A condition characterized by subnormal levels of HEMOGLOBIN, the oxygen-binding PROTEIN in blood. Half a million Americans are at risk for anemia, including 40 percent of pregnant women, pre-menopausal women, vegans (those who eat no animal products), adolescents relying on JUNK FOOD diets, infants, and children with inadequate diets.Anemia may result from either an inadequate number of RED BLOOD CELLS (erythrocytes) or an abnormally low hemoglobin content of red blood cells. With deficient functional red blood cells, the oxygen supply to tissues is inadequate for optimal RESPIRATION, causing shortness of breath, FATIGUE, weakness, pallor, headache, and lowered resistance to infection. There are two general types of anemia based on red blood cell size. Megaloblastic anemia is characterized by large red blood cells; their shortened life span results in a decreased number of cells. Microcytic anemia is characterized by small red blood cells with reduced hemoglobin content. Many nutritional deficiencies lead to anemia. Inadequate dietary IRON, COPPER, FOLIC ACID, PROTEIN,
VITAMIN B6, vitamin B12, VITAMIN C, VITAMIN A, VITAMIN E, and RIBOFLAVIN can cause this condition. Each of these nutrients is required for the production of red blood cells (ERYTHROPOIESIS). Iron deficiency anemia is the most common diet-related anemia in the United States and it represents the last stage of iron deficiency. It is characterized by small, pale red blood cells (microcytic anemia), due to chronic blood loss or inadequate iron intake. Symptoms include FATIGUE, pallor, and shortness of breath. Studies of the nutritional status of developed nations have routinely found up to 30 percent of a population with iron deficiency. Groups that are at highest risk are children under the age of two years, teenage women, pregnant women, and the elderly. Pregnancy drastically increases the requirement of iron. In terms of blood loss the most common causes of iron deficiency are excessive bleeding during menstruation and intestinal bleeding due to parasites, ulcers, or malignancy. Iron deficiency can be caused by impaired iron uptake by the intestine, due to a lack of stomach acid (ACHLORHYDRIA) or from chronic DIARRHEA. With iron deficiency, the resulting anemia can be treated by iron supplementation.
Deficiencies of either folacin or vitamin B12 can cause anemia because each is essential for DNA synthesis and deficiencies impair erythrocyte production. Folic acid deficiency is much more common because folic acid stores in the body are small, yet folic acid participates in many biosynthetic reactions. On the other hand, vitamin B12 is stored in the LIVER, and only trace amounts are required daily for a few specific functions. Anemia due to inadequate folic acid and vitamin B12 produces large (macrocytic) cells with a short life span. This form of anemia can occur when intake of fresh vegetables is very limited, or when the need for folic acid outstrips intake, as may occur during pregnancy or in ALCOHOLISM. Treatment with folic acid can ameliorate megaloblastic anemia, yet mask an underlying vitamin B12 deficiency. This point emphasizes that treatment of anemia requires expert medical supervision.
Anemia can also indicate a serious condition unrelated to diet. Non-nutritional causes of anemia include chronic blood loss and congenital defects in red blood cell formation, such as thalassemia or sickle cell anemia, due to mutant hemoglobins, and spherocytosis (spherical red blood cells). Hemolytic anemia is the result of excessive hemolysis (destruction of red blood cells) in susceptible people exposed to bacterial toxins, toxic chemicals, or drugs that may produce JAUNDICE.
Anemia also may result from reduced nutrient uptake due to the presence of parasites and chronic infections, gastrointestinal disease or bowel resection
An extreme reaction of the immune system in response to exposure to foreign substances. Insect bites, drugs, injected serum, and certain foods can create anaphylaxis. This abnormal response or immediate hypersensitivity is usually very rapid in susceptible individuals who may have been sensitized by previous exposure, and may produce shock (“anaphylactic shock”). The massive release of histamines and other inflammatory agents leads to spasming of smooth muscles, especially those of the air passageways, and to widespread swelling due to the increased water leaking out of capillaries. Symptoms range from asthma to fever, itching, hives, and flushed skin in mild cases, to chest constriction, irregular pulse, painful, labored breathing, and convulsions in severe cases. Anaphylaxis can be life-threatening and may require emergency room care.
Cellular processes that do not require oxygen. Energy can be produced in cells without oxygen. Anaerobic GLYCOLYSIS refers to an energy yielding process by which ATP, the energy currency of the cell, is produced from GLUCOSE without the participation of oxygen. As an example, skeletal muscle produces LACTIC ACID and ATP from glucose when oxygen supplied to muscle is inadequate to meet energy needs during strenuous physical exertion.
Processes involved in synthesizing the molecules needed for cellular growth and maintenance. Thus the formation of PROTEIN, DNA, RNA, LIPID, CARBOHYDRATE, FAT, and GLYCOGEN are anabolic processes. Anabolism consumes chemical energy in the form of ATP and NADPH (a reducing agent), which are supplied by CATABOLISM, the energy-yielding oxidative processes involved in degradation. Optimal function and health rely upon a balance of anabolic and catabolic processes (homeostasis). These two branches of metabolism are controlled by the ENDOCRINE SYSTEM, which in turn responds to external influences such as diet. Anabolic processes require small building blocks supplied by breaking down STARCH, PROTEIN, and FAT in foods to build larger molecules. GLYCEROL and FATTY ACIDS are the subunits of fat; AMINO ACIDS yield proteins; and glucose yields glycogen. Fat and carbohydrate degradation provides an energized form of ACETIC ACID (acetyl CoA) to synthesize fatty acids and cholesterol. Other specialized products are also assembled from several different types of smaller precursors. For example, heme, the iron-containing pigment of the oxygen transport protein HEMOGLOBIN, is synthesized from an amino acid (GLYCINE) and SUCCINIC ACID, a common intermediate in energy-producing pathways.
A water-soluble form of STARCH found in seeds, tubers, and root vegetables. It is made up of long chains of GLUCOSE units, and often contains a thousand or more glucose units. Amylose differs from the other prevalent form of starch, AMYLOPECTIN, which is highly branched. Amylose forms large spiral configurations when dissolved in water and can react with iodide to form a characteristic blue-purple pigment. Amylopectin and amylose occur together in starch, and the relative amounts vary depending on the plant sources. During digestion, AMYLASE breaks down amylose to maltose, a disaccharide composed of two glucose units. An intestinal enzyme, MALTASE, then hydrolyzes maltose to the simple sugar glucose, the ultimate product of starch digestion.
The water-insoluble form of STARCH. Plants synthesize this very long chain of GLUCOSE units as a storage form of energy, often to nurture the future embryo, seedling or sprout. It is often the major form of starch and it possesses a highly branched, bushy structure resembling liver GLYCOGEN (animal starch). In contrast, AMYLOSE is made up of single straight chains of glucose units.