Vitamin B12 is essential to the healthy functioning of the nervous system and helps the body make DNA and RNA. It is also important for the development and maintenance of normal red blood cells and the production of neurotransmitters, explains Dr. Andrew Weil.
People who are deficient in vitamin B12 often experience a number of symptoms, including tiredness, weakness, dizziness, shortness of breath and palpitations, notes Dr. Weil. Numbness, bleeding gums, mouth sores and digestive upsets, such as nausea and diarrhea, also sometimes occur. However, because vitamin B12 is present in a wide variety of foods and people store it in their livers, vitamin B12 deficiency is rare, states Mayo Clinic.
Strict vegetarians and vegans sometimes develop vitamin B12 deficiency due to a lack of dietary protein, according to Dr.Weil. Pregnant women, the elderly and people who cannot absorb vitamin B12 from their intestinal tracts are also at risk. Drinking large amounts of alcohol or taking certain medicines, such as stomach acid-blocking agents or antibiotics, increases the likelihood of developing a vitamin B12 deficiency.
Most people need only small amounts of vitamin B12 to maintain good health. The recommended dietary allowance for people over the age of 14 is 2.4 micrograms, explains the National Institutes of Health Office of Dietary Supplements. Pregnant women and women who are breastfeeding need 2.5 micrograms and 2.8 micrograms per day respectively. Fish, shellfish, meats, poultry, dairy products, eggs and fortified cereals are sources of vitamin B12.