Nutritional Deficiences and Anemia
Poor nutrition may contribute to inadequate red blood cell production — especially deficiencies in iron and certain types of vitamin B. When an increased production of red blood cells (RBCs) is necessary — such as during pregnancy or after an episode of bleeding — these nutrients are even more critical. Iron and vitamin B supplements are often prescribed to prevent anemia.
Iron deficiency is the most common cause of anemia in the United States. It occurs when the body either has depleted all iron stores or is unable to use the iron available to make adequate amounts of hemoglobin (the protein in the RBC which carries oxygen). For Americans, however, lack of dietary iron is rarely the sole cause of this anemia. Usually, people have blood loss as well. Young women are at particular risk, because of monthly blood loss with menstruation. Up to 10 percent of women in their reproductive years have iron deficiency, and, in about half of those cases, it is severe enough to cause anemia. Pregnant women also are at risk, which is why prenatal vitamins containing extra iron are recommended during pregnancy.
Iron-deficiency anemia is less common in men and in postmenopausal women in the United States. Low iron levels in these groups is a warning that abnormal bleeding could be occurring due to undiagnosed medical conditions such as ulcer disease or colon cancer.
The highest amounts of iron are found in meat, spinach, raisins, lentils and enriched flour. Iron is absorbed most efficiently, however, from red meat — which is why pre-menopausal women who don't eat much meat are at particular risk for iron-deficiency anemia. Other factors also contribute to how much iron is absorbed in the body. Vitamin C enhances the absorption of iron from the intestine, so if you combine foods with iron and vitamin C, you will increase the amount of iron absorbed. Citrus fruits are well-known for their vitamin C content, but many vegetables are also a good source of vitamin C, such as tomatoes, cauliflower, broccoli and potatoes.
Folic acid (folate) deficiency
A lack of folic acid — one of the B-complex vitamins — may cause another kind of anemia. Folic acid is critical to the body's metabolism of amino acids, as well as to the formation of healthy red blood cells. In folic-acid deficiency, the RBCs produced are unusually large and have a shortened life span. Folic acid is a water-soluble vitamin and thus cannot be stored in any great quantity in the body. Therefore, it must be replenished by diet on a regular basis; the body will exhaust its supply of folate in about three months if the diet is deficient. Folic-acid deficiency may occur among older people and heavy alcohol drinkers because they are at risk of eating a poor diet. There also is an increased demand for folate during pregnancy, and in medical conditions that cause rapid RBC destruction, such as sickle cell anemia and certain cancers. In these cases, folate supplements usually are prescribed. In addition, adequate folic acid intake is necessary for women who may become pregnant to help prevent birth defects.
Folate is found in liver, fortified cereals, lentils, beans, green leafy vegetables such as spinach, collards, asparagus, and broccoli, orange juice, and in products made from folate-fortified flour. As with iron, not all of the folic acid you eat is absorbed by your body. The amount absorbed depends on the type of food and the method of cooking it. It's important to avoid overcooking vegetables, and avoid leaving them out at room temperature for an extended period of time; this can significantly decrease folic-acid concentrations.
Vitamin B12 deficiency
Vitamin B12 deficiency, like folate deficiency, causes anemia — unusually large RBCs are produced with a shortened life span. Older Americans may have B12 blood levels that are below the optimal range even when there is no anemia. This usually is due to an inability to absorb vitamin B12, rather than a dietary deficiency, although strict vegetarians are at risk, because vitamin B12 is found only in animal products.
Another cause of vitamin B12 deficiency is pernicious anemia, an autoimmune disease in which the immune system attacks stomach cells, decreasing the amount of a protein called intrinsic factor. This protein is essential to the absorption of vitamin B12 from food. Vitamin B12 deficiency also can develop as a complication of gastrointestinal surgery and certain diseases of the intestine, preventing adequate absorption.
Good sources of vitamin B12 include liver, tuna, cottage cheese, yogurt and eggs. Most standard multivitamin supplements also provide the recommended daily allowance of vitamin B12.