Deficiencies in vitamin B12 and folate (vitamin B9) is linked with higher homocysteine levels in blood, which could be associated with a greater physical fatigue in men and decreased motivation in women, according to a study. "This suggested relationship between vitamin B12, folate, and fatigue in healthy individuals may represent the first report of its kind. Blood homocysteine levels have traditionally raised concerns in relation to cardiovascular disease, dementia, and fractures," lead researcher Hiroaki Kanouchi, from Osaka Metropolitan University in Japan, said.