vitamin deficiency; elderly; old age; B1; B2; B3; B4; B5; B6; B7; B9; B12; thiamine; riboflavin; oxidative damage; niacin; mitochondria; choline; alzheimer's disease; pantothenic acid; longevity; pyridoxamine; glycation; folic acid; stroke; neurodegenerative disease; cobalamin; depression