Humans require vitamin B12 to help produce red blood cells, maintain healthy nerves, and trigger the production of substances necessary to make the genetic material in cells known as DNA, or deoxyribose nucleic acid. In most cases, people in the United States ingest enough vitamin B12 through natural food sources and fortified foods, such as breakfast cereals, according to the National Institutes of Health Office of Dietary Supplements. In addition, because the body can store several years' supply of vitamin B12, deficiency rarely occurs, according to the Mayo Clinic. Medical conditions that interfere with the absorption of vitamins increase the risk of developing a deficiency.
Symptoms
Patients suffering from a deficiency in vitamin B12 experience a variety of symptoms. Without enough vitamin B12 the body cannot produce enough red blood cells, a condition known as anemia. Symptoms of anemia include fatigue and weakness that can lead to constipation, loss of appetite and weight loss. Vitamin B12 deficiency can cause damage to the nerves causing numbness and tingling in the hands and feet. Other symptoms include difficulty with balance, depression, confusion, dementia, memory impairments and mouth soreness, as listed by the National Institutes of Health Office of Dietary Supplements.
Associated Conditions
Medical conditions that affect the digestive tract can interfere with the absorption of nutrients. The most common condition associated with B12 deficiency, pernicious anemia, occurs when the body destroys the parietal cells in the stomach that make intrinsic factor. In order to absorb vitamin B12, it must first bind to intrinsic factor. Without enough intrinsic factor, the body cannot absorb B12. Other conditions that can interfere with the absorption of vitamin B12 include chronic alcoholism, Crohn's disease and celiac disease, according to MedLine Plus.
Effects of Aging
Approximately 10 to 30 percent of older adults suffer from atrophic gastritis, a digestive condition characterized by a decrease in hydrochloric acid levels. When ingesting natural sources of vitamin B12, such as meat, eggs and dairy products, the hydrochloric acid in the stomach must first separate the protein from the vitamin before it can bind to intrinsic factor and be absorbed. A decrease in hydrochloric acid production decreases the absorption of vitamin B12 and increases the risk of deficiency.
Vegetarians
Animal products provide the only natural sources of vitamin B12. Those who follow a strict vegetarian diet, especially vegans who fail to consume any type of animal product, have an increased risk of developing vitamin B12 deficiency.
Pregnancy Effect
Because vitamin B12 crosses the placenta to a baby, pregnant women use and require more vitamin B12. Lactating women excrete vitamin B12 into the milk, which helps infants get enough vitamin B12. Because of the increased needs of pregnant and breastfeeding women the risk of developing a B12 deficiency increases.
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