These are some interesting studies about B-12 supplementation
Oral vitamin B12 versus intramuscular vitamin B12 for vitamin B12 deficiencyEditorial Group: Cochrane Metabolic and Endocrine Disorders Group
Published Online: 20 JUL 2005
Abstract
Background
Vitamin B12 deficiency is common and rises with age. Most people with vitamin B12 deficiency are treated in primary care with intramuscular vitamin B12 which is a considerable source of work for health care professionals. Several case control and case series studies have reported equal efficacy of oral administration of vitamin B12 but it is rarely prescribed in this form, other than in Sweden and Canada. Doctors may not be prescribing oral formulations because they are unaware of this option or have concerns regarding effectiveness.
Objectives
To assess the effectiveness of oral vitamin B12 versus intramuscular vitamin B12 for vitamin B12 deficiency.
Search methods
Searches were undertaken of The Cochrane Library, MEDLINE, EMBASE and Lilacs. The bibliographies of all relevant papers identified using this strategy were searched. In addition we contacted authors of relevant identified studies and Vitamin B12 research and pharmaceutical companies to enquire about other published or unpublished studies and ongoing trials.
Selection criteria
Randomised controlled trials (RCTs) examining the use of oral or intramuscular vitamin B12 to treat vitamin B12 deficiency.
Data collection and analysis
All abstracts or titles identified by the electronic searches were independently scrutinised by two reviewers. When a difference between reviewers arose, we obtained and reviewed a hard copy of the papers and made decisions by consensus. We obtained a copy of all pre-selected papers and two researchers independently extracted the data from these studies using piloted data extraction forms. The whole group checked whether inclusion and exclusion criteria were met, and disagreement was decided by consensus. The methodological quality of the included studies was independently assessed by two researchers and disagreements were brought back to the whole group and resolved by consensus.
Main results
Two RCT's comparing oral with intramuscular administration of vitamin B12 met our inclusion criteria. The trials recruited a total of 108 participants and followed up 93 of these from 90 days to four months. High oral doses of B12 (1000 mcg and 2000 mcg) were as effective as intramuscular administration in achieving haematological and neurological responses.
Authors' conclusions
The evidence derived from these limited studies suggests that 2000 mcg doses of oral vitamin B12 daily and 1000 mcg doses initially daily and thereafter weekly and then monthly may be as effective as intramuscular administration in obtaining short term haematological and neurological responses in vitamin B12 deficient patients.
Oral Cyanocobalamin Supplementation in Older People With Vitamin B12 DeficiencyA Dose-Finding TrialArch Intern Med. 2005;165(10):1167-1172.
The results of this trial indicate that the lowest dose of oral cyanocobalamin required to normalize biochemical markers of mild vitamin B12 deficiency in older people with a mild vitamin B12 deficiency is more than 200 times greater than the recommended dietary allowance for vitamin B12 of approximately 3 μg/d. Clinical trials are currently assessing the effects of high doses of oral cobalamin on markers of cognitive function and depression. If such trials can demonstrate that the reported associations of vitamin B12 deficiency with cognitive impairment or depression are causal and reversible by treatment, the relevance of correction of vitamin B12 deficiency in older people could be substantial. However, the present trial demonstrates that much higher doses of cyanocobalamin are required to normalize vitamin B12 deficiency than were previously believed.
