An Overview Of Common Causes Of Anemia
Anemia occurs when the concentration of the pigment
hemoglobin in red blood cells falls below normal. Hemoglobin is
essential for delivering oxygen from the lungs to the body tissues.
Iron deficiency is the most common cause of anemia. Although iron
deficiency is generally the most common cause of anemia, there are
other nutritional, genetic, and environmental causes as well.
Iron was one of the first substances identified as essential in the
human diet. The physiologic function of iron in hemoglobin and its
role in anemia was determined over a two hundred year period from the
1680's.
By World Health Organization criteria, anemia is considered to
exist when the non-pregnant adult female has a haemoglobin level below
11 grams per 100 milliliter of venous blood.
Iron deficiency anaemia refers to anemia that results from iron
deficiency or impaired iron status. Iron dependent physiologic
functions can become impaired before anaemia develops. Although iron
deficiency anemia can occur in all socioeconomic groups, it has
historically been most common among the poor as is still the case today.
Because the synthesis of blood cells requires many cellular and
metabolic processes, a deficiency of any nutrient essential to
hemoglobin production produces adverse effects on these processes.
Good nutrition is fundamental to adequate red blood cell production.
Nutritional anaemia may be due to a dietary deficiency of iron, folate,
vitamin B12, protein, and other vitamins and minerals. Other causes of
anemia include the inherited or acquired inability to use nutrients
required for haemoglobin production.
Nutritional anaemia should be distinguished from deficiencies per se
of iron, folate, or vitamin B12, because an individual may have
manifest any one of these deficiencies without being anaemic. In iron
deficiency disorders immune function and behaviour are not directly
attributable to the anaemia. Similarly, the impaired nerve function of
vitamin B12 deficiency occurs independently of anemia.
The bioavailability of iron is determined by the nature of the diet
and by regulatory mechanisms in the digestion that reflect the body's
physiologic need for iron. Two types of iron are present in food, heme
iron and nonheme iron.
Most of the iron in the diet is present as nonheme iron and consists
primarily of iron salts. The amount finally absorbed is influenced by
other constituents of the diet that either enhance or inhibit, by
decreasing solubility and the absorption of iron.
Iron absorption tends to be poor from meals in which whole grain
products and legumes predominate, but the addition of even small
amounts of foods containing vitamin C (ascorbic acid) substantially
increase the absorption of iron from the entire meal. On the other
hand, tea and coffee, decrease the absorption of nonheme iron.
Heme iron comes from the hemoglobin in meat, poultry, and fish. The
body absorbs a greater percentage of heme iron, and its absorption is
less affected by other dietary constituents.
Iron deficiency causes a substantial reduction in work capacity and
mild anemia can decrease performance in exercise. The major
consequence of this muscle impairment is a lessened capacity for
prolonged exercise or physical endurance. An impaired capacity to
maintain body temperature in a cold environment is another
characteristic of iron deficiency anemia.
Changes in behaviour and impaired intellectual performance may
result from iron deficiency. Even mild iron deficiency significantly
decreases responsiveness, activity, and attentiveness, and increases
body tension, fearfulness and a tendency to fatigue.
Iron deficiency and folate deficiency are more common in women
because of two forms of metabolic stress peculiar to women; the monthly
blood loss in premenopausal women and the drain on maternal nutrient
stores imposed by pregnancy. The fetus will take from the mother
whatever it needs in order to be normal at birth, even if this produces
severe nutrient deficiency in the mother. Nevertheless, a women who has
sufficient iron stores to provide for her increase in hemoglobin mass
during pregnancy, and who breast-feeds for six months will have her
iron needs covered by adequate intake of dietary iron.
Iron deficiency can be prevented by increasing dietary intake,
improving bioavailability from the diet, or decreasing body losses of
iron. Dietary intakes can be improved by increasing the consumption of
iron-rich foods, administering iron supplements, and fortifying certain
food products with iron. Fortification of cereal and grain products is
a relatively inexpensive and effective means of increasing iron intake.
The absorption of iron from fortified cereals can be increased
threefold if the cereals are also fortified with about 5 mg of vitamin
C per mg of iron.
Prevention of nutrition-related anaemia depends on adequate dietary
intake of iron, vitamin B12, and folate as well as the full complement
of other essential nutrients. Folate deficiency anemia usually occurs
among women late in the course of pregnancy, among small premature
infants, and among alcoholics. Strict vegetarians who consume no foods
of animal origin, especially women who are pregnant or nursing, should
take supplemental sources of vitamin B12.
Supplementation has the disadvantage of requiring extra effort and
expense compared with fortified foods. Its effectiveness for a given
individual requires evaluation by a qualified health professional. Iron
supplement use and recommendations to increase dietary intake are
usually not necessary for the general population.
An additional concern is that increased iron intake can harm
individuals who are susceptible to iron overload. Abnormal amounts of
tissue iron accumulate over the years as a result of a genetic defect
in absorption, eventually damaging the liver, heart, pancreas, and
adrenal glands. Excessive iron intake may affect the absorption of
other trace elements.
Food Labels: Evidence related to the role of iron and folate
in anemia suggests that food labels should indicate the content of
these nutrients.
Food Programs: Because groups that benefit from food programs
are those at highest risk for anemia, such programs should continue to
be made available to high-risk groups and should encourage consumption
of foods rich in iron and folate. The current levels of iron
fortification are safe and adequate, and no changes should be
recommended at this time.
Anemia occurs when the concentration of the pigment
hemoglobin in red blood cells falls below normal. Hemoglobin is
essential for delivering oxygen from the lungs to the body tissues.
Iron deficiency is the most common cause of anemia. Although iron
deficiency is generally the most common cause of anemia, there are
other nutritional, genetic, and environmental causes as well.
Iron was one of the first substances identified as essential in the
human diet. The physiologic function of iron in hemoglobin and its
role in anemia was determined over a two hundred year period from the
1680's.
By World Health Organization criteria, anemia is considered to
exist when the non-pregnant adult female has a haemoglobin level below
11 grams per 100 milliliter of venous blood.
Iron deficiency anaemia refers to anemia that results from iron
deficiency or impaired iron status. Iron dependent physiologic
functions can become impaired before anaemia develops. Although iron
deficiency anemia can occur in all socioeconomic groups, it has
historically been most common among the poor as is still the case today.
Causes of Anemia
Because the synthesis of blood cells requires many cellular and
metabolic processes, a deficiency of any nutrient essential to
hemoglobin production produces adverse effects on these processes.
Good nutrition is fundamental to adequate red blood cell production.
Nutritional anaemia may be due to a dietary deficiency of iron, folate,
vitamin B12, protein, and other vitamins and minerals. Other causes of
anemia include the inherited or acquired inability to use nutrients
required for haemoglobin production.
Nutritional anaemia should be distinguished from deficiencies per se
of iron, folate, or vitamin B12, because an individual may have
manifest any one of these deficiencies without being anaemic. In iron
deficiency disorders immune function and behaviour are not directly
attributable to the anaemia. Similarly, the impaired nerve function of
vitamin B12 deficiency occurs independently of anemia.
The bioavailability of iron is determined by the nature of the diet
and by regulatory mechanisms in the digestion that reflect the body's
physiologic need for iron. Two types of iron are present in food, heme
iron and nonheme iron.
Most of the iron in the diet is present as nonheme iron and consists
primarily of iron salts. The amount finally absorbed is influenced by
other constituents of the diet that either enhance or inhibit, by
decreasing solubility and the absorption of iron.
Iron absorption tends to be poor from meals in which whole grain
products and legumes predominate, but the addition of even small
amounts of foods containing vitamin C (ascorbic acid) substantially
increase the absorption of iron from the entire meal. On the other
hand, tea and coffee, decrease the absorption of nonheme iron.
Heme iron comes from the hemoglobin in meat, poultry, and fish. The
body absorbs a greater percentage of heme iron, and its absorption is
less affected by other dietary constituents.
Iron deficiency causes a substantial reduction in work capacity and
mild anemia can decrease performance in exercise. The major
consequence of this muscle impairment is a lessened capacity for
prolonged exercise or physical endurance. An impaired capacity to
maintain body temperature in a cold environment is another
characteristic of iron deficiency anemia.
Changes in behaviour and impaired intellectual performance may
result from iron deficiency. Even mild iron deficiency significantly
decreases responsiveness, activity, and attentiveness, and increases
body tension, fearfulness and a tendency to fatigue.
Iron deficiency and folate deficiency are more common in women
because of two forms of metabolic stress peculiar to women; the monthly
blood loss in premenopausal women and the drain on maternal nutrient
stores imposed by pregnancy. The fetus will take from the mother
whatever it needs in order to be normal at birth, even if this produces
severe nutrient deficiency in the mother. Nevertheless, a women who has
sufficient iron stores to provide for her increase in hemoglobin mass
during pregnancy, and who breast-feeds for six months will have her
iron needs covered by adequate intake of dietary iron.
Iron deficiency can be prevented by increasing dietary intake,
improving bioavailability from the diet, or decreasing body losses of
iron. Dietary intakes can be improved by increasing the consumption of
iron-rich foods, administering iron supplements, and fortifying certain
food products with iron. Fortification of cereal and grain products is
a relatively inexpensive and effective means of increasing iron intake.
The absorption of iron from fortified cereals can be increased
threefold if the cereals are also fortified with about 5 mg of vitamin
C per mg of iron.
Prevention of nutrition-related anaemia depends on adequate dietary
intake of iron, vitamin B12, and folate as well as the full complement
of other essential nutrients. Folate deficiency anemia usually occurs
among women late in the course of pregnancy, among small premature
infants, and among alcoholics. Strict vegetarians who consume no foods
of animal origin, especially women who are pregnant or nursing, should
take supplemental sources of vitamin B12.
Supplementation has the disadvantage of requiring extra effort and
expense compared with fortified foods. Its effectiveness for a given
individual requires evaluation by a qualified health professional. Iron
supplement use and recommendations to increase dietary intake are
usually not necessary for the general population.
An additional concern is that increased iron intake can harm
individuals who are susceptible to iron overload. Abnormal amounts of
tissue iron accumulate over the years as a result of a genetic defect
in absorption, eventually damaging the liver, heart, pancreas, and
adrenal glands. Excessive iron intake may affect the absorption of
other trace elements.
Nutrition Programs and Services
Food Labels: Evidence related to the role of iron and folate
in anemia suggests that food labels should indicate the content of
these nutrients.
Food Programs: Because groups that benefit from food programs
are those at highest risk for anemia, such programs should continue to
be made available to high-risk groups and should encourage consumption
of foods rich in iron and folate. The current levels of iron
fortification are safe and adequate, and no changes should be
recommended at this time.
- The Surgeon General's Report on Nutrition & Health, 1988
No comments:
Post a Comment