Biological Important Minerals

In the context of nutrition, a mineral is a chemical element required as an essential nutrient by organisms to perform functions necessary for life. Minerals originate in the earth and cannot be made by living organisms. Plants get minerals from soil. Most of the minerals in a human diet come from eating plants and animals or from drinking water. As a group, minerals are one of the four groups of essential nutrients, the others of which are vitamins, essential fatty acids, and essential amino acids.

The five major minerals in the human body are calcium, phosphorus, potassium, sodium, and magnesium. All of the remaining elements in a human body are called “trace elements”. The trace elements that have a specific biochemical function in the human body are sulfur, iron, chlorine, cobalt, copper, zinc, manganese, molybdenum, iodine and selenium.

GENERAL FUNCTIONS:

The general function of minerals and trace elements can be summarised as follows:

•  Minerals are essential constitutents of skeletal structures such as bones and teeth.
•  Minerals play a key role in the maintenance of osmotic pressure, and thus regulate the exchange of water and solutes within the animal body.
•  Minerals serve as structural constituents of soft tissues.
•  Minerals are essential for the transmission of nerve impulses and muscle contraction.
•  Minerals play a vital role in the acid-base equilibrium of the body, and thus regulate the pH of the blood and other body fluids.
•  Minerals serve as essential components of many enzymes, vitamins, hormones, and respiratory pigments, or as cofactors in metabolism, catalysts and enzyme activators.

Macroelements

Calcium

Biological function:

•  Calcium is an essential component of bone, cartilage and the crustacean exoskeleton.
•  Calcium is essential for the normal clotting of blood, by stimulating the release of thromboplastin from the blood platelets.
•  Calcium is an activator for several key enzymes, including pancreatic lipase, acid phosphatase, cholinesterase, ATPases, and succinic dehydrogenase.
•  Through its role in enzyme activation, calcium stimulates muscle contraction (ie. promotes muscle tone and normal heart beat) and regulates the transmission of nerve impulses from one cell to another through its control over acetylcholine production.
•  Calcium, in conjunction with phospholipids, plays a key role in the regulation of the permeability of cell membranes and consequently over the uptake of nutrients by the cell.
•  Calcium is believed to be essential for the absorption of vitamin B12 from the gastro-intestinal tract.

Dietary sources and absorption: Rich dietary sources of calcium include limestone, oystershell grit, bone meal, rock phosphate (40–30%); white fish meal, poultry manure, meat meal (10–5%); and brown fish meal, D-lactose powder, dried skim milk, poultry by-product meal, beans, leafy vegitables, cabbage, egg yolk. Calcium is readily absorbed through the gastro-intestinal tract (through vitamin D3 action).

Phosphorus

Biological function:

•  Phosphorus is an essential component of bone, cartilage and the crustacean exoskeleton.
•  Phosphorus is an essential component of phospholipids, nucleic acids, phosphoproteins (casein), high energy   phosphate esters (ATP), hexose phosphates, creatine phosphate, and several key enzymes.
•  As a component of these important biological substances, phosphorus plays a central role in energy and cell metabolism.
•  Inorganic phosphates serve as important buffers to regulate the normal acidbase balance (i.e. pH) of animal body fluids.

Dietary sources and absorption: Rich dietary sources of phosphorus include rock phosphate, dicalcium phosphate, bone meal (20–10% P); meat and bone meal, meat meal, white fish meal, poultry by-product meal, milk, cereals, leafy vegetables, meat, eggs. Phosphate absorption occurs from jejenum. Calcitriol promotes phosphate uptake along with calcium. Acidity favours while phytate decreases phosphate uptake by intestinal cells.

Magnesium
Biological function:

1.  Magnesium is an essential component of bone, cartilage and the crustacean exoskeleton.
2.  Magnesium is an activator of several key enzyme systems, including kinases, (ie. enzymes that catalyse the transfer of the terminal phosphate of ATP to sugar or other acceptors), mutases (transphosphorylation reactions), muscle ATPases, and the enzymes cholinesterase, alkaline phosphatase, enolase, isocitric dehydrogenase, arginase (magnesium is a component of the arginase molecule), deoxyribonuclease, and glutaminase.
3. Through its role in enzyme activation, magnesium (like calcium) stimulates muscle and nerve irritability (contraction), is involved in the regulation of intracellular acid-base balance, and plays an important role in carbohydrate, protein and lipid metabolism.

Dietary sources and absorption: Rich dietary sources of magnesium include; meat and bone meal, sunflower seed meal (1.0–0.75% Mg); and cereals, nuts, beans, vegetables, meat, milk, fruits.Magnesium is readily absorbed through the gastro-intestinal tract. About 50% of the dietary Mg is normally absorbed.

Sodium, Potassium and Chlorine
Biological function: Sodium, potassium, and chlorine occur almost entirely in the fluids and soft tissues of the body, sodium and chlorine being found mainly in the body fluids, and potassium occuring mainly in the cells. They serve a vital function in controlling osmotic pressures and acid-base equilibrium. They also play important roles in water metabolism.

1.  Sodium is the main monovalent ion of extracellular fluids; sodium ions constituting 93% of the ions (bases) found in the blood stream. Although the principal role of sodium in the animal is connected with the regulation of osmotic pressure and the maintenance of acid-base balance, sodium also has an effect on muscle irritability, and plays a specific role in the absorption of carbohydrate.
2.  Potassium is the major cation of intracellular fluid, and regulates intracellular osmotic pressure and acid-base balance. Like sodium, potassium has a stimulating effect on muscle irritability. Potassium is also required for glycogen and protein synthesis, and the metabolic breakdown of glucose.
3.  Chlorine is the main monovalent anion of extracellular fluids; chlorine ions constituting about 65% of the total anions of blood plasma and other extracellular fluids within the body (ie. gastric juice). Chlorine is therefore essential for the regulation of osmotic pressure and acid-base balance. Chlorine also plays a specific role in the transport of oxygen and carbon dioxide in the blood, and the maintenance of digestive juice pH.

Dietary sources and absorption: The dietary sources of sodium and chlorine include: The common salt (NaCl) used in the cooking medium is the major source of sodium. The good sources of sodium include bread, whole grains, leafy vegetables, nuts, eggs and milk.

The dietary sources of potassium are Banana, orange, pineapple, potato, beans, chicken and liver. Tender coconut water is rich sources of potassium.

Potassium, sodium and chloride are readily absorbed from the gastrointestinal tract.
Sulphur
Biological function: Sulphur is an essential component of several key amino acids (methionine and cystine), vitamins (thiamine and biotin), the hormone insulin, and the crustacean exoskeleton.

•  As the sulphate, sulphur is an essential component of heparin, chondroitin, fibrinogen and taurine.
•  Several key enzyme systems such as coenzyme A and glutathione depend for their activity on free sulphydryl (SH) groups.
•  Sulphur is believed to be involved in the detoxification of aromatic compounds within the animal body.

Dietary sources and absorption: Rich dietary sources of the sulphur containing amino acids include fish meal, chicken eggs. Sulphur containing amino acids and to a lesser extent inorganic sulphates are readily absorbed from the gastrointestinal tract of fish and shrimp.

Microelements

Iron

Biological function:

•  Iron is an essential component of the respiratory pigments haemoglobin and myoglobin.
•  Iron is an essential component of various enzyme systems including the cytochromes, catalases, peroxidases, and the enzymes xanthine and aldehyde oxidase, and succinic dehydrogenase.
•  As a component of the respiratory pigments and enzymes concerned in tissue oxidation, iron is essential for oxygen and electron transport within the body.

Dietary sources and absorption: Rich sources are organ meats (liver, heart, spleen), Good sources are leafy vegetables, pulses, cereals, fish, apples, dried fruits, molasses and poor sources are milk, wheat and polished rice. Iron is readily absorbed in the stomach and duodenum. Dietary iron availability and absorption is usually depressed by high dietary intakes of phosphate, calcium, phytates, copper and zinc. In general, inorganic sources of iron are more readily absorbed than organic sources; the ferrous iron (Fe++) being more available for absorption than ferric iron (Fe+++). Reducing substances such as vitamin C enhance the absorption of non-haem iron.

Zinc
Biological function:

• Zinc is an essential component of more than 80 metalloenzymes, including carbonic anhydrase (required for the transport of carbon dioxide by the blood and for the secretion of HCI in the stomach), glutamic dehydrogenase, alkaline phosphatase, pyridine nucleotide dehydrogenase, alcohol dehydrogenase, superoxide dismutase, pancreatic carboxy peptidase.
•  Zinc serves as a cofactor in many enzyme systems, including arginase, enolase, several peptidases, and oxalacetic decarboxylase.
•  As an active component or cofactor for many important enzyme systems zinc plays a vital role in lipid, protein, and carbohydrate metabolism; being particularly active in the synthesis and metabolism of nucleic acids (RNA) and proteins.
•  Although not proven, it has been suggested that zinc plays a role in the action of hormones such as insulin, glucagon, corticotrophin, FSH and LH.
•  Zinc is believed to play a positive role in wound healing.

Dietary sources and absorption: Rich sources of meat, fish, eggs, milk, beans, nuts. Zinc is readily absorbed from the gastro-intestinal tract. Dietary zinc availability and absorption is reduced in the presence of phytates, and high dietary intakes of calcium, phopshorus and copper.

Manganese
Biological function:

•  Manganese functions in the body as an enzyme activator for those enzymes that mediate phosphate group transfer (ie. phosphate transferases and phosphate dehydrogenases), particularly those concerned with the citric acid cycle including arginase, alkaline phosphatase and hexokinase.
•  Manganese is an essential component of the enzyme pyruvate carboxylase
•  As a cofactor or component of several key enzyme systems, manganese is essential for bone formation (re. mucopolysaccharide synthesis), the regeneration of red blood cells, carbohydrate metabolism, and the reproductive cycle.

Dietary sources and absorption: Rich sources of cereals, nuts, leafy vegetables, and fruits. Tea is rich sources of Mn. Manganese is readily absorbed from the gastro-intestinal tract. Iron inhibits Mn absorption.

Copper
Biological function:

•  Copper is an essential component of numerous oxidation-reduction enzyme systems. For example, copper is a component of the enzymes cytochrome oxidase, uricase, tyrosinase, superoxide dismutase, amine oxidase, lysyl oxidase, and caeruloplasmin.
•  As a component of the enzyme caeruloplasmin (ferroxidase), copper is intimately involved with iron metabolism, and therefore haemoglobin synthesis and red blood cell production and maintenance.
•  Copper is also believed to be necessary for the formation of the pigment melanin and consequently skin pigmentation, for the formation of bone and connective tissue, and for maintaining the integrity of the myelin sheath of nerve fibres.

Dietary sources and absorption: Rich dietary sources of copper include liver, kidney, meat, egg yolk, cereals, nuts and green leafy vegetables. Milk is poor source. Copper is readily absorbed from the gastro-intestinal tract.
Iodine
Biological function:

• Iodine is an integral component of the thyroid hormones, thyroxine and tri-iodo-thyronine, and as such is essential for regulating the metabolic rate of all body processes.

Dietary sources and absorption: Rich dietary sources of iodine include sea foods, drinking water, vegetables, and fruits. Iodine is readily absorbed from the gastro-intestinal tract.

By – Assistant Professor – Mrs. Anita Mehar
Biochemistry Department
Uttaranchal (P.G.) College Of Bio-Medical Sciences & Hospital