Long-term usage of antiepileptic drugs (AED) may lead to changes in serum vitamin B12 (B12) levels. Studies show that after sodium valproate prescription in epileptic patients, B12 concentrations increased.1 On the other hand, in the normal population, serum levels of B12 decreases with age.2 In the case of B12 deficiency, various hematologic, neurologic, and psychiatric clinical findings may b...

OBJECTIVES This study aims to assess the usefulness of serum holotranscobalamin (holoTC), the fraction of vitamin B12 that is available for tissue uptake, compared with total vitamin B12 in patients investigated for vitamin B12 disorders. METHODS Serum samples were randomly selected from 76 patients (48 females, 28 males; age range 12-69 years) referred to the Clinical Biochemistry Laboratory...

BACKGROUND Profound vitamin B12 deficiency is a known cause of disease, but the role of low or intermediate levels of B12 in the development of neuropathy and other neuropsychiatric symptoms, as well as the relationship between eating meat and B12 levels, is unclear. OBJECTIVE The objective of our study was to investigate the role of low or intermediate levels of B12 in the development of neu...

Several observations suggest that the absorption of vitamin B12 may be inhibited by bacteria. Both in experimental animals and in patients with blind loops, strictures, or fistulae involving the small intestine, heavy growths of bacteria have been found in areas of the bowel which are normally sterile (Seyderhelm, Lehmann, and Wichels, 1924; Doig and Girdwood, 1960). In patients with such lesio...

I N THE PAST SEVERAL YEARS a number of radioassay procedures for serum vitamin B12 have been described. Each method is based on the fact that unlabeled crystalline B12 will competitively inhibit isotopically labeled B12 (tracer B12) from binding to a specific B12 binding protein(s). Basic to each procedure is the reaction of B12 (labeled and unlabeled) with a limited quantity of binding protein...

Metformin treatment, both duration and dose, is associated with increased risk of vitamin B12 (B12) deficiency. B12 deficiency causes Hyperhomocysteinemia (HHcy), which is associated with an increased risk of a variety of diabetic co-morbidities. As a result, the newest “Standards of Medical Care in Diabetes 2017”, issued by the American Diabetes Association included a recommendation to periodi...

279 14.1 Role of vitamin B12 in human metabolic processes Although the nutritional literature still uses the term vitamin B12, a more specific name for vitamin B12 is cobalamin. Vitamin B12 is the largest of the B complex vitamins, with a relative molecular mass of over 1000. It consists of a corrin ring made up of four pyrroles with cobalt at the centre of the ring (1, 2). There are several vi...

In cobaiamin deficiency, inadequate DNA-thymine synthesis appears to resuit from decreased conversion of N5methyltetrahydrofolic acid to tetrahydrofo ic acid (THE). The N5-methyl THE conversion catalyzed by N5methyl THF-homocysteine methyltransferase requires a cobalamin coenzyme, presumed to be methylcobalamin (methyl-B12). In support of the above, in B12-deficient marrow cultures, methyl-B12 ...

Vitamin B12 deficiency is common in older people and is associated with cognitive impairment in the absence of anaemia or macrocytosis [1–3]. The prevalence of vitamin B12 deficiency increases in the elderly, mainly due to malabsorption of food-bound vitamin B12 due to atrophic gastritis that limits the ability of older people to release vitamin B12 from dietary sources in meat, fish and dairy ...