Our bloodstream carries oxygen from our lungs to every cell in our body, and it carries carbon dioxide back to the lungs for release into the air. It transports the nutrients used for fuel and those necessary for the growth and repair of tissues. In addition, it carries the waste products of tissue metabolism to be excreted by the kidney. Furthermore, our blood is a reservoir of cells to fight infection either by carrying immune substances or by engulfing invading organisms. For these functions, the blood has evolved into a very special tissue containing several constituent parts, each of which is highly adapted.
There are two types of cells in the bloodstream: red cells and white cells. The white cells protect us against infection. The red cells (erythrocytes) carry oxygen and carbon dioxide. They give the blood its color. Either quantitative or qualitative changes in these cells will cause anemia.
An erythrocyte is a very special cell highly adapted for its job as a carrier of oxygen and carbon dioxide. In its mature form, the cell circulates through the blood as a small sphere filled with hemoglobin. Hemoglobin is a large molecule made of two kinds of subunits: heme, a small iron-containing ring-like structure, and globin, a large chain-like protein molecule. The hemoglobin carries both the oxygen and the carbon dioxide. The more hemoglobin, the more seats available on the oxygen-carrying train; the less hemoglobin, the fewer seats. When the amount of it drops below a certain level, the person is anemic. Simply stated, anemia means having too little hemoglobin.
To carry out its special functions, the red cell sacrifices certain properties that are present in all other cells. During its development, it loses its nucleus (the part of all cells that is responsible for maintaining many of the cell’s life processes). Consequently, the red cell has a much shorter life than any other cells. Its average life span is 120 days. About 8 percent of our red cells die every day and must be replaced.
These cells are replaced in the bone marrow, where cells that contain nuclei divide rapidly and constantly increase in number. Some of these cells undergo a maturation process during which they will synthesize hemoglobin, and lose their nuclei. They become mature erythrocytes, which are released into the bloodstream to replace those that were lost. The bone marrow constantly produces new cells and releases them to the blood as they are needed.
Because red cells are constantly lost and replaced, it is easy to understand how anemia can develop. If they are lost faster than they can be replaced, the amount of hemoglobin circulating in the blood will drop. We will become anemic. Such an imbalance between the rate of cell loss and the rate of replacement can occur either because the cells are withdrawn from the bloodstream too rapidly or because they are released from the bone marrow too slowly.
Both of these situations happen, and either has important nutritional implications. Perhaps the most obvious loss of red cells (and the hemoglobin they contain) occurs when we bleed. When the bleeding is mild, the bone marrow is able to compensate by speeding up the production of red cells and rapidly releasing them into the bloodstream. This will prevent the hemoglobin levels from falling. When the bleeding is severe, even if the bone marrow is working at capacity, it is unable to replace the lost cells fast enough. Anemia will ensue. Therefore, whether we become anemic following blood loss depends on how well our bone marrow can supply new erythrocytes. This ability to respond depends, in part, on our nutritional status.
As we have seen, new red cells are constantly manufactured in the bone marrow. The immature red cells must divide rapidly, and new hemoglobin must be synthesized within the maturing cells. Both of these processes depend on the availability of certain nutrients. Three nutrients essential for cell division are: folic acid, vitamin B-12, and zinc. Iron is crucial for the synthesis of hemoglobin. A deficiency in folic acid, vitamin B-12, or zinc will cause a reduced rate of cell division within the bone marrow and result in the production of fewer red cells. A deficiency of iron will result in a reduced synthesis of hemoglobin within the maturing red cell. Thus, the most common forms of nutritional anemia are caused by inadequate supplies of iron, folic acid, vitamin B-12, and zinc to the bone marrow. Our diet is the ultimate source of these nutrients.
Iron is so important to the body that specific mechanisms have evolved for its conservation. Iron is an integral part of hemoglobin, and most of the iron in our bodies is present in this form. Every type of cell contains small amounts as part of the enzyme systems necessary for cell respiration. Finally, iron is present in muscle cells in a molecule known as myoglobin, which is important in voluntary muscle function. It is also stored in the liver, spleen, intestines, and to some extent in other organs.
Almost all the iron from tissues, including that released by dying red cells, is carried in the blood to storage sites for withdrawal when needed. Thus, under normal conditions when no blood is lost from the body, very little is excreted; almost all is revitalized. Even an injury to the tissues, such as in a bruise, releases iron that the body can reuse.
Dietary iron requirements for an adult male are small. Therefore, deficiency of this element in adult males is rare. When it does occur, it usually signals bleeding from an unseen site. This is a serious symptom that requires immediate medical attention. By contrast, iron deficiency is quite common in both sexes during the human growth period and is usually due to inadequate intake. The volume of blood must grow. Hence, red cells are constantly added over and above those that are lost. More hemoglobin is synthesized, and more iron is required. An infant’s blood volume can double during the first year of life. The one-year-old has twice the number of total red cells and, hence, twice as much body iron, as the newborn. If an adequate supply is not available, iron deficiency, and (possibly) anemia, will occur. Adolescence is another period of very rapid growth when the total number of red cells must increase and iron deficiency may develop.
During her reproductive life, the adult woman is also at risk for iron deficiency. She regularly loses blood through menstruation. Again, if her intake of dietary iron is inadequate to meet the demands imposed by this constant iron loss, she will develop an iron deficiency and, eventually, the anemia that accompanies this condition. Anemia is the last stage of iron deficiency. It occurs only after the iron stores within the body have been exhausted. For this reason, even a mild anemia due to iron deficiency should not be ignored. It means all our stores have been exhausted and we are not consuming enough iron to keep our hemoglobin level high enough for optimal body function.
A woman is particularly at risk for iron deficiency during pregnancy. Her blood volume expands, hence more red cells must be manufactured to meet this expansion. In addition, the fetus is growing and developing. Part of that growth is the establishment and rapid expansion of its own blood supply. This requires iron, which must come from the mother—either from her diet or from her iron stores. The more pregnancies a woman has undergone, the greater her risk for iron deficiency, both during later pregnancies and between them. Pregnancy places such a demand on iron requirements that supplements are routinely prescribed for pregnant women.
Iron deficiency is a progressive that begins with a slow depletion of iron stores and proceeds to mild, then moderate, and, finally, severe anemia. The rate at which anemia develops depends partly on the existing level of stores and on the difference between the amount of iron lost and the amount in the diet. Let us suppose that a woman has iron stores of 1,000 mg, she consumes 10 mg per day of usable iron, and she loses 15 mg per day (this includes menstrual losses prorated on a daily basis). She is losing 5 mg per day more than she is absorbing. In 200 days her entire reserves will be used up. Anemia will begin to develop. Even a loss of 1 mg per day more than her body absorbs will result in a depletion of her entire iron reserves in less than three years. If she donates blood, has an accident that involves blood loss, or suffers a nosebleed, these losses must be factored into the equation. For a woman to prevent iron deficiency, she must absorb as much iron as she is using. If her reserves are low, then she needs to restore them by absorbing more than she is using, i.e., by being in a state of positive iron balance.
Iron is supplied by variety of foods. Therefore, it is reasonable to ask why anyone should be in negative iron balance. There are two reasons. First, the body will absorb only a small fraction of the iron in our food. How much depends on a number of factors: the kind of food, the other components of the diet, and the state of our iron reserves. Second, the lifestyle of “modern” American women reduces the amount of iron in their diets.
Iron is absorbed by an active process. First, it is converted by hydrochloric acid in the stomach into a form that can be absorbed. When it reaches the small intestine, it is carried into the surface cells by ferritin (a specialized protein). This binds the iron and pulls it into the cells of the intestinal wall, where it is either deposited as storage iron or released into the bloodstream. While in the bloodstream, the iron is bound to transferrin, another carrier protein, which circulates in the plasma. The amount of iron absorbed depends on the nature of the iron-containing food, the other components of our diet, and the state of our iron reserves. The state of our iron reserves is the most important factor determining how much iron we will absorb. When our reserves are low, absorption is high. When they are high, absorption is lower.
Iron in our food has two forms: heme iron, from hemoglobin, and non-heme iron. Heme iron occurs primarily in meat, fish, and egg yolks. Nonheme iron is found in plant sources. About 15 to 20 percent of the heme iron in our diet will be absorbed. By contrast, we absorb only about 5 percent of nonheme iron. Only about 10 percent of dietary iron in the mixed American diet is used. For any individual, however, the amount of absorption will vary. If you are a vegetarian, you will absorb less than 10 percent; if you eat much meat, more than 10 percent.
Regardless of the source of dietary iron, its absorption is influenced by other components of the diet. Vitamin C consumed at the same meal will increase iron absorption. Thus, the orange juice we drink at breakfast will increase the iron we absorb from eggs or fortified cereal. By contrast, certain components of cereal grains known as phytates interfere with iron absorption. This is not a problem in the usual American diet because our major grain sources (wheat, corn, and rice) are not rich in phytates. The phytate they contain in their original state is almost entirely removed in processing. In some countries, such as Egypt and other Middle Eastern countries, staple grains are high in phytates, and the absorption of iron and other minerals can be diminished.
The nature of the signal by which our bodies regulate iron absorption is not known. Depending on how much is already present, somehow, a signal is sent to the cells lining the small intestine to hold back or speed up the process. This internal system affords a very important protection against both deficiency and overload. When iron is abundant, the body will absorb only what it needs. Unfortunately, for a variety of reasons, iron may not be abundantly available. If it is not, the body cannot make up the deficit. Table 22 shows the iron content of a variety of foods.
Table 22. Iron Content of Foods
.3-7 mg/serving Carrots 1 cup
Fruit: e.g., apples, Collards 1 cup
bananas Potato 1 med
melons, 1.5-2 mg/serving
citrus, Barley ½ cup
pineapple, Buckwheat ½ cup
etc. 1 avg. size Oatmeal 1 cup
Corn grits 1 cup Chicken 3 4 oz
Popcorn Bologna 3 4 oz
(popped) 1 cup Ham 2 oz
Bread (any) 1 slice Dried apricot
enriched halves 6 large
Macaroni, Green beans 1 cup
spaghetti, or Brewers’ yeast1 tbsp.
noodles ½ cup
Peanut butter 2 tbsp. 2-4 mg/serving
Mushrooms 1/3 cup Amaranth 3 ½ oz
Eggplant ½ cup Figs, dried 3 med.
Tomato 1 small Cooked peas &
beans ½ cup
. 7-1.4 mg/serving Blackstrap
Rice, cooked molasses 1 tbsp.
(brown or Tofu (soy
white curd) 4 oz.
enriched) 1 cup
Tortilla (6 in. 4-5 mg/serving
diameter) 1 Beef (lean only)
Cream of Wheat1 cup all cuts 3 oz.
Wheatena 2/3 cup Lamb (lean only)
Wheat germ 1 tbsp. all cuts 4 oz.
Dry bulgur wheat 2 tbsp. Calf’s liver 1 oz.
Pumpkin seeds 1 2 tbs. Raisins ½ cup
Berries (all) 1 cup
Broccoli 1 cup
Low calorie diets restrict our food intake, thereby limiting the amount of iron available. On a 1,200-calorie diet, a woman would have to eat liver twice a week to meet her iron requirement. Below 1,200 calories, it becomes almost impossible for her to get enough iron from food alone. Therefore, a woman who is constantly dieting is at increased risk for iron deficiency. The lower her caloric intake, the greater that risk.
Consuming large amounts of alcohol will interfere with iron absorption. A woman who is a moderately heavy drinker and limits her caloric intake is in double jeopardy. Since many American women routinely practice calorie control while consuming moderate amounts of alcohol, iron deficiency is common in this population.
Folic acid is another nutrient essential for prevention of anemia. This vitamin, a member of the “B-complex,” is essential for normal cell division. The more rapid the rate of multiplication, the higher the requirement for folic acid. The bone marrow cells divide more rapidly than cells located elsewhere in the body. A deficiency of this vitamin will manifest itself primarily by reducing the rate of cell division in the bone marrow. When this rate decreases sufficiently to compromise the marrow’s capacity to replace lost red cells, their number in the blood falls. Anemia results. The faster these cells have to be replaced, the greater the need for folic acid. Women replace their red cells quicker than men. Women must constantly make up for the blood losses of menstruation. Thus, women require more folic acid than men. Anemia due to folic acid deficiency is more common in adult women than in adult men. The heavier a woman’s menstrual losses, the greater her need for folic acid.
Folic acid deficiency is the most common vitamin shortage in the United States (see Table 23 for foods rich in folic acid). This problem has become so evident that inclusion of this vitamin in bread, cereals, “enriched” flour, white rice and other refined grain products is now required by government regulations. The level of enrichment will be the amount necessary to replace the portion lost in the milling process. White bread will now have as much folic acid as the whole-grain product currently provides (about 27 micrograms per slice). It has long been a common practice for manufacturers to fortify breakfast cereals with folic acid. “Fortified” cereals contain as much as 100 micrograms of folic acid per normal serving. The Recommended Daily Intake is 400 micrograms for adult men and women.
Table 23. Folic Acid Content of Foods in Micrograms
5-20 mcg/serving 20-50 mcg/serving
Carrot 1 med. Green beans 1 cup
Ear of corn 1 med. Cucumber 1 sm.
Mushrooms 3 large Squash 2/3 cup
Potato 1 med. Strawberries 1 cup
Apple 1 med. Egg 1 lg.
Hard cheese 1 oz. Kidney 3 oz.
Grapefruit ½ med. Shellfish 6 oz.
Milk 8 oz. Yogurt 8 oz.
Bread 1 slice Wheat germ 2 tbs.
Sesame seeds 1 tbs. Orange 1 med.
Lean beef, veal,
or pork 6 oz.
100-150 mcg/serving 200-300 mcg/serving
Avocado (med.)6 oz. Brewer’s yeast1 tbs.
Breakfast cereals Spinach 4 oz.
(fortified) 1 oz. (dry)
Lentils, cooked ½ cup
Liver (all) 3 oz.
Broccoli 2 stalks
Orange juice 6 oz.
Unlike iron, folic acid cannot be stored to an appreciable extent, and the requirement increases during periods of great demand for new red cells. Hence, adequate quantities must be consumed daily. Also unlike iron, almost all the folic acid in our diet is absorbed. The excess is simply excreted in the urine. Because our body has no control over how much folic acid is absorbed, constant calorie control limits the amount of folic acid available from our diet more so than it limits the amount of iron. It cannot extract a higher portion of this nutrient from our food when our reserves are low. Thus, if we are anemic because of folic acid deficiency, our body cannot protect itself by absorbing a greater amount of this nutrient.
Even moderate consumption of alcohol will reduce the amount we absorb, and certain prescription drugs can affect availability of folic acid. Perhaps the most important one, in this respect, is the contraceptive pill. It may both decrease absorption and increase excretion of folic acid. Women who use oral contraceptives are at increased risk for folic acid deficiency. This problem is compounded when women stop taking oral contraceptives to become pregnant. If they succeed, and particularly if they succeed quickly, they may enter the early stages of pregnancy deficient in the vitamin. Because pregnancy is accompanied by rapid cell division in the developing fetus, and because both maternal and fetal bone marrows are very active in making new cells, a woman’s folic acid requirement increases dramatically. A deficiency during early pregnancy may be associated with certain types of congenital malformations. Later in pregnancy, a deficiency may lead to anemia in the mother. Therefore, it is recommended that every pregnant woman take folic acid supplements, particularly if she has been on oral contraceptives for a long time. She should begin the supplementation as soon as she discontinues the pill.
Since the conditions necessary for the development of iron-deficiency anemia and folic-acid-deficiency anemia are often similar, some women can become anemic because they lack both nutrients. It is important to diagnose such a condition. Treatment with iron or folic acid alone will not cure this anemia. Fortunately, by examining a drop of your blood, your physician will be able to tell if you have a combined form. As we shall see, this is only one of many reasons self-treatment of anemia is not advisable. Treatment of a combined anemia is simple—supplementation with both iron and folic acid. Prevention of a recurrence may involve changes in lifestyle, in addition to changes in diet.
Vitamin B-12 is another important nutrient in the prevention of anemia. The type of anemia associated with a deficit of it is identical to the anemia that results from folic acid deficiency. Vitamin B-12 is necessary for folic acid to work. In essence, a person who has a vitamin B-12 deficiency also lacks folic acid, not because the latter is missing in the diet, but because the body cannot properly use it. Vitamin B-12 is found in all foods of animal origin. Hence, excepting in pure vegetarians, dietary vitamin B-12 deficiency almost never occurs. Vitamin B-12 is the only water-soluble vitamin that is stored in the body. Nutritional anemia resulting from a diet deficient in vitamin B-12 is very rare. It takes about three years for our normal reserves to be depleted. Hence, anemia caused by a vitamin B-12 deficiency takes a long time to develop. Unless there is some abnormality (such as the body’s inability to absorb the vitamin), the condition should occur only in pure vegetarians; or, because an “intrinsic factor” in the stomach is required for absorption of the vitamin, in persons that have had surgical removal of most of the stomach.
The mineral zinc is also necessary for cell division. Thus, the demand for zinc will increase when the bone marrow is very active and during pregnancy when cell division increases in both the mother and the fetus. Zinc usually occurs in the same foods as iron. Hence, people who are iron deficient may be zinc deficient. Like iron, zinc is stored in the body, and there is some evidence that the state of our zinc reserves influences the rate at which our bodies absorb this mineral from food. Unlike iron, zinc is not a structural element in hemoglobin or any other major blood protein. Blood loss is not accompanied by the loss of large quantities of zinc. However, the response of the bone marrow to blood loss increases the zinc requirement. Thus, women of childbearing age need increased zinc because more red cells have to be made.
As with the other nutrients involved in nutritional anemias, zinc deficiency will result when the increased demand is not met by the diet. The quantity and quality of the food consumed limit the amount in the diet. Again, limiting calories results in an increased risk for zinc deficiency. If the diet is low in foods with significant zinc content that risk is compounded (See Table 24 for foods rich in zinc).
Table 24. Zinc Content of Foods in Milligrams
0.2-0.5 mg/serving: 0.5-1 mg/serving:
Egg 1 med. Puffed wheat 1 oz.
Gefilte fish 3½ oz. Cheddar cheese 1 oz.
Mango ½ med. Tuna 3 oz.
Applesauce ½ cup White rice 1 cup
Pineapple juice 8 oz. White bread 2 slices
Tomato 1 med. Cranberry apple
Potato, cooked 1 med. drink 8 oz.
Chicken breast 3 oz.
1-1.5 mg/serving: Milk 8 oz.
Clams 3 oz.
Brown rice 1 cup 4-5 mg/serving:
Brown rice 1 cup Beef (lean) 3½ oz.
Wh. wheat bread 2 slices Pork (lean) 3½ oz.
Popcorn 2 cups Lamb (lean) 3½ oz.
Wheat germ 1 tbs. Liver 3 oz
Bran ¾ cup
Other: 9.4 mg—Pacific oysters (raw) 3 ½ oz.
74.7 mg—Atlantic oysters (raw) 3 ½ oz.
Even if your body is deficient in zinc, you are not likely to become anemic for lack of it. There are two reasons. First, it takes a greater degree of depletion to cause anemia from zinc deficiency than it does from an iron or a folic acid deficiency. Second, zinc deficiency will manifest itself in other ways before anemia occurs. A person with iron-deficiency anemia will often be zinc deficient as well (because the same foods tend to supply both nutrients). The anemia, however, will be caused by the lack of iron, not the lack of zinc. Even a moderate iron deficiency often rapidly results in anemia. Therefore, iron-deficiency anemia should be treated by increasing your consumption of iron-rich foods (in addition to iron supplements). These foods will incidentally supply enough zinc to replenish your supply of this mineral, and you will establish an eating pattern that may prevent later deficiencies.
Even if you are not anemic, your zinc reserves may be low enough to cause skin problems, taste abnormalities, endocrine problems, and (in children) diminished growth and several maturation problems. Because zinc deficiency is associated with congenital malformations of the fetus, this is particularly important for women of childbearing age. These malformations occur at low serum-zinc levels when other signs of deficiency are absent. Because zinc deficiency is so prevalent in women who are iron deficient, any pregnant woman who is iron deficient should also use zinc supplements. Another consideration is that alcohol reduces zinc absorption and therefore increases our risk for deficiency.
Lack of other nutrients in the diet can cause anemia; but this happens at a very low frequency. Shortages of copper and vitamin E have been implicated. However, the deficits must be prolonged and severe before the symptoms appear. Only people with unorthodox eating habits are at risk for anemia due to lack of copper and vitamin E.
Anemia resulting from a combination of other nutrient deficiencies is quite rare. Occasionally a woman who is a pure vegetarian (vegan) may develop an anemia caused by a lack of both iron and vitamin B-12. This happens because the best source of iron is meat and other animal products, and vitamin B-12 is found only in animals and animal products. However, even small amounts of meat, fish, or dairy foods will satisfy our vitamin B-12 requirement. Therefore, the vegan who is anemic is most likely iron deficient, and only rarely deficient in vitamin B-12.
The signs and symptoms of nutritional anemia are similar, regardless of the type. They result from the same abnormality, too little hemoglobin in the blood. Hemoglobin is red in color, which is reflected in the body, particularly where the blood comes close to the surface, such as the nail beds, the tips of the fingers and toes, the earlobes, and the skin around the eyes. Anyone who is anemic will display a lightening of color in these areas—usually ranging from pink to a grayish-white. As the anemia progresses, a general pallor develops, regardless of our skin color. One way to test for anemia is to press on our nail beds until they become white, and then release the pressure. A prompt return to pink is the normal response. Anemia must be suspected if the pink returns very slowly.
Hemoglobin carries oxygen from the lungs to the tissues. Not enough oxygen reaches the tissues when insufficient hemoglobin is present. Certain signs and symptoms will develop. Tiredness and general fatigue are among the earliest signs. Our attention span becomes shorter and we begin to do poorly at our job, particularly if we work at something that requires concentration. We become listless and irritable. We lose patience, and the least bit of exertion bothers us. Finally, we can become weak and short of breath. All these symptoms are nonspecific; that is, they can occur with conditions other than anemia. The condition is easily diagnosed by blood tests that reveal the low hemoglobin levels.
Anemia may be a result of causes other than faulty nutrition. Therefore, it is essential that a physician identify the cause. Sometimes it may be a sign of a very serious disease. For example, certain diseases of the blood or bone marrow will produce anemia. The marrow may “break down” and not be able to replace the red cells that are constantly lost. No kind of nutritional treatment will cure this kind of anemia. Sometimes the red cells themselves break down much more rapidly than normal. This condition may be due to genetic abnormalities in the red cells, as in sickle-cell anemia, or to certain toxins that cause red cell damage.
Bleeding is the most common non-nutritional cause of anemia. The blood loss may be slow and not easily recognized; for example, bleeding from the gastrointestinal tract. Unlike the anemias mentioned above, that caused by bleeding will respond to nutritional treatment. The anemic condition is due to iron deficiency—not because of insufficient iron in your diet, but because we are abnormally draining our iron stores. Iron supplementation will cure the anemia but not the condition that caused anemia—a very important principle. If it is iron-deficiency anemia, why are you iron deficient? In women it is usually because their iron intake is not sufficient to meet their normal demands, or because of heavy menstrual periods, or one or more pregnancies that may have drained their iron reserves.
Iron deficiency rarely occurs in men because of too little iron in their diet. An adult male’s normal requirement is small. Iron-deficiency anemia in an adult male must be considered a sign of abnormal bleeding; thus, the cause of the bleeding must be established. Self-treatment with iron may temporarily correct the symptoms of iron deficiency, but this delays the diagnosis of the problem and may seriously jeopardize our health.
Anyone who is anemic should see a physician to determine the cause. In a woman who has no other physical problems, the physician may prescribe an iron supplement and recommend a diet high in iron. For a man, a much more extensive series of diagnostic tests may be necessary to determine the cause of iron loss.
The populations mainly at risk for nutritional anemias are women during the childbearing years and children of both sexes during their growing years. In addition, there is some evidence that certain elderly men and women may be at increased risk. Unlike the case of most of the other diseases we have discussed, your race or your family history is not important in determining your risk. There are no known genetic factors that increase a person’s chances of developing nutritional anemias. Similarly, other factors such as smoking, high blood pressure, obesity, and lack of exercise—so important in many of the diseases already discussed—do not influence our risk for developing a nutritionally induced anemia. However, for the population groups mentioned above, there are certain other risk factors that can increase their chances of developing nutritional anemia.
During the childbearing years, women go through certain cyclic changes in their physiology that put them at increased risk for nutritional anemias. Primary among these physiologic states are menstruation, pregnancy, and lactation—each requiring specific nutrients. In addition, during this childbearing period, many women have certain lifestyle practices that increase their risk for nutritional anemias. The use of the contraceptive pill increases the need for folic acid; and some diets reduce the availability of iron, zinc, and folic acid. Excess use of alcohol reduces the absorption of the same three nutrients. This combination of life cycle and lifestyles places the adult woman at greater risk for nutritional anemias than the adult man. The extent of that risk depends on how these factors interact. It is important for any woman to establish her own risk for developing anemia. That can be accomplished more precisely with this condition than with any of the other diseases we have discussed.
How heavy are your menstrual periods? This is perhaps the most important question you have to answer. Some women have very light menstrual periods and lose only small amounts of iron. They require only small increases in dietary zinc and folic acid to replace the lost red cells. Other women lose copious amounts of blood with each period and must constantly renew their iron reserves and supply their bone marrow with enough zinc and folic acid. Most women fall somewhere in between.
Naturally, menstruation stops during pregnancy. However, the needs for your blood volume to expand, and for the fetus to establish its own new blood supply, more than balance this temporary stage. Your bone marrow works much faster during pregnancy; therefore, zinc and folic acid deficiencies are more common at this time. Hundreds of thousands of new red cells are pouring into your bloodstream from your bone marrow and into the circulation of the fetus from its bone marrow. Each of these cells contains hemoglobin and its iron. All the iron must come from the mother—from her reserves, from her diet, or from both. During pregnancy a woman is more apt to develop anemia than when she is between pregnancies. Equally important, pregnancy can drain her reserves of iron and place her at greater risk for anemia afterward. The more pregnancies you have undergone, the greater your risk for nutritional anemia, particularly if you did not take iron and folic acid supplements during those pregnancies.
If you have had twins or triplets, your risk is increased both during and after pregnancy. Considerable blood can be lost at delivery. For this reason, your physician will determine your hemoglobin and red-blood-cell count shortly after the baby is born. If these values are low, you will probably be given an iron supplement. However, even if they are normal, your nutrient reserves may have been drained. Remember that anemia is the last stage of iron deficiency. It occurs only after all your iron stores have been depleted. In summation, your risk for nutritional anemia is increased after pregnancy, and the more pregnancies you have undergone, the greater your risk.
Nursing your baby will not increase your risk for nutritional anemia to the extent that menstruation or pregnancy does. Your requirements for iron, zinc, and folic acid will increase; but so will your appetite. The increased food should go a long way toward supplying enough of these nutrients. Nursing women often do not resume menstruating until after the infant is weaned. Blood loss will be minimal; therefore, the nursing period is a good time to replace the nutrient stores lost during pregnancy.
Although oral contraceptives have been shown to decrease the absorption of a number of vitamins, including folic acid and vitamin B-12, these drugs alone will rarely cause nutritional anemia. However, if a woman is already at high risk, using oral contraceptives may result in the anemia of folic acid deficiency. For some women, on the other hand, oral contraceptives reduce the severity of menstrual periods, in which case the risk for anemia is reduced.
Perhaps the greatest lifestyle factor influencing your risk for nutritional anemia is a reducing diet. As you lower your calorie intake, you decrease your opportunity for getting your daily requirement of iron, zinc, and folic acid. Below 1,000 calories per day, it is almost impossible for a woman to get her iron requirement from food alone. If you are continually dieting, your risk for anemia is increased. This is particularly true if the reducing diet is unbalanced. Remember that meat is the best source of iron and zinc, and certain vegetables are the best source of folic acid.
Increasing numbers of American women are practicing some form of vegetarianism. A potential problem in this practice is the increased risk of iron-deficiency anemia. Since meat is the best source of iron, a woman who eats little or no meat is at increased risk for iron deficiency. She should manage her diet to provide a maximum source of vegetable iron. If eggs are part of her diet, the yolks are an excellent source of iron.
Alcohol, consumed in even moderate amounts, can increase our risk for nutritional anemia, in two ways. First, it provides calories that are totally devoid of all other nutrients, thus cutting down the total number of nutrient-carrying calories. For example, suppose you are limiting yourself to 2,000 calories. If your diet is varied, it will furnish your daily requirement of iron, zinc, and folic acid. But if you consume 500 calories from alcohol (less than five ounces per day), this leaves only 1,500 calories worth of food to provide your entire daily requirement. This is much more difficult to achieve.
Second, alcohol directly impairs the absorption of iron, zinc, and folic acid. This reduces the amount your body gets from your food. There is less food to supply the nutrient, and poorer absorption from the food you do consume. Alcohol, even moderate amounts, must be weighed as a risk for nutritional anemia.
Both genders are at risk during the growth period of life. As our body grows, so does the volume of our blood; and the faster we grow the more our blood volume expands. To keep pace with the expanding blood volume, the bone marrow must supply red cells faster. More zinc and folic acid are required. Additional iron is required for these new red cells to mature and enter the bloodstream. Thus, the risk for anemia increases during any period of rapid growth. During fetal life, the mother is supplying the nutrients required for the formation of fetal blood; so the infant is rarely anemic. However, the first year of life is a period of special risk. This is particularly true if the fetus is born prematurely. For the first few months of life, the infant will consume breast milk or infant formula as its sole source of nutrition. Breast milk contains iron in a highly absorbable form, and folic acid is abundant in her breast milk (provided the mother’s diet is well-balanced.)
Human breast milk also contains sufficient amounts of zinc. Thus, the breast-fed infant will rarely develop nutritional anemia. If the baby is bottle-fed, an infant formula that simulates breast milk and is fortified with iron is advisable. When the infant is four months old, solid foods may be introduced. However, breast milk or infant formula should still be used until the infant is nearly one year old. Solid foods should emphasize the nutrients needed to prevent nutritional anemia, with the emphasis on iron. Many infant cereals are fortified with iron. Meat products, and some strained green vegetables, are also rich sources of iron. If the infant is a girl, preventing anemia is not enough. It is important also to ensure that her iron reserves are adequate. Otherwise, she will start out in life with a disadvantage.
The preschool years and the early school years are times when growth proceeds at a moderate rate. Therefore, iron, zinc, and folic acid requirements will be somewhat increased. But these years are also a time of major physical activity and hence increased food intake. Rarely is supplementation necessary unless the child is not receiving adequate amounts of a varied diet. If the family is strictly vegetarian, then the child could be iron deficient; and fortified foods or an iron supplement may be warranted.
Adolescence is another time of rapid growth when nutritional anemias are common in both genders. Because of their greater increase in growth rate, adolescent boys develop anemia more often than girls. However, the problem is more serious in girls. The adolescent girl with a nutritional anemia enters adulthood with exhausted reserves, particularly those of iron. Hence, her body is unable to meet the increased demands of menstruation and, later, of pregnancy. By contrast, the adolescent boy will be much more able to make up a deficit as he stops growing (when his demand for iron, zinc, and folic acid drops).
Therefore, both genders have the potential for developing nutritional anemias during adolescence. Children of either sex who are at risk because of their very rapid growth, coupled with diets marginal in iron, zinc, or folic acid, should take preventive precautions. This is particularly true if they have any other risk factors. For example, the adolescent who is constantly dieting is at increased risk; the vegetarian adolescent is at increased risk; and the adolescent who drinks alcohol is also at increased risk. Particularly at risk is the adolescent girl who becomes pregnant. She is growing, her blood volume is expanding because she is pregnant, and her fetus is manufacturing new blood. The nutrients necessary to meet these demands may not be available even if her diet is good. Therefore, any adolescent who is pregnant should receive supplements of iron, zinc, and folic acid.
There is some evidence that older men and women may be more prone to nutritional anemias than young adults. The reasons are not entirely clear. Iron must be converted into its proper form for digestion by the hydrochloric acid in the stomach. Older people have less stomach acidity, and hence proper conversion may not take place. Thus, the iron in their food may not be absorbed sufficiently to meet their needs. Again, in older people there is evidence that the production the intrinsic factor necessary for the absorption of vitamin B-12 is reduced. Thus, an elder person, particularly one who does not eat much meat or meat products may develop anemia due to vitamin B-12 deficiency. The evidence for folic acid deficiency is inconclusive. Some studies show that a high proportion of senior citizens are deficient in this vitamin; others do not. Perhaps the biggest problem with determining whether aging is a factor in nutritional anemias is that many older people suffer from chronic diseases of all sorts. Some of these diseases may themselves increase the possibilities for developing anemia. Thus, in any older person anemia per se may be due not to dietary factors but to an accompanying disease. It is therefore important for any elderly individual who is even mildly anemic to have the cause of that anemia determined by a physician.
Any infant whose birth weight was low and who is growing rapidly would automatically be at high risk. Any infant who was of low birth weight and who suffers an episode of bleeding would be at high risk. Even an infant whose birth weight was adequate but who is growing very rapidly and fed a formula that contained no iron would also be at high risk.
Since you do not know ahead of time whether your infant will grow rapidly or have nosebleeds or experience other forms of blood loss, it would be prudent to take certain precautions to prevent nutritional anemias in your infant. These precautions are simple: Breast-feed your child if you can. If you cannot breast-feed, use an infant formula that contains iron. When you introduce solid foods (at around four months), choose those that are rich in iron, folic acid, and zinc.
To score the risk factors for infants, consider:
- Birth weight. Infants who weighed five and a half pounds or less at birth are at increased risk for nutritional anemias. Score 3 if your child falls into this category.
- Specific problems at birth. Any infant who has had an “Rh problem” or any other condition necessitating a blood transfusion is at very high risk—score 5.
- Very rapid growth during the first year of life. If birth weight has more than doubled at four months or more than tripled at ten months, score 2.
- Bleeding during childhood. Severe nosebleeds, blood loss due to lacerations, and major surgical operations all increase risk. Score 2 for each.
- Use of any infant formula that does not contain iron, and is the sole or major form of nutrition—score 3.
During childhood and adolescence, both genders are equally at risk for nutritional anemias. Pertaining to this stage of development:
- If you were at risk as a child (see above) and did not take preventive measures, your risk as an adolescent increases—score 3.
- If your growth rate is very rapid (more than three inches during any year), your risk increases—score 3.
- If you have had any episodes of significant bleeding before or during adolescence, your risk is higher—score 2 to 4 (depending on the severity of the bleeding).
- If you are a vegetarian, your risk is increased—score 2.
- If you begin your menstrual periods early (before age twelve)—score 3.
- If you are on a reducing diet, score 3. If your diet is unbalanced and low in iron, zinc, or folic acid—add 2 more points.
- If you are a “regular” user of alcohol, score 2; if you are a heavy drinker—score 3.
- If you become pregnant—score 5.
A score of 5 or above places an adolescent at high risk. Thus, a person who was at risk as a child, and who undergoes very rapid adolescent growth, is at high risk without any of the other factors being present. A rapidly growing adolescent who becomes a strict vegetarian or decides to go on a reducing diet is also at high risk and should take steps to prevent nutritional anemias. Of course, any adolescent who becomes pregnant is immediately at high risk and should be taking iron, zinc, and folic acid supplements.
Pertaining to women during the childbearing years, use the following list: (A score of 5 or more places you in the high-risk category.)
- A history of high risk during infancy and/or adolescence—score 3.
- Heavy menstrual period—score 3.
- Menstrual periods remaining heavy for more than three days—score 2.
- Lasting more than four days—score 3.
- Previous pregnancies (including miscarriages and induced abortions)—score 1 for each. Score 2 for each pregnancy resulting in twins.
- Bleeding complications at delivery—score 2.
- Other significant bleeding episodes—score 3.
- Frequent dieting to control weight—score 3.
- A pure vegetarian (vegan) diet—score 2.
- Use of oral contraceptives—score 2.
- Regular frequent consumption of alcohol—score 2.
- Heavy alcohol consumption—score 3.
As you can see, your previous history is very important. If you were at risk as a child or adolescent and did not take preventive measures, any of the other factors mentioned above automatically puts you into a high-risk category.
We use two main principles in constructing a diet to protect against the development of nutritional anemias. First, the foods must be of high nutrient density for iron, zinc, and folic acid. The nutrient density relates to the quantity of these nutrients per calorie in the daily diet. It should be as high as possible. Thus, a low-calorie food that is only moderately high in iron may be better than a high-calorie food that is very high in iron. Second, certain foods are very rich in these nutrients either naturally or because they are fortified. Emphasis should be put on incorporating some of these foods into your regular diet.
To achieve the first objective, you need not only to eat certain foods but also to eliminate (or at least markedly reduce) others. Any food that supplies calories without these nutrients should be de-emphasized. For example, alcohol and refined sugar have no nutrients, only calories. Therefore, a moderate reduction in these two “foods” can allow you to eat more nutrient-dense food without increasing your caloric intake. Fat, while carrying certain vitamins and supplying essential fatty acids, does not contain any of the nutrients that are important in protecting you against anemia. Hence your intake of fat, the most calorie-dense of all the nutrients (9 calories per gram), should be lowered substantially.
First, calculate roughly how many calories you are taking in (or wish to, if you are planning to lose weight). Then calculate how many calories you can eliminate by reducing alcohol, sugar, and fat consumption. Finally, decide what foods you will eat to increase your intake of iron, zinc, and folic acid to protect against anemia. In some cases, as we will see, you will not be able to do this without eating fortified foods or taking supplements.
How much iron, zinc, and folic acid are necessary to prevent anemia? If you are not anemic yet, you should take in more iron than you are losing and enough zinc and folic acid to allow your bone marrow to work at maximum efficiency. Supplying more than this amount of zinc and folic acid will have little or no extra benefit. Therefore, any score over 5 would indicate that you should try to supply about one and a half to two times the recommended daily intake. This amount should be more than adequate to meet your needs and allow your bone marrow to do its job. An adult woman’s zinc requirement is 12 mg (15 mg during pregnancy); hence, 20 mg per day is more than adequate. Similarly, 1 mg (two and a half times the adult female requirement) of folic acid is adequate.
With iron, however, the situation is quite different. If you replace only the amount you are losing, you will avoid iron-deficiency anemia, but since your reserves are depleted, you will remain at risk for this anemia. To lower your risk, you must rebuild iron stores by taking in more iron than you are losing. How much more depends on how depleted you were initially. Your physician can determine this, but it requires certain complicated tests. A less accurate but adequate method is to use your risk score to determine how much you need to take in. The higher the score, the more depleted you are. A score between 5 and 10 should allow iron rebuilding with slightly more than the recommended daily requirement (18 mg), about 20 to 25 mg. For a person with a score between 10 and 20, 30 mg of iron daily would be reasonable.
If your score is above 20, you should attempt to ingest 40 mg of iron per day. This last figure cannot be met from food alone unless you are consuming large numbers of calories and large quantities of iron-rich foods. A person with that high a score should be taking an iron supplement. Even 30 mg per day (in food alone) would be difficult for a woman, particularly if she is concerned about her calories. The use of iron-fortified foods is one option. If you choose a fortified food containing 100 percent of the recommended daily intake (15 mg for women) then you need only 15 mg from the rest of your diet. Try to get that amount from meat sources—red meats (lean cuts), liver, and egg yolks—since that type of iron is better absorbed. If you do not wish to consume fortified foods, an iron supplement of 20 to 30 mg is needed. If your score is between 5 and 10, you can get the iron you need from your diet, if you choose foods carefully, avoid nutrient-poor foods, and consume adequate calories. If you are on a reducing diet, you should take an iron supplement. If you are a vegetarian and your score is 5 or above, you should take an iron supplement or eat iron-fortified foods.
The following chart may be useful.
Table 25. Iron Requirement to Prevent Anemia
Score Requirement Source
5-10 20-25 mg/day diet, if calories are adequate
0-20 30 mg/day diet plus fortified foods or supplement
21-30 40 mg/day diet plus supplement
In planning a diet to prevent anemia, first, decide how much iron you need. Then decide if you need supplementation. If so, choose a supplement at an appropriate dosage (usually 20 to 30 mg per day). If you select fortified foods, pick one (usually a cereal) that contains 100 percent of the RDI for iron (15 mg); it may be fortified with zinc and folic acid as well.
Decide how many total calories you wish to take in each day (between 1,800 and 2,300 for the average woman; up to 2,800 for a very active woman). Decrease foods of low nutrient density (alcohol, refined sugar, fat). From the Tables we have provided, you can pick foods that are high in iron, zinc, and folic acid. Select generously to reach the amount you need. It may sound difficult to do, but it isn’t. Suppose you need about 25 mg per day of iron. You have the option of eating a fortified cereal several times per week, liver once a week, red meat twice a week, two to three eggs a week, spinach, collard greens, fish, raisins—all iron-rich foods. Choose the ones you like the best, but ensure your objective. And if the iron you need comes from your diet, you will also get enough zinc. An occasional seafood dinner, especially clams or oysters, will raise your zinc levels even more. Remember, iron and zinc are stored, so you need not get your exact requirement each day. You will want to average what you need over several days. A generous portion of oysters can supply a whole week’s zinc requirement. One large portion of liver can supply your iron requirement for several days. Try to meet your requirement for folic acid daily, since your body does not store this nutrient. This should be no problem if you eat a variety of foods listed in Table 22. Steps in planning a diet to prevent anemia are listed below:
- Set your requirement for iron, zinc, and folic acid.
- Decide on a supplement or fortified food.
- Decide on your total daily calorie intake.
- Decrease low-nutrient-density foods.
- Replace these with high-nutrient-density foods.
If you follow these simple steps, you can lower your risk for nutritional anemias by rebuilding your iron stores and keeping your bone marrow adequately supplied with zinc and folic acid.
If you are a post-menopausal female or an adult male (or suffer from a liver disorder), you should exercise caution in taking supplements which contain iron. If you take a multiple vitamin mineral supplement, maybe you should use one labeled “Silver” or “Senior,” etc. (These contain lower level of iron than the standard RDI.) If you use a “one a day” type vitamin supplement, it may be advisable for you to buy the ones without iron. There are some indications that many older people have accumulated too much iron in their bodies and that chronic conditions may be precipitated or enhanced by excessive iron storage. About one in 250 Americans has the genes for iron overload, or hemochromatosis (a genetic disorder of metabolism in which excessive levels of iron accumulate in the body). Excessive iron storage in adult men and post-menopausal women may be less rare than the genetic disorder.