B vitamins are a group of eight different nutrients that work together to manage many processes in the body, including stress levels. Vitamin B12 deficiency can cause a number of neurological symptoms, including instability, neuropathy and cognitive defects. A 2017 study found that people who had lower blood levels of vitamin B-12 were more likely to have depression or anxiety. A 2018 study found that people who ate foods high in B vitamins — in this case, yeast based spreads such as Marmite and Vegemite — had better anxiety and stress scores than people who did not. This was more pronounced for spreads fortified with vitamin B-12. Earlier studies have also revealed that a more rapid progression of PD symptoms occurred in those with lower B12 levels than those with higher levels. This raises the possibility that prevention or early correction of low B12 status may slow the onset of disability in PD.