Cobalamin/Vitamin B12 (Cbl) is an essential vitamin, supplied mainly as hydroxocobalamin (OHCbl) by animal products, including cows' milk. Cyanocobalamin (CNCbl) is the usual form in vitamin pills. The aim was to explore absorption and tissue accumulation of two Cbl forms, administered alone or bound to milk protein.
To investigate the absorption of synthetic cyanocobalamin and natural occurring hydroxocobalamin in populations with low and normal cobalamin (vitamin B12) status.
Vitamin B12 (cyancobalamin, Cbl) has two active co-enzyme forms, methylcobalamin (MeCbl) and adenosylcobalamin (AdCbl). There has been a paradigm shift in the treatment of vitamin B12 deficiency such that MeCbl is being extensively used and promoted. This is despite the fact that both MeCbl and AdCbl are essential and have distinct metabolic fates and functions. MeCbl is primarily involved along with folate in hematopiesis and development of the brain during childhood. Whereas deficiency of AdCbl disturbs the carbohydrate, fat and amino-acid metabolism, and hence interferes with the formation of myelin. Thereby, it is important to treat vitamin B12 deficiency with a combination of MeCbl and AdCbl or hydroxocobalamin or Cbl. Regarding the route, it has been proved that the oral route is comparable to the intramuscular route for rectifying vitamin B12 deficiency.European Journal of Clinical Nutrition advance online publication, 13 August 2014; doi:10.1038/ejcn.2014.165.
- Journal of photochemistry and photobiology. B, Biology
- Published almost 7 years ago
Vitamin B12 (cobalamin) is required for proper red blood cell formation, neurologic function, and DNA synthesis. Cobalamins in solutions are light sensitive, but no comprehensive study has been performed to compare the photostability of different cobalamins under UVA exposure. Their indirect photodegradation due to their antioxidant properties and their photostability in vivo have also not been studied so far. The photodegradation of four cobalamins (methylcobalamin (MeCbl), adenosylcobalamin (AdCbl), hydroxocobalamin (OHCbl) and cyanocobalamin (CNCbl)) under UVA exposure in aqueous solutions (pH=7.4) have been investigated by absorption spectroscopy. The photodegradation of OHCbl in the absence and presence of the endogenous photosensitizer riboflavin was studied. Serum vitamin B12 concentrations before and after summer were measured in four patients with psoriasis. All studied cobalamins are photolabile. The biologically active forms of cobalamin, AdCbl and MeCbl, are converted to OHCbl within seconds during UVA exposure. OHCbl is the most stable cobalamin. However, reactive oxygen species increases the degradation rate of OHCbl. Our pilot study on humans demonstrates that serum vitamin B12 concentrations are not significantly affected during summertime in Norway. Further work is needed to determine vitamin B12 photostability in humans living at lower latitudes or using sunbeds.
B vitamin therapy for homocysteine: renal function and vitamin B12 determine cardiovascular outcomes
- Clinical chemistry and laboratory medicine : CCLM / FESCC
- Published almost 7 years ago
Abstract Therapy to lower homocysteine with B vitamins does reduce the risk of stroke, if not myocardial infarction. The apparent lack of efficacy of vitamin therapy in most of the large clinical trials was probably determined by the failure to take account of the metabolic deficiency of vitamin B12, which is very common and often missed, and by the failure to take account of impaired renal function. Metabolic B12 deficiency is present in 20% of people over 65 years of age, and in 30% of vascular patients above 70 years, so higher doses of B12 are needed in elderly patients. However, high-dose cyanocobalamin leads to accumulation of cyanide in patients with renal failure. B vitamin therapy is beneficial in patients with good renal function, but harmful in patients with significantly impaired renal function (a glomerular filtration rate <50). It seems likely that in patients with renal impairment, methylcobalamin should be used instead cyanocobalamin.
Vitamin B12 was determined and characterized in 19 dried Chlorella health supplements. Vitamin contents of dried Chlorella cells varied from < 0.1 μg to approximately 415 μg per 100 g dry weight. Subsequent liquid chromatography/electrospray ionization-tandem mass spectrometry analyses showed the presence of inactive corrinoid compounds, a cobalt-free corrinoid, and 5-methoxybenzimidazolyl cyanocobamide (factor IIIm) in four and three high vitamin B12-containing Chlorella tablets, respectively. In four Chlorella tablet types with high and moderate vitamin B12 contents, the coenzyme forms of vitamin B12 5'-deoxyadenosylcobalamin (approximately 32%) and methylcobalamin (approximately 8%) were considerably present, whereas the unnaturally occurring corrinoid cyanocobalamin was present at the lowest concentrations. The species Chlorella sorokiniana (formerly C. pyrenoidosa) is commonly used in dietary supplements and did not show an absolute requirement of vitamin B12 for growth despite vitamin B12 uptake from the medium being observed. In further experiments, vitamin B12-dependent methylmalonyl-CoA mutase and methionine synthase activities were detected in cell homogenates. In particular, methionine synthase activity was significantly increased following the addition of vitamin B12 to the medium. These results suggest that vitamin B12 contents of Chlorella tablets reflect the presence of vitamin B12 generating organic ingredients in the medium or the concomitant growth of vitamin B12-synthesizing bacteria under open culture conditions.
Vitamins are dietary components which are necessary for life. They play a major role in health and their deficiency may be linked to symptoms of psychiatric disorders. B vitamins are required for proper functioning of the methylation cycle, monoamine oxidase production, DNA synthesis and the repair and maintenance of phospholipids. Vitamin B deficiency could influence memory function, cognitive impairment and dementia. In particular, vitamins B1, B3, B6, B9 and B12 are essential for neuronal function and deficiencies have been linked to depression. We discuss the causes of depression and the neurochemical pathways in depression. In particular, we provide evidence that vitamin B contributes to the complexity of depressive symptoms.
The purpose of this narrative review is to highlight insights into the importance and frequency of metabolic vitamin B12 (B12) deficiency, reasons why it is commonly missed, and reasons for the widespread but mistaken belief that treatment of B12 deficiency does not prevent stroke or improve cognitive function. Metabolic B12 deficiency is common, being present in 10%-40% of the population; is frequently missed; is easily treated; and contributes importantly to cognitive decline and stroke in older people. Measuring serum B12 alone is not sufficient for diagnosis; it is necessary to measure holotranscobalamin or functional markers of B12 adequacy such as methylmalonic acid or plasma total homocysteine. B-vitamin therapy with cyanocobalamin reduces the risk of stroke in patients with normal renal function but is harmful (perhaps because of thiocyanate accumulation from cyanide in cyanocobalamin) in patients with renal impairment. Methylcobalamin may be preferable in renal impairment. B12 therapy slowed gray matter atrophy and cognitive decline in the Homocysteine and B Vitamins in Cognitive Impairment Trial. Undiagnosed metabolic B12 deficiency may be an important missed opportunity for prevention of dementia and stroke; in patients with metabolic B12 deficiency, it would be prudent to offer inexpensive and nontoxic supplements of oral B12, preferably methylcobalamin or hydroxycobalamin. Future research is needed to distinguish the effects of thiocyanate from cyanocobalamin on hydrogen sulfide, and effects of treatment with methylcobalamin on cognitive function and stroke, particularly in patients with renal failure.
To determine the repeatability and reproducibility figures of the AOAC First Action Official MethodSM 2014.02 (Vitamin B12 in Infant Formula and Adult/Pediatric Formula by Liquid Chromatography with UV Detection), a collaborative study was organized. Twenty-one laboratories located in 13 different countries agreed to participate. The study was divided into two parts. During the first part, the laboratories analyzed two samples in duplicate by using the method described in the protocol. The laboratories that provided results within the expected range were qualified for part two, during which they analyzed 10 samples in blind duplicates. Eighteen laboratories managed to provide results on time for reporting. The results were compared with the Standard Method Performance Requirement (SMPR® 2011.005) established for vitamin B12. The precision results met the requirements stated in the SMPR except for one sample. Repeatability and reproducibility relative standard deviation ranged from 1.1 to 6.5% and from 6.0 to 23.8%, respectively, with only one matrix showing reproducibility values higher than the required 11%. Horwitz ratio values were all well below 2 (0.17-0.78). The AOAC Expert Review Panel (Stakeholder Panel for Infant Formula and Adult Nutritional Expert Review Panel) determined that the data presented met the SMPR and, hence, recommended the method to be granted Final Action status in September 2016.
To determine the prevalence and possible factors associated with anaemia, and vitamin B12 and folate deficiencies in women of reproductive age (WRA) in Pakistan.