Minerals Required in Larger Amount

We  have just  mentioned  some of the  minerals required  by our body. Of these calcium, phosphorus, sodium, potassium, chloride and magnesium are the minerals required in larger amounts by the body. This set of minerals constitute more than three-fourths of the  total mineral content of the body.

Some minerals required by the body

Let us now begin the study of minerals with calcium and phosphorus. You may wonder why we are discussing calcium and phosphorus together. This is because they work  in coordination with each other. In fact such coordinated activity is typical of minerals. 

Calcium and Phosphorus 

Of all the minerals  found  in our body  calcium and  phosphorus are by far present in the largest amount. Together these two minerals account for 75 percent  of the total mineral content of the body. The human body contains approximately 1200g of calcium, most of which is present in bones and teeth and the remaining in soft tissues and in the body fluids. On the other hand, only 400-700g of phosphorus is contained in  the body. Like calcium  most of it is also  present  in  bones and teeth and the remaining in soft tissues and body fluids. 

Functions: What role do calcium and phosphorus play in our body? Calcium and phosphorus basically serve two  important functions in the body one  relating to the development of bones and teeth and the other to the regulation of body processes. 

1. Development of bones and teeth: Calcium and  phosphorus are mainly  present in bones  and teeth. The ratio of calcium and phosphorus in the bones is  roughly 2:l. Calcium in the bone combines with phosphorus, some other minerals and water to form a compound. It is this compound which provides rigidity and firmness to the bones. Teeth, like the bones also require calcium for their proper development. It is for this reason that the need for calcium is the most during the growing years. 
2. Regulation of body  processes: Apart from building  bones and teeth, calcium and phosphorus perform  regulatory  functions as well. 

Calcium helps in: 

1.  regulating the contraction  and relaxation of muscles  especially that of the heart 
2.  regulating the passage of substances into and out of the cells 
3.  conveying  messages from one nerve cell to another and 
4.  the  clotting of blood. 

Phosphorus also  performs several important functions. It is  required for the: 

1. formation of a substance which aids-in transport of fat in  the blood 
2. synthesis of certain coenzymes which play a crucial role in  metabolism 
3. formation of certain basic genetic material. This genetic material is  involved in  passing on of specific characteristics from  to children and 
4. capture and storage of vital  energy in the cells  of many tissues by forming a high-energy compound. Muscle tissue is a prominent  example where phosphorus helps in energy storage and thus fuels muscle contraction. 

Food sources: Which  foods provide good amounts of calcium? Milk and milk products like curd, khoa, channa (cottage cheese) are excellent  sources of  calcium. Foods like fish (e.g. chingri,  chela) especially dried fish and other sea foods (e.g. crab,  shrimp) provide substantial quantities of calcium. 

Among  the  plant sources, ragi (a millet grown in South India) is particularly rich in calcium.  Pulses like bengal gram, black gram, green gram, moth beans, rajmah, soyabean contribute  substantial amounts of calcium. Green leafy vegetables  (like amaranth leaves, colocasia leaves, fenugreek leaves, mustard leaves) also contain good amounts. Among nuts and oilseeds,  gingelly (til) seed is particularly rich  in calcium. Others like coconut, almonds, walnuts have a  fairly good amount of calcium. 

As for  the sources  of phosphorus, a diet that furnishes enough  protein and calcium would normally  provide sufficient phosphorus. Eggs, milk, poultry, fish are excellent sources  of phosphorus. Cereals too are rich sources  of  this  mineral. 

Absorption  and  utilization: Calcium is absorbed chiefly from  the  upper part of the  intestine.  Normally it is seen that from an average  Indian  diet only 20-30 per cent of calcium  gets absorbed. The rest is excreted in the faeces. The absorbed calcium is then used to perform various functions as has been discussed earlier. Part of  the absorbed calcium is also excreted in the  urine but the  amount is  very small.

We mentioned  earlier that only a  small proportion of the calcium in  the diet is absorbed. What are the reasons for this? You will find the  answer  as you read about the factors influencing calcium absorption. Let us  now study these factors and try to understand how they  influence calcium absorption. The factors include: 

1. Body need: The efficiency of absorption of calcium  increases during periods of rapid growth i.e. infancy, childhood, pregnancy, lactation. When  the body's demand for calcium increases the absorption of calcium alse increases to meet this  increased demand. 
2. Nutrients in  the diet: Certain  nutrients like vitamin D, protein and carbohydrate present in the  diet help to improve absorption of calcium. Another nuirient that influences  calcium absorption is phosphorus. In fact the proportion of calcium and phosphorus in the  diet affects  calcium absorption. Excess phosphorus tends to lower  calcium absorption. 

   

   Nutrients that increase  calcium absorption 

3. Inhibitors: Inhibitors  are  substances  present in food which hinder calcium absorption. You have learnt earlier that cereals and green  leafy  vegetables are rich  in  calcium. But all the calcium present  in these foods is  not available to the body. This is because  these food items  have some  substances (such as phytates in  cereals and oxalates in green  leafy  vegetables)  present in them which  bind  calcium and inhibit its absorption. 

So far you  have read about absorption and excretion of calcium. Let us now study about absorption and excretion of phosphorus. As in the case of calcium, absorption of phosphorus also takes place from the upper  part of the small intestine. However, a considerable amount of phosphorus in cereals, pulses and nuts exists in  a bound form which is not absorbed. The body takes in only the free form. The absorbed phosphorus  then gets used in the body and  performs various functions as has been  discussed earlier.

Sodium :

An adult body contains approximately 120 g of sodium. Most of this is  present in the  extra cellular fluid. Extra cellular fluid  refers to the fluid outside the cell just as  intracellular fluid  refers to fluid  inside the cell. One  example of extra cellular fluid is blood  plasma. You may remember that blood  has two parts cells and plasma. The term  plasma refers to  the fluid part of the blood. Let us now learn what role sodium plays in our body.

Minerals present in the  body  fluids

Functions: Some of the important functions of sodium are listed here:

1. Regulating the  balance of extra cellular and intracelluler fluid: Sodium, the principal  mineral in the extra cellular fluid is responsible for maintaining the fluid balance. By fluid balance we mean  the process of maintaining a balance between the fluid present within  the cells (intracellular) and  that circulating outside  the cells (extra cellular). Sodium along with  potassium (another mineral)  helps to  maintain this  balance. 
2. Regulating the  alkalinity and  acidity of the  body fluids: Sodium tends to make the  body fluids alkaline. Another mineral  namely chloride present in the body fluids  tends to make  them acidic. Sodium combines with chloride in the fluid and together they help maintain  the balance between the alkalinity and acidity of the  body  fluids. 
3. Aiding in  the  passage of messages from one nerve  cell to another. 
4. Aiding the contraction of muscles and 
5. Regulating the  passage of substances into  and out of the cell. 

Food sources: Do you  know what items in our diet  provide maximum sodium? You are familiar  with common table  salt  which is  nothing but sodium chloride. Common table salt is the principal source of sodium in our diet.  One  teaspoon of salt provides almost 2000 mg sodium. Other rich sources of sodium include  milk, egg white, meat, poultry, fish among the animal foods and green leafy  vegetables (such as spinach, fenugreek leaves) and pulses among the plant sources.

Absorption and excretion: Sodium ingested is  readily absorbed by the digestive tract  and used for various  body functions. The excess amount of sodium over and above body needs  is  lost from the body through urine, sweat, and faeces. Sodium losses are high whenever we sweat more as in hot weather. Any disease condition in  which water is lost from  the  body  also causes excessive sodium loss. A common example is diarrhoea i.e. loose motions. Excessive sodium loss is  not good as it affects the fluid balance of the  body. This requires  special attention. Intake of fluids and salt  should  be increased during such times so as to make up for the loss.

The major  regulation of the amount of sodium in the  body is done by the kidneys by varying the total amount of urine  excreted. When intake of sodium increases, excretion increases and when intake decreases, excretion decreases. This process helps to keep the  body concentration of sodium within normal limits.

Potassium:

Potassium is present  in twice as much amount as sodium in the body. Approximately 250g of potassium is contained in the body and most of this ispresent  in the cells i.e.  in the intracellular  fluid. When you read this  section, you will find  how  closely the functions of sodium and potassium are interlinked.

Functions: The functions of potassium include:

1. Regulation of the  balance of intracellular and  extracellular fluid: Potassium along with sodium helps maintain fluid balance  within the cell and  outside the cell.  You  have learnt  earlier that sodium is the main  mineral present in extracellular fluid (the fluid outside the cell). Potassium on the  other  hand, is the principal mineral in the intracellular fluid.  Together these two minerals  help maintain fluid balance.
2. Regulation of the alkalinity/acidity of body fluids: Potassium, like sodium, is alkaline. It  combines with chloride which is acidic and together they help maintain the acidity/alkalinity of body  fluids.
3. Role in muscle  activity: Potassium has a significant  role in the activity of skeletal and heart muscle. It helps in  the  transmission of messages  which  results in the  contraction of muscle tissue.

Food sources: Potassium is widely distributed in foods. Meat, poultry and fish are good  sources. Among the plant  foods, pulses, fruits. vegetables especially the green leafy vegetables are good sources of potassium. The water of the tender coconut is. however. the best source of potassium. Among the other fruits and vegetables, bananas,  potatoes, carrots, tomatoes and lemons contain appreciable amounts of this mineral. Whole grain cereals also provide some amounts of potassium.

Absorption and excretion: What  happens to potassium once it  enters  the body? Potassium gets absorbed from the upper part of the intestine.  The absorbedpotassium then gets used up  to perform the  various  body funtions discussed earlier. Excess potassium is excreted In the urine and the faeces.

Chloride:

The body contains approximately 100 g of chloride and most of this is  found in the extracellular fluid (especially in  the blood plasma). The rest of the  chloride ispresent  inside the cell. Chloride is  present in  the extracellular fluid as sodium chloride and in the cell as potassium  chloride.

Functions: The functions of sodium, potassium and chloride are closely interlinked as is evident from our earlier discussion. Chloride combines with sodium and potassium and helps regdate fluid balance and acidity/alkalinity of body fluids.

Food sources: Chloride is  widely distributed in all  plant  foods. But the most important  source of chloride in our diet is common table salt i.e.  sodiumchloride.

Absorption and excretion: Chloride is  readily absorbed from the upper part of the intestine. Excess chloride, as in the case of sodium, is excreted in the urine and to a lesser extent  through the sweat and the faeces.

Megnesium
The adult human body  contains approximately 20-25g  of magnesium. About 60-70 percent of this magnesium is present in the  bones in  combination with calcium and phosphorus. The remaining 30-40 per cent is distributed in  various tissues and body fluids mostly in the  intracellular fluid.
Functions: Magnesium helps in :

1. regulating the passage of substances into and out of the cells
2. maintaining the activity of many enzymes. Magnesium functions as a coenzyme in metabolism
3. building bones and teeth.  It  is involved in  bone mineralization
4. maintaining the functions of the nervous  system, whereby it kelps in the passage of messages from one nerve  cell to another
5. maintaining smooth muscle action and
6. building  proteins.

Sources: Which are the food sources that are rich in magnesium?  Magnesium is widely distributed in plant foods. The most concentrated sources of magnesium include nuts (groundnut, cashewnut, walnut, almond), oilseeds (sesame seeds), pulses (rajmah, moth beans, soyabean), whole grains (wheat, bajra, jowar). Among sea foods shellfish is particularly  rich in magnesium. Other foods which contain appreciable amounts of magnesium include dark green leafy vegetables,  peas, lotus stem, fish (Salmon, haddock), sea foods (crab, oyster) and meat.

Absorption and excretion: Magnesium is absorbed from  the small intestine. The absorption of magnesium in the body is somewhat similar to that of calcium. When the body's demand increases, the absorption increases so as to meet the increased demand.Further, factors that interfere with calcium absorption such as the presence of inhibitors in the  diet also  interfere  with  magnesium absorption.

The  excretion of  magnesium by the body is regulated by the kidneys.