Dr Ng Min Ching
Iron deficiency is one of the most common nutritional deficiencies in Singapore, and the world as a whole. If neglected, it can cause the concentration of haemoglobin in red blood cells to fall below normal resulting in iron deficiency anaemia. The good news is that iron deficiency can be corrected with a few additions to your diet.
What iron does for you
Iron is mainly found in haemoglobin, an oxygen-carrying protein found in red blood cells. Haemoglobin is essential for delivering oxygen from the lungs to the body's tissues. Severe deficits in the delivery and use of oxygen increase fatigability, decrease work capacity, impair brain function, and lessen ability to maintain body temperature.
Thus, people who are anaemic often tire easily and become breathless on mild exertion. Giddiness, palpitations and general weakness are also common symptoms of anaemia. Physical examination may reveal spoon shaped brittle nails (i.e. the nail has a concave surface). The corners of the mouth may sometimes dry and crack, and the tongue may atrophy. In rare cases, the spleen is enlarged as well.
What causes iron deficiency
Iron deficiency usually arises because of the following:
1. Blood loss. This is the most common cause of an iron deficient state and menstrual blood loss is the main culprit in women of childbearing age who are iron-deficient. Blood loss can be obvious, as in excessive menstrual flow and major trauma. It can also be insidious, as in peptic ulcer, intestinal cancer and hookworm infestation.
2. Increased iron requirements. Infants and adolescents require more dietary iron, as they are experience growth spurts. Mothers-to-be also need more iron for the developing foetus as it plays a crucial role in the function of the immune and central nervous systems. Hence, infants who are more than six months in age should be fed iron-fortified cereals and an iron-rich diet, while pregnant women should be prescribed iron supplements.
3. Insufficient dietary iron. This occurs when red meat, wheat, cereals and other good sources of dietary iron are not consumed in adequate amounts.
4. Decreased absorption of iron. Conditions like malabsorption and chronic diarrhoea can impair iron absorption.
How much iron do you need?
Most people do not meet the daily requirement for iron. About 1mg of iron is lost daily in the cells shed from the skin, gastrointestinal tract and genitourinary tracts. Iron absorption occurs in the small intestine and only 10 percent of dietary iron is absorbed. Therefore, only 1mg is taken into the body when 10mg of dietary iron is consumed. This amount is just sufficient to replace the daily iron loss. Any less and the body will start losing iron.
Women are at a higher risk of developing iron deficiency because iron is lost in menstruation. Approximately 40ml of blood is lost per menstrual period which translates into about 0.5mg of iron per day. Pregnant women, on the other hand, lose about 0.5-0.8mg of iron a day.
Moreover, a healthy adult male has 3.5g of total body iron whereas that of an adult female is only 2.5g. Hence, women usually need to increase the intake of iron in their diet.
* The daily iron requirement of a pregnant woman usually cannot be met by the amount of iron in the diet. Hence a daily iron supplement is needed.
Who needs supplements?
Iron deficiency usually corrects itself when you replenish the store of body iron. Red meat, liver, wheat, cereal, green leafy vegetables and prunes are excellent sources of iron. For example, 3 ounces of red meat contain 2-3mg of iron, 3 ounces of liver contain 8-25mg of iron, a cup of green leafy vegetable and a cup of prunes both contain 4mg of iron and 1 ounce of total cereal has 18mg of iron.
Vitamin C increases the absorption of iron while tea, coffee, phosphates, EDTA (a preservative in food) and magnesium trisilicate (in antacids) impair iron absorption.
Supplements are only recommended if youhave been diagnosed by a doctor as being iron deficient. Consuming too much iron results in iron overload where the excess iron is deposited in organs such as the liver, heart and pancreas. Multi-organ damage and death eventually occurs.
However, taking these daily supplements can cause abdominal discomfort or pain, constipation or diarrhoea and the passing of black stool. To reduce the incidence of these side effects, take the supplements with your meals. If you are not able to tolerate oral iron preparations, or have very poor intestinal absorption of iron as a result of certain gastric and small intestinal disorders, your doctor may suggest a jab.
- Braunwald, isselbacher, Petersdorf, Wilson, Martin, Fauci. Harrison's Principles of Internal Medicine, 11th edition. (1987). MacGrraw-Hill Book Company, New York, U.S.A.
- The Merck Manual of Diagnosis and Therapy, www.merck.com/pubs/manual/section11/chapter127/127c.thm
Date reviewed: 05 April 2000