Minerals Required in Smaller Amounts

You have just  studied about the minerals  required in  larger amounts by the body. There are  other minerals  required in very small amounts by our body.  These minerals are called trace elements. Just a tiny amount required,  but  what significant functions they  perform!  Minerals like iron, iodine, zinc and copper belong to this group. Let  us begin our study of trace elements  with iron. 

Iron 

Iron is a trace element present in the body to the extent of 3-5g. Compare this to a mineral like calcium which, as you learnt earlier, is present in the body to the extent of 1200g. Where is iron found in the body? Most of it is found in the blood (about 75 percent). All cells and tissues especially the muscle tissues contain a  little iron (about 5 percent) and the rest  of the iron i.e. about 20 percent is stored in the body organs such as the liver, spleen,  kidney and bone marrow collectively. 

Functions: The study of iron and its functions is fascinating. After many  years of research, there are still many puzzling aspects about the role of iron, especially about those related to brain functioning. Let us now study some of the known and well established functions of iron. 

Haemoglobin as a carrier for oxygen and carbon dioxide

1. Oxygen transport: lron is a major constituent of a red-coloured compound called haemoglobin present in the blood. Iron is present in the haem part of haemoglobin.What is the role of haemoglobin?. Haemoglobin is necessary for transport of oxygen to various parts of the body. Haemoglobin  carries oxygen from the lungs to the tissues and in turn helps  in carrying carbon dioxide from the tissues to the lungs as indicated. From the lungs carbon dioxide is then exhaled out. Carbon dioxide, in fact, is a waste product formed in all cells as a  result of metabolism and it needs to be removed from the body. 
2. Provision of oxygen for muscle contraction: Iron is also present in the muscle in the form of myoglobin. Myoglobin has the capacity to store oxygen. This oxygen is used for muscle contraction and for other immediate needs of the muscle cells. 
3. Promotion of oxidation within cells: iron facilitates the complete oxidation of carbohydrates, fats and proteins within the cell. This, of course, would result  in the release of the energy locked up in these molecules. The role of iron in oxygen transport and release of energy is now clear to you. You know that energy is required for the various physical  activities we perform every day. This is the reason why iron is crucial in helping us to perform physical work. 
4. Iron plays an important role in maintenance of specific brain functions like immediate memory, capacity to learn and attention span. 
5. Iron forms a vital component of certain enzymes and substances that aid in metabolism. 
6. Iron has protective functions as well. Like vitamin A, iron too helps in preventing infections. 

Food sources: Are you familiar with the rich food  sources of iron? Liver is an excellent source. Other organ meats like kidney, spleen also contain substantial amounts of iron. Among the plant foods the list of iron sources includes green leafy vegetables (like amaranth leaves, mustard leaves, colocasia leaves, mint leaves), 

cereals (like whole wheat flour, rice flakes, bajra, ragi, jowar) and pulses (especially the whole ones). Soyabean is an example of a pulse containing good amounts of iron. Jaggery is another food that contains fair amounts of iron. 

We have mentioned several foods which contain substantial amounts of iron. However, we have a paradoxical situation here. There is so much of iron present in food and yet very little gets into the body. Why is this so? You  would find the answer to this question in the subsequent section. 

Absorption and excretion:  What  happens to iron once it enters the body? The ingested iron gets absorbed from the upper part of the intestine. The extent of iron absorption from different foodstuffs varies. In general, its absorption from animal foods is high. But the amounts of iron absorbed from many of the plant sources is very  low. This is because certain substances present in plant foods bind iron and hinder its absorption. These substances are called inhibitors. You would  remember reading earlier the some plant foods such as green leafy vegetables and cereals contain fairly substantial amounts of iron. Unfortunately they also contain inhibitors which prevent much of the iron from being absorbed. On the other hand, there are substances like protein and vitamin C present in foods that aid in the absorption of iron. These substances can be called enhancers. It is, therefore, suggested that protein-rich foods like milk and vitamin C-rich foods like oranges, lime, amla and guava should be included in the diet so as to promote the absorption of iron. The inclusion of animal foods, if  possible, in the diet greatly enhances iron absorption. 

After absorption, iron is transported by the blood to the body cells where it performs its varied functions. Some amount of iron is also transferred to the storage sites in the body such as the liver, spleen, kidney and the bone marrow. Very small amounts of iron are lost through sweat and urine. In the cage of women, iron losses include the above but in addition fairly substantial amounts are lost in the menstrual flow.

Nutrients that increase iron absorption 

Iodine 

Do you remember the last time you went to buy salt? You would probably have noticed the packets of iodized salt. Iodized salt, in fact, is table salt to which iodine is added. But why are we taking so much care to add iodine to the salt? Why  is iodine so important? Let us try to find out.

Iodized salt

The adult body contains a very small amount of iodine which amounts to only 20-25 mg. The maximum concentration of this mineral is found in the thyroid gland which is located  in the neck region. 

Functions: Why do we need iodine? Iodine is a component of the hormone thyroxine secreted by the thyroid  gland. Thyroxine regulates the rate of oxidation within the cells. If this regulation does not take place, both physical and mental growth will be affected. Iodine is also believed to help in the functioning of nerve 

and muscle tissues.

Food sources: The amount of iodine in most foods is limited and it baries widely depending on the iodine content of soil and water. Crops such as vegetables especially those grown in coastal areas where iodine content of the soil is high have substantial amounts of iodine. In hilly areas, however, the iodine content of both the soil and water is low. Hence the crops grown in such areas contain  little iodine.

The iodine content of animal foods like eggs, dairy products and meat depends, of course, on the iodine content of the food that is part of the animal's diet. Sea foods like fish, shell fish are among the best sources of iodine. 

It is now known that soils are deficient in iodine not only in the hilly regions but in several other parts of our country. This means that the foods grown in these areas would also be poor in iodine. In such a situation it becomes important to ensure that iodized salt forms a part of the daily diet. 

Another aspect that needs mentioning here is that certain plant  foods like cabbage, cauliflower, radish, ladies finger, groundnuts and oilseeds contain substances called goitrogens which interfere with the body's ability to produce and use thyroxine. Goitrogens can be easily destroyed on thorough cooking. Hence it is advisable to cook the foods mentioned above properly before eating. 

Absorption and excretion: Dietary  iodine is absorbed in the small intestine in the form of iodides (compounds of iodine). These iodides are carried by the blood to the thyroid gland. About one-third of the iodine is picked up by the thyroid gland and the rest is excreted.