IRON as an Essential Nutrient
Iron is one of the most investigated and best understood of nutrients. Iron is essentially required as a component of the oxygen-carrying proteins myoglobin in muscle and haemoglobin in red blood cells, which transport oxygen from the lungs to various tissues around the body. Iron is also a component of several enzymes involved in chemical reactions all over the body, including those involved in cell division and growth.
It is stored in the body in the form of ferritin and homosiderin in bone marrow, liver and the spleen, and transported from these sites to cells by transferring in the blood. Iron is present in variety of food in varied quantities, but only a small percentage of the intake is actually absorbed. Heme iron (mostly in animal products) is more readily absorbed from the diet compared to non-heme iron, but absorption also depends on the level of iron stores in the body, as well as absorption enhancers (e.g. Vitamin C, copper, cobalt, manganese) and absorption inhibitors (e.g. phytic acid in whole grains and legumes, polyphenols in tea and red wine, calcium).
Deficiencies
Iron deficiency results in anaemia, i.e. small pale red blood cells with a low heamoglobin concentration. (Anaemia — A condition with lowed oxygen carrying capacity in which haemoglobin content of the blood is below the established cut of levels (WHO, 1968)).
Although many nutrients and some biological factors are involved in the maintenance of normal haemoglobin concentration, iron deficiency is the most common course of nutritional anemia and it is the most prevalent micronutrient deficiency in the world today, affecting approximately 2 billion people both in developing and developed world. Infant, preschool children, adolescents, women in child bearing age, particularly pregnant women are at the greatest risk of developing iron deficiency anaemia.
The condition is most common among women, especially when menstruating or pregnant, and symptoms include listlessness, fatigue, paleness, irritability and difficulty in swallowing.
These symptoms also present in cases haemorrhage. If severely deficient in iron, the physical capacity to work may be reduced, and an increase susceptibility to infection can result due to a decrease in white blood cells, which reduces the ability to produce antibodies as well. Anaemia in pregnancy can increase the risk of premature and low birth weight babies, and in young children, a lack of iron may be responsible for behavioral abnormalities and reduced cognitive performance, which may not be reversible with iron supplementation .
Other symptoms include, breathing difficulties, brittle nails and koilonychia and constipation, Lowered immunity, Impaired fat absorption, Increased lead absorption with its negative consequences.
Excessive Intake
Over supplementation can cause adverse effects. Athletes who take iron supplements to enhance their training performance may be more prone to recurrent illness and infections because bacteria have been known to thrive in iron rich environments.
Babies who are fed iron fortified formulas may also suffer from symptoms of excess iron, causing the proliferation of foreign bacteria in the gut and proceeding discomfort from gas and bloating. (Babies are born with naturally high levels of tissue irons, enough for a year of normal growth, and therefore do not require iron supplements). Iron poisoning can occur if children accidentally consume adult doses of iron supplements, and toxicity can also occur from coking in cast iron pans. There is also a condition called haemochromatosis, which results in the individual suffering from excessive iron stores. Other possible causes of excess iron identified include repeated blood transfusions and chronic alcoholism. Symptoms of toxicity are vomiting, diarrhea, and intestinal damage.
Dietary Iron and Bio-availability
The absorption of iron from the meal depends on individual iron status and requirement, on the sources and on content of iron within the meal and on the other constituents. Iron is present in food in both inorganic/ non haem (ferric, ferrous) and organic (mostly haem) forms. The haem iron pool include all food components that have iron as part of haem molecule. The absorption of haem iron molecule in not modified by most inhibitors and enhancers of iron absorption except dietary proteins which increase haem iron absorption and calcium, magnesium which inhibit it. Non haem iron pool contain all other sources of iron. Non haem iron usually bound with phenolic compounds in most seeds and vegetable tissues while non haem iron also can be found in milk and eggs. These non haem iron absorption be affected by many dietary components. Haem iron containing proteins, ascorbic, malic, tartaric, succinic acids and some fermentation products are enhancers of non haem iron uptake. Meat and alcohol also enhance non haem iron absorption by promoting gastric acid production. Inhibitors include phytic acid and other polyphosphates, fibre, calcium, manganese, polyphenols such as tannins and other compounds present in foods and beverages, especially tea, coffee, chocolate and herbal infusions. The absorption of non haem iron can vary very widely.
Iron can be found in different food sources in varied quantities while some food can be categorized as rich iron sources. Foods rich in iron include:
- Red meat, pork and poultry
- Seafood
- Vegetables Clams, oysters
- Dark green leafy vegetables, such as spinach.
- Dried fruit (e.g.: raisins and apricots)
- Wholegrain cereals
- Iron-fortified cereals, breads and pastas and other iron fortified foods.
