Iron is an essential nutrient for all individuals as it plays a role in respiratory transport of oxygen and carbon dioxide. It forms an active part of enzymes involved in the process of cellular respiration. Although not yet clearly identified, it is involved in the immune function and cognitive performance. Iron deficiency remains a serious nutrition concern as it is one of the most prevalent nutritional deficiencies.
Dietary iron exist in two forms: heme iron, which is found in haemogolobin and myoglobin, and non – heme iron, Although heme iron accounts for only 5 – 10% of dietary iron, 25% is actively absorbed, compared to 5 % absorption of non – heme iron. Compared to non – heme iron, heme iron is less affected by dietary inhibitors.
Adults with normal haemoglobin levels absorb between 5 to 15% of dietary iron, while adults with iron deficiency can absorb up to 50%. Therefore the availability of dietary iron is a serious consideration when choosing suitable foods.
Animal proteins enhance the absorption of non – heme iron through the meat factor which is present in meat, poultry and fish. Vitamin C is the most potent enhancer of iron absorption as it forms a chelate with iron that remains soluble during absorption.
A high phytate content, such as the outer husk of cereal grains, inhibits iron absorption. Tannins found in tea, polyphenols in wine and oxalates found in dark green leafy vegetables are known iron inhibitors. Calcium and zinc supplementation may also have inhibitory effect on the absorption of non – heme iron.
Blood loss from excessive menstruation (hypermeno/ metrorrhea), gastro intestinal bleeding or visible blood loss, are some of the main causes of iron deficiency.
Inadequate iron intake is another leading cause of iron deficiency. Dietary studies have shown that iron intake among adolescents are often well below the recommended daily allowance (RDA) and 93 percent of 16 to 18 year old girls are consuming less than the recommended intake of iron.
Iron deficiency can be eliminated or reduced through optimal dietary intake of a balance between heme and non – heme iron sources. If the iron intake fails to meet the body’s iron needs or to replenish the depleted iron stores, iron deficiency anaemia will occur.
Iron deficiency is commonly identified as:
-
Depleted iron stores: bone marrow iron is absent
-
Early functional iron deficiency: biochemical measures indicate that percent transferring saturation is low
-
Iron deficiency anaemia: haemoglobin levels are below 130 g/l for males and 120g/l for females
Blood transfusion on the other hand may lead to iron toxicity in severe cases. After major surgery it is important to assess an individual’s iron status by measuring iron stores, haemoglobin levels as well as percentage transferritin saturation. Guidelines can then be subsequently developed to ensure optimal iron nutrition.