients with coronary heart disease (CHD). This study aims to investigate the association of serum MMA, and B12-related biomarkers (serum level, dietary intake, supplement use, and sensibility to B12) with all-cause and cardiovascular mortality in adults with CHD. METHODS: The data of this study were from a subcohort within the US National Health and Nutrition Examination Survey (NHANES). We included adults with preexisting CHD with serum MMA and B12, and dietary B12 intake measurements at recruitment. All participants were followed up until 31 December 2019. Weighted Cox proportional hazard regression was used to estimate hazard ratios (HR) and 95% CI of mortality risk. RESULTS: Overall, 1755 individuals (weighted mean [SE] age, 65.2 [0.5] years; 1047 men [weighted 58.5%]) with CHD were included, with geometric mean levels of serum MMA 182.4 nmol/L, serum B12 494.5 pg/ml, and dietary B12 intake 4.42 mg/day, and percentage of B12 supplements use 39.1%. During a median follow-up of 7.92 years, 980 patients died. Serum B12 concentration, dietary B12 intake and supplements use were not significantly associated with mortality risk (each p ≥ 0.388). In contrast, individuals in the top tertile of MMA had multivariable-adjusted HRs (95% CIs) of 1.70 (1.31-2.20) for all-cause mortality, and 2.00 (1.39-2.89) for cardiovascular mortality (both p trend < 0.001) compared to those in the bottom tertile of MMA. MMA-related mortality risk was particularly higher among participants with sufficient serum B12 (p < 0.001). CHD patients with increased levels of both MMA and B12 had a doubled mortality risk compared to those with lower MMA and B12 (p < 0.001). CONCLUSION: MMA accumulation but not serum or dietary vitamin B12 was associated with increased cardiovascular mortality risk among patients with CHD. This paradox may be related to decreased response to vitamin B12.

Uncommonly Missed Diagnosis of Methylmalonic Acidemia (MMA) in Adults and Usefulness of Testing for MMA in Cases of Seizures/Neuropathy/Weakness/Ataxia.

Methylmalonic acidemia (MMA) is a genetic condition affecting cobalamin metabolism causing elevated serum and urine methylmalonic acid without B12 deficiency. MMA presents with ketoacidotic hyperammonemic coma in newborns and can result in neonatal death or severe neurological disability. Rarely, this diagnosis is missed, or patients do not present until later in life. Presentation of this life-threatening condition is variable in adults. Improvement is rapid with IV cobalamin and a specialized diet. This case is intended to increase clinician's awareness of the late presentation of this disease and the importance of high clinical suspicion and prompt diagnosis. We present a case of a 32-year-old man with seizures, polyneuropathy, ataxia, and memory loss which were unexplained until diagnosis with MMA. We aim to help clinicians understand the variable presentation and diagnostic work-up of MMA to prevent catastrophic missed diagnoses. After an extensive work-up, the patient was found to have methylmalonic acidemia and was promptly treated with high dose vitamin B12 and a specialized diet with low protein including restricted isoleucine, threonine, methionine, and valines as well as a high caloric content. The patient showed significant clinical improvement with this treatment. To our knowledge, this is the first case of MMA presenting with these symptoms in a medically stable adult. The patient was adopted from abroad and therefore, lacked access to normal newborn screenings, further complicating diagnosis. We aim to demonstrate to clinicians the importance of considering this diagnosis in patients in whom symptoms may be suggestive, particularly if they lack access to genetic or metabolic screening.

Vitamin B12 and Folate Status in Pregnant Females and Their Infants in Norway: Secondary Analysis from the Mommy's Food Study.

BACKGROUND: Vitamin B12 and folate are essential micronutrients important for normal infant growth and development. OBJECTIVES: The aims were to describe vitamin B12 and folate status in pregnant females and their infants according to commonly used status cutoffs and examine the associations between maternal status, maternal supplement use, and breastfeeding and infant status. METHODS: Pregnant females were recruited at 18 wk gestation in Bergen, Norway. Maternal vitamin B12 and folate status were measured at gestational weeks 18 (n = 136) and 36 (n = 116), and infant status was measured at ages 3 (n = 73) and 6 (n = 74) mo. RESULTS: At gestational weeks 18 and 36, respectively, 4.4% and 2.6% of the mothers had plasma cobalamin concentrations <148 pmol/L, 0.7% and 6.9% had methylmalonic acid (MMA) concentrations >0.26 µmol/L, and 3.7% and 30% had folate concentrations <10 nmol/L. None of the females had total homocysteine (t-Hcy) concentrations >13 µmol/L or 3 combined indicator of vitamin B12 (cB12) < -0.5. At 3 and 6 mo, respectively, 4.1% and 5.4% of the infants had cobalamin concentrations <148 pmol/L, 63% and 74% had t-Hcy concentrations >6.5 µmol/L, 59% and 66% had MMA concentrations >0.26 µmol/L, and 47% and 60% had cB12 > -0.5. None of the infants had folate concentrations <10 nmol/L. Several of the vitamin B12 biomarkers in infants were associated with maternal vitamin B12 status during pregnancy. Breastfed infants had lower vitamin B12 status (as indicated by plasma cobalamin, t-Hcy, and cB12) than nonbreastfed infants at both 3 and 6 mo. Use of supplements during pregnancy was associated with better vitamin B12 status among infants at 3 and 6 mo, as indicated by infants' cobalamin and t-Hcy concentrations. CONCLUSIONS: Subclinical vitamin B12 deficiency among infants was common and associated with maternal vitamin B12 status during pregnancy and breastfeeding. Among the mothers, an increase in biochemical folate deficiency was discovered toward the end of gestation. Further studies are needed to investigate clinical consequences. This trial was registered at clinicaltrials.gov as NCT02610959.

Intake of vitamin B12 in relation to vitamin B12 status in groups susceptible to deficiency: a systematic review.

Objective: To systematically review the evidence for whether habitual or different levels of experimental intake of vitamin B12 from diet and supplements is sufficient to ensure adequate B12 status in groups most susceptible to vitamin B12 deficiency. Methods: We searched MEDLINE, Embase, Cochrane Central Register of Controlled Trials and Scopus up to 21 May 2021, for intervention studies, prospective cohort studies and case-control studies assessing B12 intake from diet and/or supplements in relation to B12 status (s/p-B12, holotranscobalamin, methylmalonic acid, homocysteine or breastmilk B12). Cross-sectional studies were eligible for studies conducted during pregnancy and lactation. Included populations were children (0-18 years), young adults (18-35 years), pregnant or lactating women, older adults (≥65 years) and vegans or vegetarians. Study selection, data extraction and risk of bias assessment were conducted by two assessors independently. The evidence was synthesized qualitatively and classified according to the World Cancer Research Fund. Results: The searches yielded 4855 articles of which 89 were assessed in full text and 18 included. Three studies were conducted during pregnancy and three during lactation or infancy - all observational. Eight studies were conducted among older adults; most were interventions among B12-deficient participants. Four studies were eligible for vegetarian and vegans, all interventions. The strength of evidence that habitual B12 intake or an intake in line with the current Nordic recommended intake (RI) is sufficient to ensure adequate status was considered Limited - no conclusion for all included populations. Conclusion: Evidence is insufficient to assess if or which level of B12 intake is sufficient to maintain adequate status for all included populations. Population-based cohort studies and low-to-moderate dose interventions that address this question are highly warranted.

Vitamin B12 in Cats: Nutrition, Metabolism, and Disease.

Cobalamin is a water-soluble molecule that has an important role in cellular metabolism, especially in DNA synthesis, methylation, and mitochondrial metabolism. Cobalamin is bound by intrinsic factor (IF) and absorbed in the ileal tract. The IF in cats is synthesized exclusively by pancreatic tissue. About 75% of the total plasma cobalamin in cats is associated with transcobalamin II, while in this species, transcobalamin I is not present. In cats, the half-life of cobalamin is 11-14 days. Diagnostic biomarkers for B12 status in cats include decreased levels of circulating total cobalamin and increased levels of methylmalonic acid. The reference interval for serum cobalamin concentrations in cats is 290-1500 ng/L, and for the serum methylmalonic acid concentration, it is 139-897 nmol/L. Therapy for hypocobalaminemia mainly depends on the underlying disease. In some cases, subcutaneous or intramuscular injection of 250 µg/cat is empirically administered. In recent years, it has been demonstrated that oral cobalamin supplementation can also be used successfully in dogs and cats as a less invasive alternative to parental administration. This review describes the current knowledge regarding B12 requirements and highlights improvements in diagnostic methods as well as the role of hypocobalaminemia in its associated diseases.

Acquired Vitamin B12 Deficiency in Newborns: Positive Impact on Newborn Health through Early Detection.

The early diagnosis of and intervention in vitamin B12 deficiency in exclusively breastfed infants by mothers with low vitamin B12 is crucial in preventing possible irreversible neurologic damage, megaloblastic anemia, and failure to thrive. We assess the usefulness of the early detection of asymptomatic B12 deficiency related to acquired conditions and highlight the importance of monitoring serum vitamin B12 levels during pregnancy. We describe demographic, clinical, dietary, and biochemical data, including the evolution of a vitamin B12 deficiency's functional biomarkers. We enrolled 12 newborns (5 males) with an age range of 1-2 months old that were exclusively breastfed and asymptomatic. These cases were referred to our metabolic unit due to alterations in expanded newborn screening: high levels of methylmalonic acid and/or total homocysteine (tHcy). All mothers were under a vegetarian diet except three who had abnormal B12 absorption, and all presented low or borderline serum B12 level and high plasma levels of tHcy. Supplementation with oral vitB12 re-established the metabolic homeostasis of the mothers. In infants, therapy with an intramuscular injection of 1.0 mg hydroxocobalamin led to the rapid normalization of the metabolic pattern, and a healthy outcome was observed. Acquired B12 deficiency should be ruled out before proceeding in a differential diagnosis of cobalamin metabolism deficits, methylmalonic acidemia, and homocystinuria.

Effect of oral or injectable supplementation with cobalamin in dogs with hypocobalaminemia caused by chronic enteropathy or exocrine pancreatic insufficiency.

BACKGROUND: Recent studies have shown similar efficacy of oral supplementation of cobalamin compared to injectable supplementation in dogs, but few prospective, randomized studies have been published. OBJECTIVES: To evaluate efficacy of oral or injectable supplementation with cobalamin in normalizing serum cobalamin and methylmalonic acid (MMA) concentrations in dogs with hypocobalaminemia caused by either chronic enteropathy (CE) or exocrine pancreatic insufficiency (EPI). ANIMALS: Forty-six client owned dogs with hypocobalaminemia. METHODS: Prospective randomized clinical trial. Dogs were divided into 2 groups (CE or EPI), and randomized to receive oral or injectable supplementation of cobalamin. Each dog had 3 visits and serum cobalamin and MMA concentrations were measured at each visit. RESULTS: In dogs with CE, serum cobalamin concentrations increased with oral (P = .02; median 149 [range 149-231] to 733 [166-1467] ng/L, median difference 552 [95% CI: 181-899] ng/L) or injectable (P < .01; 168 [149-233] to 563 [234-965] ng/L, 367 [187-623] ng/L) supplementation. In dogs with EPI, serum cobalamin concentrations increased with oral (P = .01; 162 [149-214] to 919 [643-3863] ng/L, 705 [503-3356] ng/L) or injectable (P = .01; 177 [149-217] to 390 [243-907] ng/L, 192 [89-361] ng/L) supplementation. Serum MMA concentrations decreased with oral or injectable supplementation in dogs with CE, but only with oral supplementation in dogs with EPI. CONCLUSIONS AND CLINICAL IMPORTANCE: Oral supplementation is an alternative for cobalamin supplementation in dogs with hypocobalaminemia caused by CE or EPI.

Adequate vitamin B12 and folate status of Norwegian vegans and vegetarians.

Plant-based diets may increase the risk of vitamin B12 deficiency due to limited intake of animal-source foods, while dietary folate increases when adhering to plant-based diets. In this cross-sectional study, we evaluated the B12 and folate status of Norwegian vegans and vegetarians using dietary B12 intake, B12 and folic acid supplement use, and biomarkers (serum B12 (B12), plasma total homocysteine (tHcy), plasma methylmalonic acid (MMA) and serum folate). Vegans (n 115) and vegetarians (n 90) completed a 24-h dietary recall and a FFQ and provided a non-fasting blood sample. cB12, a combined indicator for evaluation of B12 status, was calculated. B12 status was adequate in both vegans and vegetarians according to the cB12 indicator; however 4 % had elevated B12. Serum B12, tHcy, MMA concentrations and the cB12 indicator (overall median: 357 pmol/l, 9·0 µmol/l, 0·18 µmol/l, 1·30 (cB12)) did not differ between vegans and vegetarians, unlike for folate (vegans: 25·8 nmol/l, vegetarians: 21·6 nmol/l, P = 0·027). Serum B12 concentration < 221 pmol/l was found in 14 % of all participants. Vegetarians revealed the highest proportion of participants below the recommended daily intake of 2 µg/d including supplements (40 v. 18 %, P < 0·001). Predictors of higher serum B12 concentrations were average daily supplement use and older age. Folate deficiency (< 10 nmol/l) was uncommon overall (< 2·5 %). The combined indicator cB12 suggested that none of the participants was B12-depleted; however, low serum B12 concentration was found in 14 % of the participants. Folate concentrations were adequate, indicating adequate folate intake in Norwegian vegans and vegetarians.

Association Between Methylmalonic Acid and Cognition: A Systematic Review and Meta-Analysis.

Background: Methylmalonic acid (MMA) is an intermediate metabolite of human body. The content of MMA in the blood of healthy people is very low, and its concentration will increase in some diseases and elderly people. Recent studies have shown that MMA has a variety of biological functions. The correlation between MMA and cognition, one of the important functions of the nervous system, is still uncertain. Objective: Meta-analyses were performed to assess whether elevated MMA was associated with the risk of cognitive decline. Materials and Methods: Cross-sectional studies, randomized controlled studies, and case-control studies on the relationship between MMA and cognition were obtained by searching PubMed, Web of Science, EMBASE, ProQuest, WANFANG MED ONLINE, China National Knowledge Infrastructure (CNKI) and Chongqing VIP until May 2022. Two researchers independently selected studies according to inclusion and exclusion criteria, evaluated study quality and extracted data. Meta-analyses were performed using Review Manager 5.4 software. The sensitivity analysis of meta-analysis was performed by One by one exclusion method. Results: A total of 11 studies were included, including six cross-sectional studies, two randomized controlled studies, and three case-control studies, with a sample of 16,533 subjects. Meta-analysis showed that there was no significant difference in cognitive level between high-level MMA subjects and low-level MMA subjects in the general population [SMD = -2.19, 95% CI (-4.76 ∼ 0.38), Z = 1.67, P = 0.09]. In the population supplemented with VitB12, the increase of MMA level caused by VitB12 supplementation was not related to the change of cognition [SMD = 0.32, 95% CI (-0.19 ∼ 0.84) z = 1.22, P = 0.22]. There was also no significant difference in MMA levels between patients with dementia and the control group [WMD = 20.89, 95% CI (-5.13 ∼ 46.92), z = 1.57, P = 0.12]. Conclusion: In the general population, whether VitB12 is supplemented or not, there is no correlation between the increase of MMA level and the decrease of cognitive level. In dementia diseases, the level of MMA did not change significantly. High levels of MMA may not be a risk factor for cognitive impairment. The exact relationship between MMA and cognition needs further research. Systematic Review Registration: [https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42021266310], identifier [CRD42021266310].

Nitrous Oxide/Whippits-Induced Thoracic Spinal Cord Myelopathy and Cognitive Decline With Normal Serum Vitamin B12.

Abuse of nitrous oxide leads to irreversible neurologic deficits. Nitrous oxide is commonly abused through the inhalation of whipped cream canisters. These whipped cream chargers, also known as "whippits," are widely available in the United States and their sale is unregulated. There is an increasing prevalence of whippet abuse, and many are unaware of the catastrophic effects. The mechanism of injury is mediated through severe depletion of vitamin B12. Here, we report a case of nitrous oxide abuse leading to thoracic cord myelopathy. The patient has been inhaling approximately 80-100 nitrous oxide canisters daily for three months total. A magnetic resonance imaging (MRI) of the spinal cord illustrates the lesion within the thoracic cord. Further diagnostic workup with serum vitamin B12 levels was normal. However, elevated levels of methylmalonic acid (MMA) were seen. Despite supplementation of vitamin B12, the patient's neurologic deficits persisted, and he was referred to a rehabilitation center. The abuse of whippets is a serious public health threat and warrants greater regulation of their sale. MMA and holotranscobalamin (holoTC) are improved biomarkers for diagnosing vitamin B12 deficiency.

Recreational Nitrous Oxide-Induced Subacute Combined Degeneration.

Subacute combined degeneration (SCD) is myelopathy caused by vitamin B12 deficiency, leading to demyelination of the dorsal column located in the posterior spinal cord. Despite the high prevalence of recreational nitrous oxide use, its detrimental effects, including significant nerve dysfunction, are insufficiently recognized. We present the case of a 32-year-old male who was brought to the emergency department with complaints of paresthesia of his four extremities and lower extremity weakness. He was found to have B12 deficiency from chronic nitrous oxide abuse and responded positively to intramuscular B12 supplementation. It is important to consider possible nitrous oxide abuse while investigating suspected B12 deficiency, especially in patients presenting with nonspecific myeloneuropathy. Elevated methylmalonic acid (MMA) level is specific for diagnosing B12 deficiency. Prompt diagnosis and treatment can lead to the resolution of the symptoms and prevent further nerve damage.

Vitamin B-12 Intake from Dairy but Not Meat Is Associated with Decreased Risk of Low Vitamin B-12 Status and Deficiency in Older Adults from Quebec, Canada.

BACKGROUND: Vitamin B-12 deficiency can result in irreversible neurologic damages. It is most prevalent among older adults (∼5%-15%), mainly due to impaired absorption. Vitamin B-12 bioavailability varies between food sources, so their importance in preventing deficiency may also vary. OBJECTIVES: Using the NuAge Database and Biobank, we examined the associations between vitamin B-12 intake (total and by specific food groups) and low vitamin B-12 status and deficiency in older adults. METHODS: NuAge-the Quebec Longitudinal Study on Nutrition and Successful Aging-included 1753 adults aged 67-84 y who were followed 4 y. Analytic samples comprised 1230-1463 individuals. Dietary vitamin B-12 intake was assessed annually using three 24-h dietary recalls. Vitamin B-12 status was assessed annually as low serum vitamin B-12 (<221 pmol/L), elevated urinary methylmalonic acid (MMA)/creatinine ratio (>2 µmol/mmol), and a combination of both (deficiency). Vitamin B-12 supplement users were excluded. Multilevel logistic regressions, adjusted for relevant confounders, were used. RESULTS: Across all study years, 21.8%-32.5% of participants had low serum vitamin B-12, 12.5%-17.0% had elevated urine MMA/creatinine, and 10.1%-12.7% had deficiency. Median (IQR) total vitamin B-12 intake was 3.19 µg/d (2.31-4.37). Main sources were "dairy" and "meat, poultry, and organ meats." The ORs (95% CIs) in the fifth quintile compared with the first of total vitamin B-12 intake were as follows: for low serum vitamin B-12, 0.52 (0.37, 0.75; P-trend < 0.0001); for elevated urine MMA/creatinine, 0.63 (0.37, 1.08; P-trend = 0.091); and for vitamin B-12 deficiency, 0.38 (0.18, 0.79; P-trend = 0.006). Similarly, ORs (95% CIs) in the fourth quartile compared with the first of dairy-derived vitamin B-12 intake were 0.46 (0.32, 0.66; P-trend < 0.0001), 0.51 (0.30, 0.87; P-trend = 0.006), and 0.35 (0.17, 0.73; P-trend = 0.003), respectively. No associations were observed with vitamin B-12 from "meat, poultry, and organ meats." CONCLUSIONS: Higher dietary vitamin B-12 intake, especially from dairy, was associated with decreased risk of low vitamin B-12 status and deficiency in older adults. Food groups might contribute differently at reducing risk of deficiency in older populations.

Clinical relevance of testing for metabolic vitamin B12 deficiency in patients with polyneuropathy.

OBJECTIVE: Determine vitamin B12 threshold levels below which additional testing of methylmalonic acid (MMA) and/or homocysteine (Hcy) is useful to diagnose metabolic vitamin B12 deficiency in patients with polyneuropathy, and how vitamin B12, MMA and Hcy levels relate to the effect of supplementation therapy. METHODS: In a retrospective cohort study of 331 patients with polyneuropathy, vitamin B12, MMA and Hcy were measured. Linear regression models with vitamin B12 as dependent and Hcy or MMA as covariate were compared, to assess which was best related to vitamin B12. Threshold vitamin B12 levels for metabolic deficiency (defined as elevatede metabolites) were determined using logistic regression with elevated metabolites as dependent and vitamin B12 as covariate. A structured interview was conducted in 42 patients to evaluate response to vitamin B12 supplementation. RESULTS: MMA was best related to vitamin B12. Using elevated MMA for metabolic deficiency, we found 90% sensitivity at a vitamin B12 threshold level <264 pmol/L (358 pg/mL) and 95% sensitivity at <304 pmol/L (412 pg/mL). Improvement after supplementation was reported by 19% patients and stabilization by 24%. 88% of patients with improvement and 90% with stabilization either had absolute deficiency (Vitamin B12 < 148 pmol/L) or metabolic deficiency (elevated MMA and vitamin B12 ≥ 148 pmol/L). There were no additional patients with improvement or stabilization with isolated elevated Hcy. CONCLUSION: Testing of MMA has additional value in identifying patients with clinically relevant metabolic deficiency when vitamin B12 is below 304 pmol/L (412 pg/mL). Supplementation can be effective in patients with absolute and metabolic deficiency.

Plasma Methylmalonic Acid Concentration in Folic Acid-Supplemented Depressed Patients with Low or Marginal Vitamin B-12: A Randomized Trial.

BACKGROUND: Individuals with low serum vitamin B-12 and high serum folate have higher plasma concentrations of methylmalonic acid (MMA). Whether folic acid (FA) causes an increase in MMA is not known. OBJECTIVES: We aimed to determine the impact of FA supplementation on plasma MMA concentration in people with low or marginal serum vitamin B-12. METHODS: We conducted a multicenter double-blind placebo-controlled randomized trial of oral FA (5 mg/d for 12 wk) in middle-aged patients treated with antidepressant medication participating in the FoLATED (Folate Augmentation of Treatment-Evaluation for Depression) trial. Participants defined as having "low" serum vitamin B-12 (vitamin B-12 ≥150 and <220 ng/L) or "marginal" serum vitamin B-12 (vitamin B-12 ≥ 220 and <280 ng/L) were included. The primary outcome of this substudy was MMA at week 12. A mixed-effects linear regression was fitted and reported using the adjusted mean difference (aMD). RESULTS: A total of 177 participants were included (85 randomly assigned to placebo and 92 to FA); the mean ± SD age was 46.2 ± 11.8 y, and 112 (63.3%) were female. The MMA analysis included 135 participants and the aMD was -0.01 (95% CI: -0.06, 0.04; P = 0.71). Serum folate was measured on 166 participants and increased in the supplementation group; the aMD was 21.6 µg/L (95% CI: 8.13, 25.02 µg/L; P < 0.001). A total of 117 participants were assessed for RBC folate, which also increased in the supplementation group; the aMD was 461 µg/L (95% CI: 387, 535 µg/L; P < 0.001). CONCLUSIONS: Supplementation of FA leads to an increase of serum and RBC folate, but does not change plasma MMA concentration in individuals with serum vitamin B-12 between 150 and 280 ng/L. We cannot exclude effects in older people or those with serum vitamin B-12 <150 ng/L. Previously reported associations may arise from effects of impaired vitamin B-12 status on folate metabolism.This trial was registered at www.isrctn.com as ISRCTN37558856.

Vitamin B12 status in health and disease: a critical review. Diagnosis of deficiency and insufficiency - clinical and laboratory pitfalls.

Vitamin B12 (cobalamin) is an essential cofactor for two metabolic pathways. It is obtained principally from food of animal origin. Cobalamin becomes bioavailable through a series of steps pertaining to its release from dietary protein, intrinsic factor-mediated absorption, haptocorrin or transcobalamin-mediated transport, cellular uptake, and two enzymatic conversions (via methionine synthase and methylmalonyl-CoA-mutase) into cofactor forms: methylcobalamin and adenosylcobalamin. Vitamin B12 deficiency can masquerade as a multitude of illnesses, presenting different perspectives from the point of view of the hematologist, neurologist, gastroenterologist, general physician, or dietician. Increased physician vigilance and heightened patient awareness often account for its early presentation, and testing sometimes occurs during a phase of vitamin B12 insufficiency before the main onset of the disease. The chosen test often depends on its availability rather than on the diagnostic performance and sensitivity to irrelevant factors interfering with vitamin B12 markers. Although serum B12 is still the most commonly used and widely available test, diagnostics by holotranscobalamin, serum methylmalonic acid, and plasma homocysteine measurements have grown in the last several years in routine practice. The lack of a robust absorption test, coupled with compromised sensitivity and specificity of other tests (intrinsic factor and gastric parietal cell antibodies), hinders determination of the cause for depleted B12 status. This can lead to incorrect supplementation regimes and uncertainty regarding later treatment. This review discusses currently available knowledge on vitamin B12, informs the reader about the pitfalls of tests for assessing its deficiency, reviews B12 status in various populations at different disease stages, and provides recommendations for interpretation, treatment, and associated risks. Future directions for diagnostics of B12 status and health interventions are also discussed.

Vitamin B12 supplementation orally and intramuscularly in people with obesity undergoing gastric bypass.

PURPOSE: Although bariatric surgery can facilitate weight loss and improve many diseases, it impairs the absorption of many vitamins and micronutrients. Vitamin B12 is important for these patients and should be controlled and supplemented postoperatively. The aim of this paper is to compare serum vitamin B12 levels in two forms of supplementation (oral vs. intramuscular) for 6 months after gastric bypass. METHODS: In a prospective controlled cohort study, people with obesity patients undergoing gastric bypass received vitamin B12 supplementation either orally or intramuscularly. The patients were followed for 6 months, receiving serial doses of vitamin B12 and methylmalonic acid assessment at 6 months. RESULTS: A total of 53 patients were divided into two homogeneous groups: an oral group (n=24) and an intramuscular group (n=29). Serum vitamin B12 was measured preoperatively and postoperatively at 1, 2, 3, and 6 months. Serum methylmalonic acid was measured at 6 months. At each point, the serum vitamin B12 level remained within reference values in both groups, although it was higher in the oral group (p<0.001). Methylmalonic acid also remained within reference values in both groups, with no significant differences. CONCLUSION: Despite the anatomical and functional alterations that impair vitamin B12 absorption after gastric bypass, oral vitamin B12 supplementation was as effective as intramuscular in this population.

Assessment of Vitamin B12 Deficiency and Risk Factors in Healthy Infants.

OBJECTIVE: To study vitamin B12 deficiency in apparently healthy infants and their mothers and assess the risk factors. METHODS: A hospital-based, cross-sectional, observational study was conducted from July 2016 through December 2017. Consecutive healthy and normally developing infants were enrolled. Red blood cell folate, plasma vitamin B12, homocysteine and methylmalonic acid levels of mothers and infants were assessed. RESULTS: Seventy-four healthy infants were enrolled. Male-to-female ratio was 1.5:1. Anemia in 66.2% (n = 49), low plasma B12 in 17.6% (n = 13), hyperhomocysteinemia in 48.6% (n = 36), plasma methylmalonic acid in 100% (n = 74) and 'confirmed' B12 deficiency in 38% (n = 28) infants were noted. The proportion of hyperhomocysteinemia increased to 75.7% (n = 56) infants using a lower cut-off of >10 µmol/L. In mothers, low B12 in 19%, hyperhomocysteinemia in 57% and elevated plasma methylmalonic acid in 100% were noted. Median plasma B12 level was 314 pg/ml (IQR 221-421), median plasma homocysteine 15.4 µmol/L (IQR 11.3-21.7) and median plasma methylmalonic acid was 8.28 µmol/L (IQR 4.4-13.1) in mothers. Folate deficiency was noted in 9.4% infants and 12% of mothers. Overall, 63.5% mothers were vegetarian and, 64% of the mothers of infants with confirmed vitamin B12 deficiency were pure vegetarians. Odds of developing vitamin B12 deficiency increased by more than 5 times in those whose mothers' serum vitamin B12 levels were low as compared to normal maternal vitamin B12 levels (OR 5.42; 95% CI: 1.96-16.6; p 0.002). CONCLUSIONS: There is a high prevalence of vitamin B12 deficiency in infants and their mothers. There is urgent need to supplement our population with vitamin B12.

Diagnostic Challenges Using a 2-Tier Strategy for Methylmalonic Acidurias: Data from 1.2 Million Dried Blood Spots.

BACKGROUND: The detection of methylmalonic acid (MMA) by second-tier analysis has been shown to reduce the number of false positives in newborn screening (NBS) for genetically determined methylmalonic acidurias (MMAuria). In addition to genetic conditions, MMA is an indicator of vitamin B12 status, thus applicable to detect maternal vitamin B12 deficiency in the newborns screened. METHODS: Biochemical and clinical follow-up data of a 7.5-year pilot study with 1.2 million newborns screened were reviewed. RESULTS: Among 1,195,850 NBS samples, 3,595 (0.3%) fulfilled criteria for second-tier analysis of MMA. In 37 (0.003%; 1/32,000) samples, elevated concentrations of MMA were detected, resulting in diagnostic workup at a metabolic center in 21 newborns. In 6 infants (1/199,000), genetic conditions were established, 1 infant with cobalamin C deficiency (CblC) showed only a moderate elevation of MMA. The remaining 15 newborns (1/79,000) displayed significantly lower concentrations of MMA and were evaluated for maternal vitamin B12 deficiency. In 9 mothers, vitamin B12 deficiency was verified, and 6 showed no indication for vitamin B12 deficiency. Treatment with vitamin B12 normalized biochemical parameters in all 15 infants. CONCLUSIONS: Applying a 2-tier strategy measuring MMA in NBS identified genetic conditions of MMAuria. It was possible to separate severe, early-onset phenotypes from maternal vitamin B12 deficiency. However, the detection of CblC deficiency with mildly elevated MMA interferes with impaired vitamin B12 status of unknown relevance and thus burdens possibly healthy newborns. Regarding maternal vitamin B12 deficiency, testing and supplementing mothers-to-be is preferable. This might decrease straining follow-up of newborns and improve quality and overall perception of NBS.

Mass spectrometry analysis of urinary methylmalonic acid to screen for metabolic vitamin B12 deficiency in older adults.

Aim: Vitamin B12 deficiency is characterized metabolically by increased serum and urine methylmalonic acid (MMA). Urinary MMA/creatinine ratio is suggested for screening for metabolic vitamin B12 deficiency in older populations. Results: A UPLC-MS/MS method for the analysis of urinary MMA and creatinine was developed/validated. A good separation of MMA from succinic acid, its structural isomer, was achieved. Intra- and interday accuracy biases and precision coefficients were all ≤6.3% for MMA and creatinine. Urine and serum samples of 34 individuals of the NuAge Biobank were analyzed for technical comparisons showing that urinary MMA/creatinine ratios by UPLC-MS/MS strongly correlated with GC-MS values, and with serum MMA values. Conclusion: The UPLC-MS/MS method developed is rapid/reliable for the analysis of urinary MMA/creatinine ratios.

Dietary Intake and Biomarkers of Folate and Cobalamin Status in Norwegian Preschool Children: The FINS-KIDS Study.

BACKGROUND: Folate and cobalamin (vitamin B-12) are essential for growth and development. However, few population-based studies have investigated B-vitamin status in children. OBJECTIVES: This study aimed to assess biomarkers of folate and vitamin B-12 status and to explore their dietary determinants in healthy Norwegian children. METHODS: Using baseline data obtained from a randomized controlled trial on the effect of fish intake on neurodevelopment in children aged 4-6 y, we measured the plasma concentrations of folate, cobalamin, total plasma homocysteine (tHcy), and methylmalonic acid (MMA). Food-frequency questionnaires (FFQs) were used to assess dietary intake. We used unadjusted and multiple linear regression models to explore the determinants of biomarker concentrations. RESULTS: The median (IQR) of plasma folate (n = 197) and plasma cobalamin (n = 195) concentrations were 15.2 (12.2-21.1) nmol/L and 785 (632-905) pmol/L, respectively. Plasma folate concentrations of <10 nmol/L were observed in 13% of the children. No child had a cobalamin concentration <148 pmol/L. Two children were identified with elevated plasma MMA concentrations (>0.26 µmol/L) and 8 children had elevated tHcy concentrations (>6.5 µmol/L). Plasma folate concentration was inversely correlated with tHcy (ρ = -0.24, P < 0.001); we found no correlation between tHcy and cobalamin (ρ = -0.075, P = 0.30). Children who consumed vitamin supplements had 51% higher plasma folate concentrations (P < 0.0001) than those who did not. Consumption of red meat for dinner more than twice a week was associated with 23% lower plasma folate (P < 0.01). No other significant associations between dietary intake and the biomarkers were observed. CONCLUSIONS: The Norwegian preschool children from this cohort had adequate vitamin B-12 status. Poor folate status was common and associated with elevated tHcy. The implications of poor folate status during childhood should be a prioritized research question. This trial was registered at ClinicalTrials.gov as NCT02331667.