Vitamin B12 deficiencies are more often caused by other disorders that impair absorption of the vitamin. Others include overgrowth of bacteria in the intestine, tropical sprue, and overexposure to nitrous oxide. Many drugs can impair the ability to absorb vitamin B12 but rarely cause a deficiency. Vitamin B12 deficiency from diet is very rare and usually does not occur even in alcoholism, strict vegetarianism, or in malnourished people with kidney failure or cancer. Causes of Folate Deficiency.
Poor diet coupled with alcoholism is the most common cause of folate deficiency.
The body stores only about 100 times its daily requirements for the vitamin and can exhaust this supply within about three months if the diet is deficient in folate. Alcohol abuse not only contributes to malnutrition, but alcohol causes chemical changes that can result in lower folate levels. Any condition that disturbs the small intestine and impairs its absorption ability, including inflammatory bowel disease, sprue, parasitic diseases such as giardiasis, and short bowel syndrome, can cause a deficiency. Deficiencies can also be caused by high demand for folic acid caused by conditions such as cancer, pregnancy, severe psoriasis, severe hyperthyroidism, and hemolytic anemia. Some drugs, including dilantin, methotrexate, trimethoprim, and triamterene, may also hinder folate absorption.