Vitamin B12 Deficiency : Vegetarians, elderly may not get enough vitamin B12, says the Harvard Health Letter

These days, most health warnings about vitamins focus on the danger of overdose. For vitamin B12, though, it's more likely that people are getting too little. In fact, B12 deficiency is the most common nutritional deficiency in the developing world and possibly in the United States as well, reports the August issue of the Harvard Health Letter.

Sometimes the only symptoms of a B12 deficiency are subtle cognitive and neurological changes. More serious shortages can result in dementia or anemia. Breast-fed infants of mothers with a B12 deficiency are at risk for severe developmental abnormalities and irreversible neurological damage.