What are vitamin B12 and folate deficiencies?
Vitamin B12 and folate deficiencies are a lack of these two B complex vitamins that the body needs for several important functions. They are required to make normal red blood cells (RBCs), repair tissues and cells, synthesize DNA (the genetic material in cells). B12 is also important for normal nerve cell function. B12 and folate (also known as folic acid or vitamin B9) are nutrients that cannot be produced in the body and must be supplied by the diet. The body stores 3 to 6 years worth of B12 and about a 3 months' supply of folate in the liver. So a B12 and/or folate deficiency reflects a chronic shortage of one or both of these vitamins.
In the U.S., B12 and folate deficiencies are not common in healthy adults because the body can store sufficient amounts and most adults eat enough foods or take supplements that contain these vitamins to meet their daily requirements. There are, however, people at risk of deficiency, such as the elderly, people with intestinal problems that prevent them from absorbing enough of the vitamins, heavy alcohol drinkers, and pregnant women, who need increased amounts of these vitamins.
B12 and folate deficiencies and their associated signs and 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 had time to store sufficient amounts.
Over time, a deficiency in either B12 or folate can lead to macrocytic anemia, a condition in which red blood cells are enlarged. This production of fewer but larger red blood cells decreases the blood's ability to carry oxygen. People with anemia may be weak, light-headed, and short of breath. Megaloblastic anemia, a type of macrocytic anemia, is characterized by the production of fewer but larger RBCs in addition to some cellular changes in the bone marrow. Other laboratory findings associated with megaloblastic anemia include decreased white blood cell (WBC) count and platelet count.
A deficiency in 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 folate for proper fetal development because of the added stress of rapidly growing fetal cells. A folate deficiency during pregnancy, especially in the early weeks when a woman might not know she is pregnant, may lead to premature birth and neural tube birth defects (NTDs) such as spina bifida in the child. To help prevent NTDs, the Food and Drug Administration mandated increased folate supplementation of grain products a number of years ago, which led to about a 50% decrease in neural tube defects in the U.S. Even so, it can be difficult sometimes to get enough folate from foods, so it is recommended that all women who may become pregnant take 400 micrograms of folate every day.