Much of the research into the importance of folic acid and B12 levels has centered on seniors, and there is now quite a lot of research pointing to the need for adequate levels of these vitamins for maintaining cognitive functioning as you get older. In particular, high levels of homocysteine increase the risk of developing Alzheimer’s, and these go hand-in-hand with low levels of B12 and folic acids. Homocysteine is produced by the breakdown of a dietary protein called methionine, and B-vitamins are required to convert homocysteine back to methionine.

Excitingly, though, a study found that vitamin B supplements markedly reduced brain atrophy in older adults with mild cognitive impairment, offering hope that they may be effective in delaying the development of Alzheimer’s. The benefits were greatest for those with the highest levels of homocysteine.

Folic acid levels are of course also regarded as crucial when the brain is developing, which is why pregnant women are urged to take supplements, and why some countries fortify their bread with it.