Microminerals: they are also called trace elements, they are needed in small amounts within the diet and the quantity is expressed as part

per million (ppm) or milligram (mg).

Microminerals include iron, copper, iodine, manganese, zinc, fluorine, selenium, cobalt, molybdenum, chromium, aluminum, boron and cadmium.

CALCIUM

There are approximately 1000 gm of calcium in the average 70 Kg adult body, of this amount 98% is found in bone, 1% in teeth, and the rest is found in blood, extra-cellular fluids, and within cells where it is a co-factor for a number of enzymes.

Blood calcium:

This is almost confined to the plasma which contains usually 8.5 – 9.5 mg/dl. It is present in three forms:

• A protein-bound calcium (non-diffusible): this fraction is mainly bound to plasma albumin. its concentration is 3 – 4.4 mg/dL.

• Ionized calcium: which is the physiologically active calcium, ranges between 5.5 -6.5 mg/dl.

• Complexed calcium: which is ionized but complexed with citrate, phosphate or other anions, it ranges between 0.15 – 0.51 mg/dL.

Functions of calcium:

1) Calcification of bones.

2) Calcification of teeth, as calcium forms 36% of enamel and 26% of dentine by dry weight.

3) Promotes blood clotting by activating certain coagulation factors.

4) Helps to regulate heart beats, muscle tone and muscle contraction.

5) Plays a role in nerve conduction.

6) Mediator of hormone action.

7) Plays a critical role in apoptosis.

Dietary sources:

The best source of calcium is milk and its products (e.g. cheese, yogurt).

Calcium is also present in vegetables and fruits.

Calcium absorption:

Calcium ions are absorbed mainly in the upper small intestine by an active transport process, which requires the presence of calcium binding protein (CBP).

Dietary factors that reduce calcium absorption are:

● Foods high in oxalic acids (spinach, rhubarb& chocolate) which interfere with calcium absorption by forming insoluble salts.

● Phytic acid or phytates found in whole grain products.

● Excess caffeine, colas or tea.

● Foods rich in fibers.

● Certain medications may reduce absorption of calcium and other minerals.

Dietary factors that increase calcium absorption are:

● Diet rich in proteins increases the solubility and absorption of calcium.

● Acidic foods lower the pH, thus increasing the solubility and absorption of calcium.

Regulation of plasma calcium level:

1) Parathyroid hormone (PTH):

hypocalcemia is the main stimulus for PTH release, PTH increases plasma calcium by the following effects:

● It decreases urinary calcium excretion.

● It increases intestinal absorption of calcium.

● It increases mobilization of calcium and phosphate from bones.

● It activates vitamin D which helps calcium absorption from the intestine.

2) Calcitriol [1,25-(OH)-D3 ] :

This is the active form of vitamin D, it increases intestinal absorption and renal tubular re-absorption of calcium.

3) Calcitonin:

It is secreted by the thyroid gland and helps to lower plasma calcium level.

Requirements:

The recommended dietary allowance (RDA) /day is: 1gm/day for adults, 1.5 gm/day for pregnant and lactating females and 0.5 gm/day for children less than one year.

PHOSPHORUS

Phosphorus has been called the ―master mineral‖ because it is involved in most metabolic processes. Phosphorus, which is stored in bone and teeth, is often discussed in conjunction with calcium.

Calcium : phosphorus ratio is 1:1, too much phosphorus causes poor absorption of calcium.

Blood phosphate:

Plasma inorganic phosphate level is:

- Adults: 3 – 4.5 mg/dL.

- Children: 4 -7 mg/dL.

Functions of phosphorus:

1) Formation of hydroxy-apatite crystals of bone and teeth.

2) It enters in the structure of nucleic acids.

3) It enters in the structure of phospholipids, phosphoproteins and coenzymes.

4) Covalent modification of certain enzymes by phosphorylation and dephosphorylation.

5) Formation of organic phosphorus compounds e.g. G-6-P.

Dietary sources:

It is widely distributed in all foodstuffs, but the best sources are meat and meat organs, milk and milk products.

Absorption:

Phosphorus is absorbed with calcium.

Requirements:

The RDA is similar to calcium.

FLUORINE

In its elemental form, fluorine (chemical symbol F) is a gas. The body uses it in the form of fluoride salts, which are quickly and easily absorbed.

Benefits:

Fluoride is taken into the enamel of teeth, making it harder and more resistant to decay. It exerts its most important effect when the teeth are forming, even before they emerge from the gums. Because of this benefit to teeth, many types of toothpaste contain fluoride, and in some countries, the water supply has fluoride added, to insure that all children receive an adequate supply.

Fluoride prevents dental caries by two mechanisms:

1- Formation of fluoroapatite which is resistant to bacterial attack.

2- Fluoride inhibits the glycolytic enzyme ―enolase‖, thus preventing bacterial fermentation in mouth.

Sources:

Fluoride comes from toothpastes and other dental products to which it has been added. Fluorides also found in fluoridated water, tea, cereals, meat and fish (particularly oily ones as herring, mackerel and sardine).

Deficiency of fluorine:

This is extremely uncommon in humans; fluoride deficiency in animals can stunt the growth, cause hair loss and disorders in the development of teeth.

Overdose or toxicity:

Over-consumption leads to fluorosis, where the teeth become mottled and discolored, and it may also lead to an increase in bone mass and calcification of the ligaments. It may lead to development or exacerbation of arthritis.

Requirements:

RDA is between 1-4 mg.

VITAMINS

●Vitamins are organic nutrients that are required in small quantities for a variety of biochemical functions.

●Vitamins cannot be synthesized by the body and must therefore be supplied by the diet.

● Vitamins do not produce energy nor enter in tissue structure.

●Absence or relative deficiency of vitamins in the diet leads to characteristic diseases.

Classification:

The solubility property was used as a basis for classification of vitamins into: