Community Medicine Lecture -5-

Learning objectives At the end of this lecture student would be able to : 1-Determine vitamins general characteristics . 2-Classify vitamins . 3-Determine essential facts about vitamins A,E,K & B complex . 4-Outline clinical presentation of vitamin A deficiency & toxicity . 5-Identify directions of action of vitamin D , clinical features of vitamin D deficiency . 6-Discuss clinical presentation of vitamins B1,B2,nicotinic acid , folic acid , B12 , & vitamin C deficiency .

Vitamins Vitamins are group of organic compounds that are needed in small amounts for maintaining normal metabolism of nutrients and thus promoting the physiological well being of human body.  It cannot be synthesized by human body.  Vitamins vary in their composition and functions.  Its presence in various kinds of food is in a variable amounts.  No optimal food is present i.e. there is no food that contain all essential vitamins to satisfy the daily requirement .

 Vitamins are usually required in a relatively small quantities.  Vitamins Primarily have a catalytic function i.e. it enter in the enzymatic system components which play an important role in facilitating essential metabolic reactions.

Causes of vitamin deficiency A- Decreased intake including : 1- alcohol intake 2- small bowel diseases B-Decreased absorption including : 1- disease due to liver or biliary tract 2- bacterial overgrowth in the intestine

Causes of vitamin deficiency/ cont C- Miscellaneous including : 1- Renal diseases

Classification According to its solubility , vitamins are classified in to :- A-) Fat soluble vitamins It include vitamins A,D,E and K.

Vitamin A (Retinol)  Although vitamin A can be destroyed easily by oxidation ,it is relatively heat stable material.  To a great extent , it is found naturally in its precursors form i.e. carotenoid pro-vitamins alpha, beta and gamma carotene .   Sources are liver , dairy products ,eggs ,green vegetables and carrot . Fish liver is the most concentrated natural source.

Importance of vitamin A 1.It is necessary for the growth of children. 2.It play an important role in the eyes perception to light specially at night (rods and cones photo receptors). 3.It has a protective function for surface tissues e.g. respiratory tract and eye (cornea).

Other effects of vitamin A 1- possible beneficial effects A- protection against cancer B- reduction in cardiovascular events 2- possible adverse effects: 1- retinol is a teratogenic

Vitamin A deficiency Clinically patient will develop:- 1.Night blindness i.e. poor adaptation for dark. 2.Xerosis i.e. changes in the outer layer of sclera resulting in xeropthalmia . 3.Keratomalacia i.e. corneal affection. 4.Cutaneous lesions around the hair follicles. 5.Epithelial changes .

 The daily recommended allowances is 5000 I.U. Vitamin A toxicity Patient clinically will have:- 1.Anorexia . 2.Dry itchy skin . 3.Coarse hair. 4.Swelling over the long bones.  The daily recommended allowances is 5000 I.U.  Additional daily requirement is 1000 I.U. for pregnant woman and 3000 I.U. for lactating woman.

Vitamin D Vitamin D play a major role in increasing the utilization and retention of calcium and phosphorus in the body. Directions of action:- 1.It increase the absorption of dietary calcium and phosphorus from intestinal lumen. 2.It reduce phosphorus excretion in urine through enhancing renal reabsorption of it . 3.It maintain proper calcium and phosphorus levels in blood .This will ensure normal mineralization condition for mature bones.

 In children leads to Rickets.  In adults leads to Osteomalacia. Vitamin D deficiency

Thyroid hormones Both parathyroid and calcitonin hormones with vitamin D are concerned with maintenance of calcium and phosphorus -plasma levels . Sources are liver oil, fish ,egg ,milk and milk products. During summer ,dairy products contain more vitamin D than during winter. Sunlight act on skin and subcutaneous fat and help in the oxidation and formation of vitamin D.

Vitamin E It has some influence on fertility. Sources are green vegetables, milk and milk products. The main function of vitamin E are : 1- antioxidant properties Vitamin E deficiency causing 1- hemolytic anemia

Vitamin K 1-It is found in green plants. 2-It Play a role in prothrombin formation Thus it is essential for normal clotting of blood. 3-Bacterial flora of intestine synthesize vitamin K.

Vitamin K deficiency Vitamin K deficiency lead to defect in clotting factor synthesis and increase in prothrombin time resulting in hemorrhage The deficiency occur in the following conditions : 1- The newborn baby due to poor placental transfer of vitamin K and its little amount present in breast milk 2- Cholestatic jaundice when there is an interruption of the bile flow into the intestine

Vitamins B complex (vitamins B group) Vitamin B1 (thiamine):- Unstable at high temperature . Destroyed by alkaline materials. The main functions of vitamin B1are : 2- Thiamin pyrophosphate is involved in the oxidative decarboxylation of acetyl CoA in mitochondria مقطع مضاف

Vitamin B1 deficiency usually presented as : 1.Affection of children growth. 2.Neuritis. 3.Irritability and depression (psychological symptoms) 4.Beriberi disease -------- a- wet type (in cases of extreme deficiency) b- dry type Sources are seeds, green plants, potato and milk.

B1 deficiency Thiamin deficiency is seen : 1- As beriberi, where the only food consumed is polished rice .

Vitamin B2 (riboflavin) It is easily destroyed by heat, ultraviolet and alkaline materials.  Sources are liver, meat, eggs, and milk.  Features of vitamin B2 deficiency are:- 1.Affection of children growth. 2.Cracks at corners of mouth and nose (Angular stomatitis ) 3.Glossitis ( a red , inflamed tongue )

Nicotinic Acid Niacin is necessary for fatty – acid synthesis Niacin is lost by removing bran from cereals . Niacin is found in plants , meat ( mainly offal ) and fish . Features of nicotinic acid deficiency are: 1. Affection of children growth . 2.Skin affection result in red rough skin. 3.Digestive disturbances and diarrhea.

Folic Acid Its deficiency lead to pernicious anemia. Its deficiency result in macrocytic anemia. Sources are liver, green vegetables and formed by intestinal flora. Vitamin B12 Its deficiency lead to pernicious anemia. Its minimal daily requirements is 0.1  gm. Its liver store depleted in 3-6years. Sources are liver, meat, milk, and fish.

Vitamin C It can be easily destroyed by heat.  Its main sources are fruits, fresh vegetables ,fresh liver ,meat and milk. Ascorbic acid is easily leached out of vegetables when they placed in water Potatoes are a good source , but vitamin C is lost during storage . A dose of 1-2g/ daily of ascorbic acid will prevent common cold

 Features of its deficiency include:- 1. Affection of children growth. 2.Bleeding around hair follicles. .

Vitamin B6 1- It is exists as pyridoxine which is found mainly in plant and animal foodstuffs . 2- Pyidoxal phosphate is a cofactor in the metabolism of many amino acids 3-Some drugs like (isoniazid and penicillamine) interact with Pyidoxal phosphate leading to B6 deficiency .

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