What are vitamin B12 and folate deficiencies?

Vitamin B12, Also known as: Cobalamin; Folic Acid
What are vitamin B12 and folate deficiencies?
B12 and folate are B complex vitamins that are necessary for normal red blood cell formation, tissue and cellular repair, and DNA synthesis. A B12 and/or folate deficiency reflects a chronic shortage of one or both of these vitamins. Since the body stores 3 to 6 years worth of B12 and about a 3 months’ supply of folate in the liver, deficiencies and their associated symptoms can take months to years to manifest in adults. Infants and children will show signs of deficiency more rapidly because they have not yet established extensive reserves.
Over time, a deficiency in either B12 or folate can lead to macrocytic anemia, a condition characterized by the production of fewer but larger red blood cells, thus a decreased ability to carry oxygen. Due to the anemia, those affected may be weak, light-headed, and short of breath. A deficiency in Vitamin B12 can also result in varying degrees of neuropathy or nerve damage that can cause tingling and numbness in the person’s hands and feet. In severe cases, mental changes that range from confusion and irritability to dementia may occur.
Pregnant women need increased amounts of folate for proper fetal development.  Because of the added stress of rapidly growing cells (the fetus), increased amounts of folate are required. If a woman has a folate deficiency prior to pregnancy, it will be intensified during gestation and may lead to premature birth and neural tube birth defects, such as spina bifida, in the child. The number of neural tube defect cases decreased by 36% in the U.S. since focusing on folate supplements during pregnancy. Restless leg syndrome during pregnancy is another neurologic symptom associated with decreased folate.

Symptoms
The symptoms associated with B12 and folate deficiency are initially subtle and nonspecific. They are related to the resulting macrocytic anemia, nerve involvement, and gastrointestinal changes. People with an early deficiency may be diagnosed before they experience any overt symptoms. Other affected people may experience a variety of mild to severe symptoms that can include:
Diarrhea
Dizziness
Fatigue, weakness
Loss of appetite
Malabsorption
Paleness
Rapid heart rate
Shortness of breath
Sore tongue and mouth
Tingling, numbness, and/or burning in the feet, hands, arms, and legs (with B12)
Confusion
Paranoia
Causes
There are a variety of causes of B12 and/or folate deficiencies. They include:
Insufficient dietary intake
B12 is found in animal products such as red meat, fish, poultry, milk, and eggs. Folate (also called folic acid) is found in leafy green vegetables, citrus fruits, dry beans, yeast, and fortified cereals. The human body stores several years’ worth of B12(68-19-9) in the liver. Since it is readily available in the food supply, a dietary deficiency of this vitamin is extremely rare in the U.S. It may be seen sometimes with general malnutrition, in vegans (those who do not consume any animal products, including milk and eggs), and breastfed infants of vegans. Deficiencies in children and infants show up fairly quickly since they do not have the stores seen in adults.
Folate deficiency used to be a common, but in 1997 the US government mandated supplementation of cereals, breads, and other grain products with folic acid. Since this implementation, the number of women of child-bearing age with decreased folate levels was reduced from 21% to less than 1%. Because folate is stored in tissue in smaller quantities than B12, folate must be consumed more regularly than Vitamin B12.
Malabsorption
Both B12 and folate deficiencies may be seen with conditions that interfere with absorption in the small intestine. These may include:
Celiac disease
Bacterial overgrowth or the presence of parasites in the intestines
Reduced stomach acid production; stomach acid is necessary to separate B12 from the protein in food. This is the most common cause of B12 deficiency in the elderly and in individuals on drugs that suppress gastric acid production.
Pernicious anemia, the most common cause of B12 deficiency. Intrinsic factor (IF) is a protein made by parietal cells that line the stomach. B12 binds to intrinsic factor, forming a complex that is absorbed in the intestines. With pernicious anemia, little or no intrinsic factor is produced, thus preventing the absorption of B12.
Surgery that removes part of the stomach (and the parietal cells) or the intestines may greatly decrease absorption, a concern that is considered when gastric by-pass procedures are performed.
Chronic pancreatitis
Increased need
All pregnant women need increased amounts of folate for proper fetal development. If a woman has a folate deficiency prior to pregnancy, it will be intensified during gestation and may lead to premature birth and neural tube defects in the child. People with cancer that has spread (metastasized) or with a chronic hemolytic anemia such as sickle cell have an increased need for folate.
Other causes:
Chronic alcoholism can cause B12 and/or folate deficiency due to poor intake and impaired release of B12 from dietary proteins.
Some drugs can cause B12 deficiency, for example, metformin and omeprazole, which cause B12 malabsorption and impaired release of B12 from food proteins due to decrease in gastric acids, respectively.
Anti-seizure medications such as phenytoin can decrease folate as can drugs such as methotrexate, which blocks folate absorption and affect body metabolism and utilization of folate, respectively.
Treatment
Treatment for B12 and folate deficiencies frequently involves long-term or lifetime supplementation. People who lack intrinsic factor or have conditions causing general malabsorption require injections of B12. Folate/folic acid is an oral supplement.
Doctors recommend that all women contemplating having a child take folic acid supplements prior to and during pregnancy to ensure that they have a sufficient store for normal fetal development.
If a person is deficient in both B12 and folate, he will require replenishment of both. If someone with a B12 deficiency only takes folic acid supplements, the macrocytic anemia may be resolved but the underlying neuropathy caused by the B12 deficiency will persist. Appropriate treatment should resolve symptoms but may not reverse all of the nerve damage.