Vitamin B-6 and vitamin B-12 play important roles in the production of red blood cells. Insufficient intake or absorption of these B vitamins can lead to vitamin deficiency anemia, a condition characterized by fatigue, weakness, shortness of breath and difficulty concentrating. The body absorbs vitamin B-6 easily, but many factors can limit the absorption of vitamin B-12.
B-12 Absorption Process
Vitamin B-12 absorption relies on several substances in the stomach. Naturally occurring vitamin B-12 in foods remains attached to protein. Before the body can absorb the vitamin, hydrochloric acid and gastric protease in the stomach must separate it from the protein. The free vitamin B-12 must then attach to the glycoprotein intrinsic factor in the stomach. The gastrointestinal tract then absorbs the vitamin. Synthetic vitamin B-12 from fortified foods and supplements is not attached to protein and, therefore, does not require hydrochloric acid for absorption.
Factors Hindering B-12 Absorption
Several health conditions can hinder the absorption of vitamin B-12 from foods and supplements. Atrophic gastritis and gastrointestinal surgeries can decrease the amount of hydrochloric acid in the stomach, hindering the absorption of natural vitamin B-12 from foods. Pernicious anemia causes a lack of intrinsic factor, hindering the absorption of natural and synthetic vitamin B-12. Crohn's disease and celiac disease can also cause chronic malabsorption of vitamin B-12 and other nutrients. Doctors often treat B-12 absorption problems with intramuscular injections.
B-12 Absorption in Healthy Adults
The capacity of intrinsic factor limits absorption of vitamin B-12 even in healthy adults. Healthy adults absorb only 56 percent of a 1 microgram oral dose of vitamin B-12, and an even smaller percentage of larger doses, according to the National Institutes of Health Office of Dietary Supplements. A healthy adult typically absorbs only 10 micrograms of a 500 microgram oral supplement, or about 2 percent.
B-6 Absorption
Because the body absorbs vitamin B-6 easily and vitamin B-6 occurs naturally in a variety of plant and animal-based foods, vitamin B-6 deficiency occurs very rarely in the United States, notes the National Institutes of Health Office of Dietary Supplements. Poor diets may cause vitamin B-6 deficiency in older adults, however, and alcoholics may also be more vulnerable to vitamin B-6 deficiency because excessive alcohol consumption can destroy vitamin B-6 in the body.
Member Comments