Vitamins

Definition of Vitamin Vitamins are chemically unrelated organic compound that cannot be synthesized by humans and ,therefore, must be supplied by the diet. Vitamins = vita (life) + (amines)

Ascorbic acid (vitamin C) Non-B-Complex Ascorbic acid (vitamin C) The active form of vitamin C is ascorbic acid. The main function of ascorbic acid is as a reducing agent in several reducing agent in several different reaction. Its required for the maintenance of normal connective tissue as well as for wound healing . Its also facilitates the absorption of dietary iron from the intestine. Its highest concentration is in the adrenal cortex and eyes , its easily destroyed by heat and alkalis , discovered in 1928 .

Deficiency of ascorbic acid A deficiency of ascorbic acid results in scurvy , a disease characterized by sore, spongy gums, loose teeth, fragile blood vessels, swollen joints and anemia. A decrease of body resistance to infections. A decrease of amino acid metabolism.

- Occurrence : vit. C is best obtained from : citrus fruits ,tomatoes , peppers, spinach, liver,fish,and milk. RDA: varies according to age, sex and individual conditions and normally its about 35 mg. /day in infants , 45 mg./day in adults .This quantity must be increased into 60 mg./day for pregnant and nursing women.

B-complex Folic acid Folic acid or folate plays a key role in one - carbon metabolism. is essential for the biosynthesis of several compounds. - Function of folic acid : tetrahydrofolate receives one – carbon fragment from doners such as serine, glycine, and histidine and transfer them to intermediates in the synthesis of amino acids, purines and pyrimidine found in DNA.

Nutritional anemias Anemia: is a condition in which the blood has a lower than normal concentration of hemoglobin which results in a reduced ability to transport oxygen. Nutritional anemia: are conditions caused by inadequate intake of one or more essential nutrients. Folate and anemia : Inadequate serum levels of folate can be caused by increased in pregnancy and lactation , poor absorption caused by pathology of small intestine, alcoholism oe treatment with drugs tat are dihydrofolate reductase inhibitors. Megaloblastic anemia: a primary result of folic acid deficiency lead to …………..…

Folate and neural tube defects in the fetus Spina bifida and anencephaly are the most common neural tube defects : Spina bifida is a birth defect in which there is incomplete closing of the spine and membranes around the spinal cord during early development. There are three main types: spina bifida occulta, meningocele and myelomeningocele.The most common location is the lower back, but in rare cases it may be the middle back or neck.

Anencephaly is the absence of a major portion of the brain, skull, and scalp that occurs during embryonic development.

Cobalamin (vitamin B12) Vitamin B12 is requried in humans for two essential enzymatic reactions:

Structure of cobalamin and its coenzyme forms

Clinical indication for vitamin B12 vitamin B12deficiency is rarely a result of an absence of the vitamin in the diet. It is much more common to find deficiencies in patients who fail to absorb the vitamin from the intestine resulting in pernicious anemia .

Thiamin (Vitamin B1) Thiamine pyrophosphate TPP is the biologically active form of the vitamin .formed by the transfer of a pyrophosphate group from ATP to thiamine.

Clinical indications for thiamine Transketolase , pyruvate dehydrogenase and α-ketoglutarate dehydrogenase.

- Beriberi : this is a sever thiamine deficiency syndrome found in areas where polished rice is the major component of the diet. Sings include tachycardia , vomiting , dry skin , disorderly thinking and progressive paralysis. Wernicke- Korsakoff syndrome : is due to dietary insufficiency or impaired intestinal absorption of the vitamin. It is seen primarily association with chronic alcoholism . a deficiency state characterized by apathy loss of memory and a rhythmical to and fro motion of the eyeballs.

-Occurrence: Its found principally in un-refined cereals ,liver ,heart ,beef ,nuts ,eggs and fish . - RDA :varies according to age ,sex,activity.pregnancy, lactation and the type of diet [carbohydrates] .Normally its about 1 --- 1.5 mg./day

Vitamin B2 vit. B2 is an orange-yellow crystalline compound soluble in water ,stable to heat and discovered in 1933 .

-Occurrence : riboflavin is found mainly in: meat ,milk ,wheat ,kidney ,barley and corn . -RDA : varies according to age,sex ,individual conditions and normally its about 0.4-1.8 mg./day

Niacin (Vitamin B3) Niacin or nicotinic acid

-Occurrence : vit.B3 is found mainly in : liver ,kidney ,meat ,milk ,yeast ,vegetables and cereals . - deficiency of vit.B3 is mainly characterized by : Dermatitis ,Diarrhea, and Dementia so its known as a vit. Which causes a disease of three D or four D [ death ] . - RDA: varies according to age ,sex ,muscular activity ,pregnancy ,lactation and diet mainly the amount of tryptophan in the diet [each 60mg. of tryptophan gives 1 Mg. of nicotinamide and this provides about 10% of RDA]

Vitamin B5 Pantothenic acid is a component of coenzyme A which function in the transfer of acyl group.

-Occurrence : Its found mainly in : meat ,milk, eggs peanut , sweet potatoes and tomatoes . -Deficiency :there are no evidences[facts] for its deficiency in man ,however its deficiency in animals is characterized by : Dermatitis and inflammation of nasal mucosa and Atrophy of adrenal cortex . -RDA : no RDA has established.

Biotin (vitamin B7) Biotin is a coenzyme in carboxylation reactions, in which it serves as a carrier of activated carbon dioxide.

-Occurrence :Vit. B7 is found mainly in meat and milk . it has an important role in : 1 -Fixation of C02 [carboxylation ) . 2-It's a component of the enzyme [ carbamoyl-p- synthetase ] an important enzyme of urea cycle . Deficiency : characterized by : 1 -Dermatitis and depression . 2-Hypocholesterolemia and hallucination . 3-Hair loss . 4-Muscle pain .

-RDA : Varies according to age, sex and individual conditions -RDA : Varies according to age, sex and individual conditions . Normally its about 30-1 00mg./day . Note : consumption of raw eggs can cause Biotin deficiency , because egg white contains a heat labile protein [Avidin] which combines very tightly with Biotin preventing its absorption and inducing its deficiency .