“Vitamins” summery

Vitamins are a group of organic substances essential in small quantities for normal metabolism. They are found in minute amounts in natural foodstuffs & are sometimes produced synthetically. Deficiencies of vitamins cause specific diseases & disorders.

A. Characteristics: Two characteristics mark a compound to be assigned as a vitamin:

1. It must be a vital organic dietary substance, which is neither a carbohydrate, fat, mineral nor protein, but is necessary in very small quantities to the performance of particular metabolic functions or to the prevention of an associated deficiency disease.
2. It cannot be manufactured by the body & therefore must be supplied in food.

B. Megavitamin Therapy: is the excessive intake of multivitamins to overcome a deficiency in daily requirements. Vitamins in excess of body needs will be excreted.

C. Classification of Vitamins: Vitamins are usually grouped according to their solubility:

1. The fat-soluble group includes vitamins A, D, E & K.
2. The water-soluble group includes vitamin C & the B‑Complex vitamins.

I. Fat Soluble Vitamins

Absorption of fat soluble vitamins depends upon:

• Presence of fats in the GIT.
• Hepatic function.
• Bile contents.

A. Vitamin A (Retinol): Vitamin A is an alcohol & because it has a specific function in the retina of the eye, it has been given the name Retinol. However, it is still commonly referred to as vitamin A.        b-carotene (pro-vitamin A) is the precursor of vitamin A.

b-carotene  ^metabolism   Retinol (Vitamin A)  ^metabolism      11-cis-retinol

                                                            Rhodopsin                                          Iodopsin

                                    (Retinal rod cell pigmentation)                       (Retinal cone cell pigmentation)

                                    It is photosensitive & essential

                                    for dark adaptation

1. Physiologic functions of vitamin A:

• Vision: Vitamin A is necessary for the proper functioning of some inner parts of the eye that are concerned with night vision.
• Epithelial Tissue: Vitamin A has an important role in the formation & maintenance of healthy, functioning epithelial tissue, the body’s 1^ry barrier to infections.
• Growth: It has been observed that vitamin A deficiency is associated with retarded growth (mechanism unknown). Vitamin A is essential for the growth of skeletal, soft tissues, bones & teeth.

 

2. Hypovitaminosis “A”: A deficiency in vitamin A may occur for 3 basic reasons:

• Inadequate dietary intake.
• Poor absorption.
• Inadequate conversion of carotene (liver or intestinal disease).

This deficiency can lead to:

• Night blindness: a condition known as nyctalopia.
• Xerophthalmia
• Keratinization of epithelial cells of the cornea of the eye.
• Keratinization of epithelial cells, these become dry, flat, & gradually harden to form scales that will peel off; leading to infection.
• Loss of appetite.

3. Hypervitaminosis “A”: Vitamins are substances required in small amounts, & too much of some vitamins can be dangerous. Since the liver has a great storage capacity for vitamin A, megadoses of this vitamin are toxic. Hypervitaminosis A is manifested by: joint pain, thickening of long bones, loss of hair, & jaundice.

In children: hyperstoses (bone hypertrophy)

In adults & children:

Peeling of skin Headache Lymph node enlargement Nystagmus

4. Food sources of vitamin A:

• Animal sources: fish‑liver oil, liver, kidney, milk, butter & egg yolk,
• Plant sources: are the yellow & green vegetables & fruit sources of carotene; e.g. carrots, sweet potatoes, apricots, spinach & cabbage.

5. Uses of vitamin A:

Psoriasis. Acne vulgaris. Ichllryosis (dark area on the skin) Night blindness.

6. Daily requirements: Vitamin A can be taken orally or IM. 

• Daily requirements in children:           1300 IU – 2600 IU
• Daily requirements in adults:              3000 IU

Any preparation containing vitamin A should contain not less than 1,600 IU for adults and 1,000 IU for children. Additionally, it should not exceed 10,000 IU.

One IU vitamin A = the biological activity of 0.3 mg of retinol or 0.6 mg of carotene.

Zinc (Zn) 8-9 mg/day is essential for:

• Maintenance of vitamin A in plasma.
• Mobilization of vitamin A from the liver.

Administration of a small amount of vitamin E with vitamin A will increase the absorption & tissue storage of vitamin A, & protect against the oxidation of vitamin A (available as vitamin A+E).

Vitamin A does not pass the placenta.

B. Vitamin D (Calciferol): Vitamin D is unique among the vitamins in two respects:

• It occurs naturally in only a few common foods (mainly fish oil & a little in egg & milk).
• It can be formed in the body by exposure of the skin to UV rays either from the sun or a lamp.

7-hydroxy ergosterol         ^{UV / activation in the liver}   Cholicalciferol (vitamin D₃) (natural)

Ergosterol                                ^UV                                           Calciferol (vitamin D₂) (synthetic)

Cholicalciferol is 100 times as active as ergocalciferol.

1. Physiologic function of vitamin D: Vitamin D has hormone‑like (para-hormone) functions closely inter-balanced with the parathyroid hormone in calcium & phosphorus metabolism. 

• Absorption of calcium & phosphorus from the small intestine.
• Calcification: Vitamin D works with calcium & phosphorus in the calcification aspect of bone formation. It increases the mobilization of Ca⁺⁺ from blood to bones.
• Increases tubular reabsorption of Ca⁺⁺.

2. Hypovitaminosis “‘D”: can happen due to inadequate exposure to sunlight (UV) &/or dietary deficiency. This can lead to:

• Rickets (in children): a disease directly related to impaired metabolism of Ca & P, due to vitamin D deficiency. Characteristic clinical manifestations of rickets result from failure of calcification of growing bones. Several deformities of bones develop e.g. softening of cranial bones, bowed thighs & knock‑knees. 
• Osteomalacia (soft bones): in adults.
• Hypo-parathyrodism: in adults.

3. Hypervitaminosis “‘D”: ingestion of excessive quantities of vitamin D can produce toxicity. Symptoms of vitamin D toxicity are:

• Calcification of soft tissues such as lungs & kidney (kidney stones).
• Hyper-calcemia (increased Ca⁺⁺ levels in blood).
• Bone fragility.
• Increased digitalis toxicity.
• Mental retardation.
• MI.

4. Food sources of vitamin “D”: The 2 basic food sources are yeast & fish liver oils. The main food sources are those to which vitamin D has been added or produced by irradiation, especially milk.

Vitamin D is completely absorbed from the GIT. Absorption depends on hepatic & biliary functions. Drugs that increase hepatic microsomal enzymes (anti-coagulants, barbiturates, rifampicin & anti-depressants) lead to increased elimination of vitamin D and may cause its deficiency.

5. Uses of vitamin D:

• Anti-rickettic: in children (it promotes calcification of organic matrix of bone structure).
• Treatment of hypo-parathyrodism.

6. Daily requirements: 400 IU / day.

One IU vitamin D = 0.025 mg vitamin D₂.

Lasix (frusemide) is contraindicated in vitamin D deficiency as lasix itself is a hypo-calcemic agent.

C. Vitamin E (a-Tocopherol): is known as the antisterility vitamin, but it has been demonstrated to have this effect only in the rat & not in man.

1. Physiologic function of vitamin E: because of its reducing properties, Vitamin E protects the body against peroxides that can destroy capillary walls & RBCs; it has several physiologic functions including: 

• Anemia: The evidence of the role of vitamin E in erythrocyte protection has led to further inquiry into possible relationship between this vitamin & blood disorders.
• Muscular System: Vitamin E plays a role in the normal development of muscles.
• Vascular System: Vitamin E is necessary for normal resistance of erythrocytes to hemolysis.

2. Hypovitaminosis “E”:

Deficiency anemia. Muscular dystrophy. Male sterility. Habitual abortions in females.

3. Hypervitaminosis “E”: Vitamin E is a safe drug that can be given in large doses. 

4. Food sources of vitamin E: Richest sources are vegetables & seed oils. Others: milk, eggs, meat, fish. 

5. Uses of vitamin E: Vitamin E is used to increases absorption of vitamin A. Additionally, because of its reducing properties, it is used in commercial products (oily solutions) to prevent spoilage, & is added to therapeutic forms of vitamin A to prevent oxidation.

6. Daily requirements:            5 – 10 IU

Vitamin E is carried in the plasma by b-lipoproteins. It is incompatible with minerals e.g. Fe³⁺ & Ca²⁺

D. Vitamin K: is a group of fat-soluble vitamins that promote blood clotting. It is synthesized by the normal intestinal bacteria so that an adequate supply is generally present.

It is a naphtoquinon derivative that exists in 3 forms:

• Vitamin K₁ (phytoquinon):     of plant origin.
• Vitamin K₂ (menaquinon):      of bacterial origin (in the GIT).
• Vitamin K₃ (menadion):          Synthetic, waer soluble (inactive).

1. Physiologic functions of vitamin K: The major function of vitamin K is to increase the hepatic synthesis of prothrombin. Prothrombin is an essential factor in blood coagulation. 

2. Hypovitaminosis “K”:

• Rarely occurs & is manifested by increased prothrombin time, and hemorrhagic tendencies.
• Excessive use of oral antibiotics can inhibit the normal GIT flora responsible for synthesis of vitamin K and might lead to its deficiency.

3. Hypervitaminosis “K”:

• In infants: hemorrhagic anemia, kernicterus, & increased bilirubin.
• In adults: decreased liver functions leading to jaundice.
• Caumarine (dicaumarol) is the antidote for vitamin K toxicity.

4. Food sources of vitamin K: Green leafy vegetables (cabbage, spinach), cheese, egg yolk & liver.

5. Daily requirements: No requirement for vitamin K is stated since adequate amount is usually ensured through intestinal bacteria & the body requires vitamin K in very small amounts. 

II. Water Soluble Vitamins

A. Vitamin C (Ascorbic Acid):

1. Physiological functions of vitamin C:

• Building & maintaining bone matrix, cartilage, collagen & connective tissue. Its deficiency has long been associated with the hemorrhagic disease “‘Scurvy”.
• Vitamin C helps in the absorption of iron from the GIT.
• It is important in oxidation – reduction (redox) reactions in the body & for cellular respiration.

2. Deficiency of vitamin C: Scurvy is the nutritional disease associated directly with vitamin C deficiency. Tissue deterioration & changes of hemorrhagic origin take place. The skin becomes dry, rough & has a brown color. Hemorrhages occur in the gums, muscle tissue & in the cavities of joints, causing infants in particular to lie, in the “pithed frog” position. Lesions in teeth, bones & blood vessels.

3. Vitamin C toxicity:

• Increased stone formation in the urinary tract.
• Diarrhea
• Ingestion of 10 gm daily of vitamin C followed by rapid withdrawal causes frank symptoms of scurvy. Similarly, scurvy develops in newborns to mothers who suddenly stop ingesting large daily doses of vitamin C.

4. Food sources of vitamin C: Citrus fruits & tomatoes are well known sources of vitamin C. Other sources include cabbage, potatoes as well as green & yellow vegetables.

5. Uses of vitamin C

• Wound healing: The important role of vitamin C in cementing supportive tissue makes it an important agent in wound healing. This has evident importance for vitamin C therapy in surgery or burns especially where extensive tissue regeneration is involved.
• Fevers & infections: infections, especially bacterial infections, decrease tissue stores of vitamin C, & additional intake is required to help maintain resistance to infection.
• Reaction to Stress: Any body stress such as fracture, general illness & shock requires vitamin C.
• Treatment of mega-hemoglobinemia: because of its reducing properties.
• Antidote for alcohol over dosage: as it activates the alcohol dehydrogenase enzyme which is essential for alcohol metabolism.

6. Daily requirements:

• Children:         > 20 mg / day
• Adults:                        > 150 mg / day

Women have higher vitamin C levels than men.

Smoking reduces vitamin C levels in blood.

Vitamin C (like other reducing agents e.g. ampicillins) gives false positive results with clintest. The test depends on the reduction of CuSO₄ by glucose in urine. Thus, the testape method can be used instead.

B. Vitamin B₁ (Thiamine): is the anti-beriberi factor & is an essential co-enzyme in carbohydrate metabolism (2 carbo atom metabolism, getting rid of pyruvic acid). If Thiamine is not present in sufficient amounts, clinical effects will be reflected in the GI, CV, & nervous system.

1. Deficiency of vitamin B₁: causes beriberi. The disease results from the consumption of white wheat, polished rice & alcoholics. The 2 general types of beriberi are infantile & adult. It is characterized by convulsive disorders, respiratory difficulties & GI problems (constipation & vomiting). Symptoms include:

Peripheral neuritis Mental disorders Fatigue Decreased conc. of HCl Tachycardia Cardiac hypertrophy Cardiac failure

2. Toxicity of vitamin B₁: because vitamin B₁ is very safe, toxicity is not marked.

3. Food sources of thiamine: beef, liver, whole or enriched grains, bran, yeast, eggs & fish. However, vitamin B₁ is thermolabile.

4. Uses of vitamin B₁: Vitamin B₁ is useful in the treatment of

Beriberi. Peripheral neuritis in diabetic patients. Neuralgia (nerve inflammation). Mental disorders.

Vitamin B₁ may be administered orally, or by subcutaneous or IM injection.

5. Daily requirements:

Adults:                        > 0.6 mg (4.5 mg) Children:         > 0.4 mg

 

C. Vitamin B₂ (Riboflavin): is a yellow‑green fluorescent pigment that is found in milk. It is an important factor in protein metabolism (it acts as a proton carrier).

1. Vitamin B₂ deficiency:

• Riboflavin deficiency chiefly causes tissue inflammation & breakdown.
• Wounds become easily aggravated.
• Lips & nose crack easily (chelosis – cracks in the corner of the mouth)
• Glossitis (inflammation of the tongue)
• Seborrheic dermatitis (scaly, greasy eruption of the skin), Keratitis
• Photophobia due to corneal vascularization.
• Toxicity of the embryo in pregnants.
• Riboflavin deficiencies seldom occur alone, they are especially likely to occur in conjunction with deficiencies of other B vitamins & protein.

2. Food sources of riboflavin: Most important food sources are milk. Other good sources are liver, kidney & some vegetables. It is absorbed from the upper GIT.

3. Daily requirements:

Adults:            > 1 mg Children:        > 0.6 mg

Vitamin B₁ may be administered orally, or by subcutaneous or IM injection. It is never given alone but rather in combination with other B vitamins.

D. Vitamin B₃ (Niacin, Nicotinic Acid)

• Vitamin B₃ occurs either as Nicotinic acid or Nicotinamide.

CONH2

N

COOH

N

 

Nicotinic acid                                      Nicotinamide

1. Physiological functions of vitamin B₃:

• Niacin is an important factor in the metabolism of proteins, fats & glucose. It acts as a H⁺ carrier co-enzyme and for the production of ATP (in the respiratory chain).
• Niacin and riboflavin are closely interrelated in cell metabolism. And if one of these vitamins is deficient, the other is usually deficient as well.

2. Vitamin B₃ deficiency:

• The disease associated with niacin deficiency is “pellagra” which is characterized by a typical dermatitis & often has fatal effects on the nervous system.
• The deficiency is manifested as:
  • Weakness, lassitude,
  • GIT effects including anorexia & indigestion.
  • If deficiency continues, the skin & nervous system will be affected. The skin areas exposed to sunlight develop a dark, scaly dermatitis (photosensitivity). Neuritis, confusion, apathy, schizophrenia & disorientation also develop.

3. Vitamin B₃ toxicity:

Flushing Vasodilatation   Hepatotoxicity   GIT irritation & ulceration

Other side effects of vitamin B₃ include:

• Hyperuricemia
• Glucose intolerance (hyperglycemia)

4. Uses of vitamin B₃:

• Treatment of pellagra.
• Nicotinic acid (but not nicotinamide) in doses of > 3 gm / day, is hypocholesterolemic.

5. Food sources of niacin: Meat is the major source of niacin. Peanuts, beans & peas are good sources.

6. Daily requirements:

• Adults:            > 6 mg – 45 mg
• Children:        > 4 mg

60 mg of tryptophan = 1 mg of nicotinic acid (niacine).

N.B: When vasodilatation is contraindicated we can use nicotinamide instead of nicotinic acid.

E. Vitamin B₆ (Pyridoxine):

1. Physiological functions of vitamin B₆:

• Vitamin B₆ acts as a coenzyme in protein (amino acid) metabolism (in decarboxylation & transamination).
• It is essential for the production of GABA (gamma-amino-butyric-acid) in the brain which is the main neurotransmitter inhibitor to prevent convulsions.

Serotonin (5HT)  ^decarboxy.    Tryptophan        ^{Pyridoxal 6 phosphate coenzyme}            Nicotenic acid

2. Pyridoxine deficiency: Since pyridoxine plays an important role in several metabolic activities, it’s deficiency may cause the following problems:

• Anemia: Hypochromic, microcytic anemia has been observed in several patients even in the presence of high serum iron levels.
• Central Nervous System Disturbances: epileptic convulsions & peripheral neuritis.
• Pregnancy & Estrogen-­progesterone Oral Contraceptives deplete vitamin B₆ & thus require additional vitamin B₆.
• INH, Hydralazine & Penicillamine: decrease the tryptophan metabolism & lead to vitamin B6 deficiency.

3. Food sources of pyridoxine: Yeast, wheat, corn, liver & kidney are good sources of vitamin B₆.

There is evidence that intestinal bacteria produce this vitamin, but the full extent of this source & the degree to which it is utilized by the body are not yet determined.

N.B: Vitamin B₆ is contraindicated with L-dopa as it increases its metabolism through increasing the synthesis of the decarboxylase enzyme, which converts L-dopa to dopamine in the peripheral tissues before entering the brain.

Pyridoxal is more stable than pyridoxine.

F. Pantothenic Acid (Panthenol):

• Pantothenic acid is available in all forms of living things & throughout body tissues.
• Intestinal bacteria synthesize considerable amounts of pantothenic acid. This, together with its widespread natural occurrence, makes deficiency unlikely.
• Pantothenic acid plays a vital coenzyme role in overall body metabolism. It is converted to co-enzyme A which is essential for the synthesis of acetylcholine & in fatty acid metabolism.

1. Food sources of pantothenic acid: Yeast, liver & kidney are rich sources, followed by egg, especially the yolk, leafy vegetables & skimmed milk.

2. Uses of pantothenic acid:

• It is used locally to aid wound healing.
• It can be given IM to aid motility of the intestine after surgical operations i.e. to guard against post-operative paralytic ileus.

G. Vitamin B₁₂ (Cyanocobolamin): In 1948 vitamin B₁₂ was discovered & was shown to have control over the blood‑forming defects & neurologic problems involved in pernicious anemia.

1. Physiologic function of vitamin B₁₂:

• Haematopoiesis: A well-established role of vitamin B₁₂ is it participation in the formation of RBCs, & therefore, in the control of pernicious anemia.
• Maintenance of the myelin sheath of the nervous tissue: its deficiency leads to neurologic signs.
• Production & normal growth of epithelial cells: in the GIT mucosa, cervix, vagina & tongue.

2. Deficiency of vitamin B₁₂: Leads to perinaceous anemia (macrocytic &/or megaloplastic anemia), which affects all highly proliferating cells & is characterized by:

• RBCs large sized
• WBCs with polysegmented nucleus
• Platelets are giant
• Bone marrow with large cells

3. Uses of vitamin B₁₂:

• Treatment of perinaceous anemia (Addison’s perinaceous anemia) which is a disease resulting from the vitamin B₁₂ deficiency. This deficiency can be either due to low vitamin B₁₂ levels, or defective vitamin B₁₂ absorption due to deficiency of the GIT intrinsic factor.* Symptoms include peripheral neuritis, gastric mucosal atrophy, glotitis, achlorohydria (lack of HCl secretions), & megaloplastic anemia.
• The drug of choice for the treatment of perinaceous anemia is vitamin B₁₂ given by IM or subcutaneous injection (oral B₁₂ is of no value as it will not be absorbed due to lack of intrinsic factor). Folic acid should not be given as it can mask the symptoms of perinaceous anemia.
• Vitamin B₁₂ injection is available as 100 mg or 1000 mg/ml e.g. depovit (1000 mg B₁₂ + Zn acetate + tannic acid suspension)
• Sprue: Like folic acid, vitamin B₁₂ was effective in treating sprue. However, it seems most effective when used in conjunction with folic acid.

4. Food sources of vitamin B₁₂: Vitamin B₁₂ is supplied almost entirely by animal foods where it is stored in organ meat. The richest sources are liver, kidney, meat, milk, eggs & cheese. 1ml of liver extract = 10 mg of vitamin B₁₂.

It is the only nutrient that needs a gastric secretion (intrinsic factor) to be absorbed from the GIT. The intrinsic factor is glycoprotein in nature & is secreted by the parital cells of the stomach (that secrete HCl).

This glycoprotein forms a complex with vitamin B₁₂. The ilial cells take up the formed complex transporting it to the blood where plasma b-globine transfer it to cobolamine II.

Intestinal bacteria also synthesizes some vitamin B₁₂ although the amount supplied is not known.

* Shilling test is used to differentiate whether the cause of perinaceous anemia is vitamin B₁₂ defficiency or deficiency in both  vitamin B₁₂ & the intrensic factor. Radioactive (Co⁵⁷ or Co⁵⁸) vitamin B₁₂ is given orally. If perinaceous anemia is due to both (intrensic factor & vitamin B₁₂ deficiency) then vitamin B₁₂ will not be absorbed & Co appears in the feaces in large amounts. If Co appears in the urine (i.e. vitamin B₁₂ was absorbed) then the anemia was due to defficiency in vitamin B₁₂ only.

H. Folic Acid (B₉): belongs to group B‑vitamins that have an important role in cell growth & blood­-forming factors.

1. Physiologic function of folic acid:

• Folic acid is essential for the synthesis of purine & pyrimidine nucleotides.

Folic acid  ^{folate reductase enzyme}  tetra-hydro folinic acid    ^{synthesis reaction}  purine + pyrimidine

(puroyl glutamic acid)

2. Deficiency of folic acid:

• Anemia: Simple folic acid deficiency can cause nutritional megaloblastic haematopiosis, a condition that differs from megaloplastic anemia caused by vitamin B₁₂ deficiency in lacking the neurologic symptoms, i.e. no myelin damage. (Folic acid is not fully effective as a specific agent in the control of pernicious anemia).*
• Sprue: Folic acid is effective in treating sprue, a GI disease characterized by severe diarrhea.

3. Toxicity of folic acid: Folic acid is not toxic by the oral route.

4. Food sources of folic acid: Liver, kidney & fresh green leafy vegetables are rich sources.

5. Uses of folic acid:

• Folic acid is used to treat nutritional megaloblastic haematopiosis
• It is also used, in comination with vitamin B12 to treat megaloplastic anemia.
• A metabolite of folic acid, methotroxate, is used to treat cancer, psoriasis and rheumatoid arthritis.

6. Daily requirements:            50 mg / day

* Folic acid can mask the signs of perinaceous anemia but will not prevent the progression nor the neurologic symptoms.

I. BIOTIN: is a member of the B‑Complex group of vitamins. It has been called a “micronutrient” because such minute traces of it perform its metabolic task.

• It is synthesized by the intestinal flora or taken with ingested food.
• It has a high potency & a natural deficiency is unknown.
• Biotin is a coenzyme in carbon dioxide reactions in energy metabolism. It is involved in fatty acid synthesis & in many carboxylation reactions.

1. Food sources of biotin: excellent food sources include egg yolk, liver, kidney, tomatoes & yeast. Large amounts of egg white causes its deficiency.

 

J- Choline:

• It is synthesized in the body from the amino acid methionine.
• It is essential for the synthesis of phosphatidyl-choline which is involved in lipid transport & acetylcholine synthesis

Minerals

I- Definition: Minerals are inorganic elements widely distributed in nature, & many of them have vital roles in metabolism. Minerals may be grouped according to their amount in the human body.

• Major Minerals: These are present in large amounts, in the human body. Calcium, sodium, potassium, magnesium, phosphorus, sulfur and chlorine belong to this group.
• Trace Minerals: These are present in small amounts & have a known function. This group includes iron, copper, iodine, manganese, cobalt, zinc & molybdenum.
• Trace Minerals (function unknown): This group includes minerals whose function in the body is unknown, such as selenium, chromium, nickel & silicon.

II- Major Minerals

A- Calcium:

• Of all the minerals in the human body calcium is present in by far the largest amounts.
• It comprises 1.5 – 2.0 % of the total body weight. 99 % of this mineral is in skeletal tissue (bones & teeth) as deposits of calcium salts.
• The remaining 1% of body calcium performs highly important metabolic tasks & it occurs in the plasma & other body fluids.

1. Physiologic function of calcium:

• Bone & teeth formation.
• Blood clotting.
• Muscle contraction & relaxation: Ca plays an important role in the initiation of muscle contraction. This is particularly important in the contraction ‑ relaxation cycle of the heart muscle.
• Nerve transmission: calcium is required for the normal transmission of nerve impulses.
• Cell wall permeability: ionized calcium controls the passage of fluid through cell walls by affecting cell wall permeability.
• Enzyme activation.

2. Clinical application:

Tetany: A decrease in ionized serum calcium causes tetany, a state marked by severe, intermittent spastic contractions of the muscle & by muscular pain. It is manifested by a characteristic spasm of the muscles in the upper extremity, which causes flexion of wrist & thumb with extension of the fingers.

Rickets: deficiencies in salcium, phosphorus &/or vitamin D are all related to rickets. When adequate. calcium & phosphorus are not absorbed, proper bone formation cannot take place.

Renal Calculi: The majority of renal stones are composed of calcium. Immobilization of the body through a cast or other orthopedic device causes an increase in the amount of calcium excreted in urine. Hyperparathyrodism &hypoparathyroidism: Because calcium & phosphorus metabolism are so directly controlled by parathyroid hormone, conditions of the parathyroid gland that increase or decrease the secretion of its hormone will immediately be reflected in abnormal metabolism of these 2 minerals.

As such, dietary calcium intake should be adequate and should not exceed the usual daily allowances.

3. Food sources of calcium: Dairy products supply the bulk of dietary calcium. Secondary sources such as egg yolk, green leafy vegetables, legumes & nuts contribute much smaller quantities.

B. Phosphorus:

• Phosphorus is closely associated with calcium & both occur in the same major food source ‑ milk.
• Both play major roles in bone building & are related to vitamin D in their absorption process. Both are regulated metabolically by parathyroid hormone, & exist in blood in definite ratio to another.
• In addition to these functions related to calcium, phosphorus has other unique physiological functions that are of clinical importance. These include:
  • Growth: Growing children usually have high serum phosphate levels, probably resulting from high levels of growth hormone.
  • State of Recovery from Diabetic Acidosis: results in active carbohydrate absorption & metabolism that increases the use of phosphorus, resulting in temporary hypophosphatemia.

1. Changes in serum phosphorus level: Situations of pathologic changes in serum P level include:

Hypophosphatemia: Intestinal diseases as sprue & celiac disease in which P absorption is hindered or bone disease as rickets in which the Ca : P balance is upset, are characterized by low serum P levels.

The serum phosphorus level is also low in primary Hyperparathyrodism, because the excess quantity of parathyroid hormone secreted results in excessive renal excretion of phosphorus.

Symptoms of hypophosphatemia include muscle weakness, because the muscle cells are deprived of phosphorus essential for energy metabolism.

Hyperphosphatemia: Renal insufficiency or hypoparathyroidism causes excess accumulation of serum phosphate. As a result, the calcium side of the Ca : P ratio is low, which causes Tetany.

2. Food sources of phosphorus:

Milk & milk products are the most significant sources of phosphorus. Meat is also a good source.

C. Magnesium:

• Magnesium, an essential nutrient, occurs in the body in considerable quantities.
• There are ~ 25mg in an adult & 70 % of this is combined with Ca & P in the bone‑salts complex.
• The remaining 30% is distributed in various soft tissues & body fluids.
• Ionized magnesium is essential to cellular metabolism of both carbohydrate & protein.
• It is also related to cortisone in the regulation of the blood phosphorus level.
• Decreased ionized magnesium levels causes vasodilatation & inhibits smooth muscle action, & causes neuromuscular irritability.
• A tetany‑like syndrome has been observed in animals fed a low magnesium diet.

1. Clinical application:

GIT disorders: In prolonged diarrhea or vomiting or in diseases characterized by GIT mal-absorption, excessive amounts of Mg may be lost. Fundamental to the treatment of such states is re-hydration that must be accompanied by adequate Mg replacement, if it is not, the low serum Mg level may give rise to neuromuscular irritability, manifested by tremor, spasm, & increased startle response to sound & touch.

Alcoholism: A Tetany‑like syndrome has been studied in persons with chronic alcoholism in whom magnesium deficiency has developed.

2. Food sources of magnesium: Mg is relatively widespread in nature. Its main sources include: nuts, soybeans, cocoa, seafood, whole grains and dried beans.

D. Sodium:

• Sodium crucially important to many metabolic activities, is one of the more plentiful minerals in the body.
• About 1/3 of Na is present in the skeleton as inorganic bound material; the remaining 2/3 is in extra‑ cellular fluids.
• It plays a major role in maintenance of fluid & acid‑base balance in the body & normal muscle irritability.

Food sources of sodium: Common salt, is the main dietary source of sodium.

E. Potassium

• Like sodium, potassium is a vital mineral element associated with physiologic fluid balance.
• It is the major caution of the intracellular fluid.
• However, the relatively small amount in extracellular fluid as a significant effect on muscle activity, especially heart muscle.
• Small variations in the serum potassium concentration are reflected in electrocardiograph changes.

1. Clinical application:

Hyperkalemia (elevated serum potassium): A rise in serum potassium results in weakening of heart action, mental confusion, poor respiration, & numbness of extremities.

Hypokalemia (low serum potassium): Hypokalemia of dangerous degrees may be caused by a prolonged wasting disease with tissue destruction & malnutrition, or by prolonged GI loss of K as in diarrhea or vomiting. Additionally, the continuous use of certain diuretic drugs, as HCTZ increases K excretion.

To prevent complications of cardiac failure, K should be given, especially when K depleting diuretics are used.

2. Food sources of potassium:

• K is widely distributed in natural foods. Grains, leafy vegetables & meat supply considerable amounts.

F. Chlorine

• Chlorine occurs in the body as the chloride ion (CI).
• It is the major anion in the extracellular fluid, & its highest concentration is in the CSF.
• Together with ionized Na, ionized Cl in the extracellular fluid helps to maintain water balance & to regulate osmotic pressure.

1. Food sources of chlorine:

• Almost the only dietary source of Cl is a partner to Na in table salt.

 

III- Trace Mineral with Known Function

A. Iron

Iron is distributed in the body in 4 main forms that point to its basic metabolic functions.

• Transport iron: A very small amount of iron is found in the plasma. This iron is being transferred from one point of use to another by binding with a protein ‑ transferrin.
• Hemoglobin: About 75 % of the body’s iron is in hemoglobin, that is found in RBCs which is responsible for O₂ transport to the cells for respiration & metabolism.
• Storage Iron: Around 20 % of body iron is stored in the liver, spleen & marrow as the protein‑iron compound ferritin.
• Cellular Tissue Iron: About 5 % of total body iron is distributed throughout the cells as a major component of the enzyme system responsible for production of energy.

1. Iron deficiency:

Anemia results from either a lack of iron or inability to use it by the body due to one of several causes:

• Inadequate supply of iron in the diet ‑ nutritional anemia.
• Excessive blood iron loss ‑ hemorrhagic anemia.
• Inability to form hemoglobin in the absence of other necessary factors such as vitamin B₁₂
• Lack of gastric HCl necessary to liberate iron for absorption.

2. Food sources of iron:

• Organ meats, especially liver, are by far the best sources of iron.
  • Other food sources include meats, egg yolk, & seafood.

B. Copper

• Broadly speaking, copper seems to behave in the body as a companion to iron.
• The two are metabolized in much the same way & share some functions.
• Copper is additionally involved in two other areas of metabolism:
  • Bone formation.
  • Brain tissue formation and maintenance of the nervous system.

Food sources of copper:

• Cu is widely distributed in natural foods &, given a sufficient caloric intake, Cu will be amply supplied.

C. Iodine

• Iodine is a trace element associated mainly with the thyroid gland.
• It participates in the synthesis of the thyroid hormone.
• This is the only known function of iodine in human metabolism.
• Deficiency of iodine will cause goiter characterized by great enlargement of thyroid gland plate.

Food sources of iodine:

• Commercial iodized table salt provides the main dietary source of iodine,
• Seafood also provides a considerable amount of iodine.

D. Manganese

• In nutrition, traces of manganese serve as essential activating agents that strengthen & stimulate a number of vital metabolic reactions.

Food sources of manganese:

• The best food sources of manganese are of plant origin: cereal bran, soybeans, legumes, nuts, tea & coffee.

E. Zinc

• Zinc occurs in the human body in amounts larger than those of other trace elements except iron.
• It functions mainly as an essential constituent of several enzymes mainly a CO₂ carrier in RBCs.
• Zinc also combines readily with insulin in the pancreas.

1. Clinical application:

• Hypogonadism & dwarfism from pronounced human zinc deficiency during growth periods has been recognized.
• Wound healing is also related to zinc intake. According to recent studies, zinc‑deficient wounds seem to be common in the average hospital, and patients benefit from zinc supplementation.

2. Food sources of zinc: Best food sources of zinc are seafood, meat and eggs.

F. Molybdenum

• Amounts of molybdenum in the body are very minute.
• This trace mineral is present in bound form as an integral part of various enzyme molecules & facilitates the action of the specific enzyme involved.
• In addition molybdenum is interrelated with copper metabolism.
• It may also exert a beneficial effect upon the incidence & severity of dental caries & may enhance the well‑established effect of fluoride.

Food source of molybdenum: whole grains milk, leafy vegetables & organ meats.

 

 

IV. Trace Minerals with Unknown Functions

A. Selenium

• Within the last 15 years, selenium has been recognized to be an essential nutrient element in certain species, & its function as a component of several enzymes has been identified.
• It was observed that selenium containing compounds protect the liver against fatty infiltration & necrosis.
• This action of selenium may be related to that of Vitamin E, since the 2 substances appear to act together in curing the hepatic disease.

Food Sources of Selenium: seafood, meat and whole grains.

B. Chromium

• The human body contains less than 6mg of chromium.
• Chromium may affect lipid metabolism as well as carbohydrate metabolism; studies have shown that chromium can raise abnormally low fasting blood sugar levels & can improve faulty uptake of sugar by body tissues.
• Physicians working in Jerusalem with refugee infants suffering from severe malnutrition & an inability to use sugar found that when small amounts of chromium were added to their diet, the infants made rapid recovery.
• It has been speculated that chromium may have a possible link with chronic disease processes such as CV disorders & diabetes.

Food sources of Chromium: Best food source is meat and whole grains.