B vitamins are good for the brain and may help reduce Alzheimer’s risk.  There is an association with high homocysteine levels in the blood and risk of Alzheimer’s.  Not getting enough B vitamins in one possible reason for high homocysteine.  This is especially true of vitamin B12 since we are less able to absorb it as we age.

FoodForTheBrain.org writes …

“… risk of dementia and Alzheimer’s could be reduced in the early stages by a comprehensive optimum nutrition approach. The strongest evidence to date relates to raised homocysteine levels, which both predicts risk and can cause the kind of brain damage seen in Alzheimer’s, caused by lack of B vitamins, especially B12 which is increasingly poorly absorbed with age.”

Dr. Mark Hyman says in this video where he gave a talk at Google …

“Your brain runs on nutrients … and if you don’t have adequate levels of nutrients, you can’t actually regulate your brain function properly. So, having adequate levels of nutrients, particularly the methylating nutrients, B6, folate, B12, vitamin D, omega-3 fats, these are critical for brain function.”

Steven Fowkes also gave a Google Tech Talk in he also mentions about B vitamins.

Page 59 of the book The Happiness Diet has section titled “Essential Element of Happiness #1: Vitamin B12” which says …

“You can’t make brain cells without this vitamin. Low B12 causes irritability, depression, and cognitive decline”.

Dr. Terry Wahls who has multiple sclerosis places a high value on B vitamins because B1, B9, and B12 are needed to make the myelin sheaths insulating the axon of the neurons.  You can watch her TedTalk here.