Can B vitamins prevent the development of dementia?

A new UK review reports that taking supplements with folic acid and/or vitamin B12 does not slow age-related mental decline. Experts commented that these conclusions are in contrast to the well accepted benefits of B vitamins for brain health and ignore latest research.

The review analyzed the results of 11 randomized controlled trials involving about 22,000 participants which compared the effect of B vitamin supplementation on cognitive function in older people against placebo (1). The analysis showed that participants receiving folic acid and/or vitamin B12 did see a reduction in the levels of homocysteine in their blood by around 25%. However, this had no effect on their mental abilities: the measurement of specific mental processes such as memory, speed or executive function showed no significant difference between the B vitamin and the placebo groups. Increased intakes of folic acid and vitamin B12 did not show to prevent the development of Alzheimer’s disease.

The researchers noted that while taking B vitamins may not help everyone, they may have some benefits in specific groups of people with dementia. Experts commented that the benefits of adequate vitamin B6, B9 and B12 intakes for brain health and cognitive performance are well established (2–4) and have also been shown in studies (5–7), which were incomprehensibly not included in the current review. People with higher blood concentrations of the amino acid homocysteine have been shown to be at increased risk of developing Alzheimer’s disease. Increased intakes of folic acid, vitamin B6 and vitamin B12 are known to lower levels of homocysteine in the body, potentially slowing mental decline. The experts added that preventing a multifac-torial disease such as dementia may certainly need more than only increased intakes of B vitamins: Eating a healthy, balanced diet, taking regular exercise and keeping blood pressure and weight in check can all help lower the risk of Alzheimer’s.

1. Clarke R. et al. Effects of homocysteine lowering with B vitamins on cognitive aging: meta-analysis of 11 trials with cognitive data on 22,000 individuals. American Journal of Clinical Nutrition. Published online July 2014.
2. EFSA Panel on Dietetic Products, Nutrition and Allergies. Scientific Opinion on the substantiation of health claims related to vitamin B6. EFSA Journal. 2010; 8(10):1759 [24 pp.].
3. EFSA Panel on Dietetic Products, Nutrition and Allergies. Scientific Opinion on the substantiation of health claims related to folate. EFSA Journal. 2010; 8(10): 1760 [19 pp.].
4. EFSA Panel on Dietetic Products, Nutrition and Allergies. Scientific Opinion on the substantiation of health claims related to vitamin B12. EFSA Journal. 2010; 8(10):1756 [23 pp.].
5. Douaud G. et al. Preventing Alzheimer’s disease-related gray matter atrophy by B-vitamin treatment. PNAS. 2013; 110(23): 9523–9528.
6. Walker J. G. et al. Oral folic acid and vitamin B-12 supplementation to prevent cognitive decline in community-dwelling older adults with depressive symptoms – the Beyond Ageing Project: a randomized controlled trial. AJCN. 2012; 95:194–203.
7. Smith A. D. et al. Homocysteine-Lowering by B Vitamins Slows the Rate of Accelerated Brain Atrophy in Mild Cognitive Impairment: A Randomized Controlled Trial. PLOS ONE. 2010; 5(9):e12244.