A number of prospective studies have suggested that elevated serum total homocysteine (tHcy), and low folate and vitamin B12 levels are a risk factor for Alzheimer’s disease (Clarke et al. Arch Neurol 1998; 55: 1449-1455). In the Prospective Population Study of Women in Gothenburg, elevated tHcy in midlife was associated with a hazard ratio of 2.1 for developing AD and 2.4 for AD with no cerebrovascular disease (Zylberstein et al. Neurobiol Aging 2011; 32: 380-386). B vitamins (folate, B6, B12) are cofactors or substrates for enzymes in homocysteine metabolism.