Abstract
Normal and subnormal serum levels of vitamin B12 and/or folate do not exclude functional deficiency, and elderly people are specifically exposed to deficiency owing to impaired nutrition, malabsorption, accompanying diseases and current medication. Several studies report that low levels of vitamin B12 are more common in people with Alzheimer’s disease (AD) than in non-demented people. Low levels of folate are also correlated with other types of dementia. Current studies suggest that low levels of vitamin B12 as well as folate may be part of the aetiology in AD. A functional deficiency of vitamin B12/folate may be present despite serum levels within reference limits. The amino acid homocysteine (Hcy) is a sensitive but non-specific marker of deficiency of vitamin B12 and folate and appears to have the strongest association with cognitive function. The association between Hcy levels and cognitive function is also stronger than that of the levels of vitamin B12/fol ate. The clinical manifestations of vitamin B12/folate deficiency are non-specific, but when they are connected with laboratory findings adequate investigation should be performed. A generous attitude to treatment with vitamin B12/folate is advocated, combined with a compulsory evaluation of treatment effect. Clinical regress of neuropsychiatric symptoms by cobalamin and folate therapy is dependent on the duration and severity of symptoms, but on a group level, not necessarily in individual patients. Keywords: cognition; folate; homocysteine; vitamin B12
Highlights
Vitamin B12 is a water-soluble, heat-sensitive vitamin of the B-vitamin group
Since the 1950s, the focus of vitamin B12 deficiency has moved from classical haematology, through the neurological speciality to the geriatric speciality, with neuropsychiatric manifestations such as depression, mild cognitive impairment and dementia [5]
Methylmalonic acid (MMA) [8] and homocysteine (Hcy) represent two of these markers, of which Hcy has a vast body of documentation (9Á/11)
Summary
Vitamin B12 is a water-soluble, heat-sensitive vitamin of the B-vitamin group. Only microorganisms are able to synthesize vitamin B12. Diseases and dysfunction of the stomach, pancreas and intestines may affect the physiology of absorption and thereby the serum and tissue levels of vitamin B12. It is only B12 bound to transcobalamin II, holotranscobalamin, which is absorbed through the cells, while 70% is bound to haptocorrines circulating for a long time in the blood [4]. Serum levels of vitamin B12 and folate within reference limits do not exclude tissue deficiency. Methylmalonic acid (MMA) [8] and homocysteine (Hcy) represent two of these markers, of which Hcy has a vast body of documentation (9Á/11) They are intimately involved in joint metabolism with vitamin B12 and folate. There are several other causes of Hcy elevation [12, 13] (Fig. 2)
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