Iron is a mineral, essential in the metabolism of almost all living organisms. It is vital to the health of the human body, and is found in every human cell. It is an important element for the formation of haemoglobin and transports oxygen to all parts of the body. Iron gives blood its characteristic red color.
Iron is an essential component of haemoglobin and almost two-thirds of iron in the body is found in hemoglobin. Some of it is distributed in myoglobin, a protein that helps supply oxygen to the muscles, especially to skeletal muscles and to the heart. It forms a part of enzymes which take part in biochemical reactions in the body and is stored in liver, spleen and bone marrow for future use.
The primary function of iron in the body is to transport oxygen. The iron in haemoglobin combines with oxygen and transports it to the tissues and organs in the body. If we are deficient in iron, less hemoglobin will be produced, and therefore the supply of oxygen to our tissues will also be less.
Iron is an important component of proteins which are essential for respiration and energy metabolism. It helps in energy production and is needed for proper functioning of the immune and central nervous systems. It also forms a part of an enzyme which is required for DNA (deoxyribonucleic acid) synthesis.
There are two forms of dietary iron: heme and nonheme. The absorption of the two types of iron differs, with heme iron being more readily absorbed (about 20%) than nonheme iron (about 2%-20%). Animal sources of iron include red meat, especially liver and eggs. Nonheme sources of iron include dark green leafy vegetables, especially spinach, whole grains such as wheat and oats, legumes, nuts seeds, dried fruit and enriched cereals. Cooking in iron pots and pans also increases the amount of iron consumed.
The absorption of iron (especially nonheme iron) from food is greatly influenced by certain factors. Factors which increase the absorption of nonheme iron are called enhancers, while those that decrease it, are called inhibitors. Vitamin C enhances the absorption of nonheme iron and must be consumed with iron at the same meal.
Inhibitors of nonheme iron include phytates and oxalates. Phytates are present in whole grains and legumes while oxalates are present in vegetables like spinach. Soy protein, polyphenols found in some fruits and vegetables, coffee, tea and wines, also inhibit the absorption of nonheme iron from the food.
To get enough iron, a wide variety of foods rich in iron should be consumed. When iron intake from plant foods is relatively high and a variety of foods is consumed, inhibitors and enhancers of iron absorption can offset each other and iron balance is not adversely affected.
The recommendations for iron (milligrams/ day) by the Institute of Medicine at the National Academy of Sciences in the year 2000 are given as below:
- Boys 14-18 years: 11 milligrams (mg)
- Girls 9-13 years: 8 mg
- Girls 14-18 years: 15 mg
- Men 19 years and above: 8 mg
- Women 19-50 years: 18 mg
- Women 51 years and above: 8 mg
- Pregnant women 14-50 years: 27 mg
- Lactating women 14-18 years: 10 mg
- Lactating women 19-50 year: 9 mg
Adult men and women and adolescent girls on a vegetarian diet require greater amounts of iron. Refer to What can high-iron foods do for you?
Iron deficiency (depleted body iron stores) is one of the foremost nutritional disorders in the world. It develops gradually and the iron stores are first depleted to maintain normal blood levels. Once the storage sites become deficient and blood levels of iron cannot meet daily needs, it results in iron deficiency anemia. People at risk of iron deficiency anemia include women of childbearing age, pregnant women, teenagers, low birth-weight infants and people with some gastrointestinal disorders, when they cannot absorb iron normally.
Iron deficiency anaemia is characterized by underdeveloped red blood cells that lack haemoglobin. The symptoms of mild iron deficiency include non specific symptoms such as fatigue, weakness, headache and irritability. People with iron deficiency anemia experience paleness, decreased work performance, increased susceptibility to infection due to decreased immune function, brittle nails, loss of appetite and inadequate temperature regulation.
Iron deficiency is not the only cause of nutritional anemia, the others being deficiency of folic acid and vitamin B12. Therefore, proper diagnosis of the underlying cause is important before treatment of anemia can start.
Iron overload or toxicity from food sources alone is very rare. However, there are other conditions which can lead to accumulation of iron in the tissues and organs of the body. These include a genetic predisposition to absorb more iron than normal, leading to high iron stores. The symptoms associated with excessive iron storage include dizziness, nausea, loss of appetite, headaches and shortness of breath. Acute ingestion of large quantities of iron-containing supplements can also lead to iron poisoning.
- Dietary Supplement Fact Sheet: Iron
- What can high-iron foods do for you?
- Information Sheet - Iron