Claims vitamin B prevents Alzheimer's are unproven
'Should you be taking vitamin B to protect against Alzheimer's?,' asks the Daily Mail.
Its question is prompted by new research into whether a daily dose of vitamin B could reduce the loss of brain tissue in people with mild cognitive impairment. Mild cognitive impairment is thought to be a risk factor for developing Alzheimer’s disease.
The researchers were particularly interested in the effects of B vitamins on ‘grey matter’ – brain tissue. Grey matter consists of a complex mixture of nerve cells and is found in regions of the brain associated with higher cognitive functions, such as memory and reasoning. Previous studies have found that in people with Alzheimer’s disease, certain regions of grey matter begin to shrink, and this may contribute towards the symptoms of the disease.
This research clearly shows that grey-matter loss in certain regions of the brain was reduced with B vitamin treatment – and the results were particularly striking in patients with high levels of an amino acid called homocysteine.
However, whether the reduction in grey matter shrinkage caused by the vitamin B treatment reduced the likelihood of participants developing Alzheimer’s disease, is unknown.
Until further trials have confirmed the benefits of B vitamin supplements and found that they outweigh any potential harms, the best way to keep healthy in mind and body is to eat a balanced diet, control your weight and blood pressure, and to take some exercise.
Where did the story come from?
The study was carried out by researchers from the University of Oxford, the University of Warwick, and the University of Oslo, Norway. It was funded by a wide range of charitable organisations and research institutes.
The study was published in the peer-reviewed Proceedings of the National Academy of Sciences of the United States of America (PNAS).
This story was widely reported in the media. The Daily Express went with the headline “The daily vitamin B pill that halts the ravages of dementia” and The Daily Telegraph with “Vitamin B could stave off Alzheimer’s”. Unfortunately, these headlines are a little optimistic, as although the study found that vitamin B reduced loss of grey matter in certain parts of the brain, especially in older people with high levels of the amino acid homocysteine, the effects this reduction had on an individual’s risk of developing Alzheimer’s disease were not assessed.
What kind of research was this?
This was a randomised controlled trial that aimed to determine whether B vitamins are effective in preventing the shrinkage of grey matter in areas of the brain known to be vulnerable to Alzheimer’s disease, especially those regions linked to mental processes.
This was a secondary analysis of data collected in a previous study which found that B vitamins reduce whole volume brain shrinkage.
A randomised controlled trial is the best type of study design to address this question.
What did the research involve?
The researchers randomised 156 elderly volunteers with memory complaints who fulfilled criteria for mild cognitive impairment to receive B vitamin treatment (folic acid 0.8mg/day, vitamin B12 0.5mg/day, vitamin B6 20mg/day) or placebo for 24 months.
Images of the participants’ brains were taken at the start and end of the study using magnetic resonance imaging (MRI). The researchers compared the images to see whether B vitamins prevented shrinkage of grey matter in areas of the brain affected by the Alzheimer’s disease, especially those regions linked to mental processes.
What were the basic results?
Grey matter volumes were similar at the start of the study in both groups. Over the course of the study, areas of grey matter shrunk in both the placebo and B vitamin groups. However, participants who received B vitamins had less shrinkage of certain areas of grey matter than participants who received placebo.
The researchers report that significant reductions in grey matter loss were seen in some of the regions most affected in Alzheimer’s disease.
The researchers drew on the results of previous research, which has found that levels of an amino acid called homocysteine may play a role in cognitive impairment, Alzheimer’s disease and vascular dementia.
They found that participants with higher homocysteine levels had smaller brain volume, and a faster reduction in brain size.
B vitamin treatment had no effect in participants who had homocysteine levels below the median (average), but significantly reduced grey matter loss in participants with homocysteine levels above the median.
The researchers also monitored changes in participants’ scores on a variety of neuropsychological scales. They found that scores were correlated with grey matter loss in certain regions, some of which shrunk less with vitamin-B treatment than placebo in participants with high homocysteine levels.
Based on these findings, the researchers suggest that changes in vitamin B12 levels that occur with B vitamin treatment leads to a reduction in homocysteine levels. This decreases the rate of grey matter loss. This in turn affects neuropsychological functioning.
How did the researchers interpret the results?
The researchers conclude that, “our results show that B-vitamin supplementation can slow the atrophy [shrinkage] of specific brain regions that are a key component of the Alzheimer’s disease process and that are associated with cognitive decline.”
They go on to suggest that “further B vitamin supplementation trials focusing on elderly subjects with high homocysteine levels are warranted to see if progression to dementia can be prevented.”
Conclusion
This two-year long randomised controlled trial found that B vitamin treatment significantly reduces loss of grey matter in certain regions of the brain in elderly volunteers with mild cognitive impairment. The researchers report that these regions are specifically vulnerable to Alzheimer’s disease. B vitamin treatment was beneficial for the subgroup of participants who had higher than average levels of an amino acid called homocysteine.
This research clearly shows that grey matter loss in certain regions of the brain was reduced with B vitamin treatment. This follows on from the researchers’ previous findings that B vitamin treatment slows brain shrinkage.
However, it is less clear whether the reduction in grey matter actually had any real health impact on individual people. Although the researchers report that loss of grey matter was linked to declining neuropsychological scores, they do not specifically report that participants who received the B vitamins improved their brain function scores. Whether the B vitamin treatment actually prevented Alzheimer’s disease is also unknown.
B vitamins are a recurring focus of Alzheimer’s disease research, and they have been studied in both the prevention and treatment of the disease. This may partly be because vitamin B deficiency can have an effect on brain function.
