B6, B12, Folic acid to stop brain shrinkage?

https://www.patrickholford.com/blog/b-vitamin-supplements-stop-alzheimer-s-brain-shrinkage

"According to this research anyone with a level above 10mcmol/l can benefit from supplementing a high daily dose of B6 (20mg), B12 (500mcg) and folic acid (800mcg).

These doses, which have now been shown to stop memory loss and brain shrinkage are much higher than you can get from a good diet alone." (May 21, 2013)