The study, published in the American Journal of Clinical Nutrition, reports on a trial of 201 people aged over 75 years with moderate vitamin B12 deficiency who received either vitamin B12 or a placebo supplements for one year – finding no evidence of improved neurological or cognitive function among people who received vitamin B12 compared to those who received the placebo tablets.
The team, led by Dr Alan Dangour at the London School of Hygiene & Tropical Medicine, noted that while there is clear evidence that individuals with severe vitamin B12 deficiency (with or without anaemia) benefit significantly from treatment, there is uncertainty about the relevance of vitamin B12 treatment in non-anaemic individuals with moderate vitamin B12 levels.
"This is the first trial of the effect of vitamin B12 supplementation on neurological and cognitive function in older people with moderate vitamin B12 deficiency,” said Dangour. “Many people may be taking vitamin B12 supplements on a regular basis and it has been thought they would enhance function in older people. Our study found no evidence of benefit for nervous system or cognitive function from 12 months of supplementation among older people with moderate vitamin B12 deficiency.”
Around one sixth of people in the UK aged over 75 have vitamin B12 deficiency, which when severe can lead to significant problems in the nervous system including muscle weakness, problems with walking, tiredness, and pins and needles, as well as depression and problems with memory and other important everyday cognitive functions.
Previous studies have suggested that people with moderate vitamin B12 deficiency have poorer nerve and memory functions, but that the effects of daily supplementation with vitamin B12 to correct moderate deficiency on nervous system function were previously unknown.
Dangour and his colleagues investigated whether vitamin B-12 supplementation benefits neurologic and cognitive function in moderately vitamin B-12–deficient older people. The double-blind, randomised, placebo-controlled trial enrolled 201 participants from 7 general practices in South East England.
The 201 participants received 1 mg crystalline vitamin B-12 or a matching placebo as a daily oral tablet for 12 months, while Peripheral motor and sensory nerve conduction, central motor conduction, a clinical neurologic examination, and cognitive function were assessed before and after treatment.
The team revealed that compared with baseline, allocation to vitamin B-12 was associated with a 177% increase in serum concentration of vitamin B-12 (641 compared with 231 pmol/L), a 331% increase in serum holotranscobalamin (240 compared with 56 pmol/L), and 17% lower serum homocysteine (14.2 compared with 17.1 μmol/L).
“In intention-to-treat analysis of covariance models, with adjustment for baseline neurologic function, there was no evidence of an effect of supplementation on the primary outcome of the posterior tibial compound muscle action potential amplitude at 12 mo (mean difference: −0.2 mV; 95% CI: –0.8, 0.3 mV),” said the team. “There was also no evidence of an effect on any secondary peripheral nerve or central motor function outcome, or on cognitive function or clinical examination.”
Indeed, the team concluded that the results of the trial do not support the idea that the correcting a moderate vitamin B-12 deficiency has beneficial effects on neurologic or cognitive function in later.
Source: American Journal of Clinical Nutrition
Published online ahead of print, doi: 10.3945/ajcn.115.110775
“Effects of vitamin B-12 supplementation on neurologic and cognitive function in older people: a randomized controlled trial”
Authors: Alan D Dangour, et al