Stress, aging, active lifestyles, poor digestion, alcohol consumption, PMS, menopause, and cardiovascular disease are just some of the factors that increase the body 's need for B vitamins and why so many people can benefit from supplements. Inadequate intake of some B vitamins is not uncommon and deficiencies can be associated with fatigue, insomnia, depression, and migraines. In the diet, B vitamins are found in yeast, green leafy vegetables, and lentils. The best sources of B12 are meat and seafood, making supplements particularly advisable for vegetarians.