Community Medicine Lecture -5-
Learning objectivesAt 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 intestineCauses of vitamin deficiency/ cont
C- Miscellaneous including : 1- Renal diseases
ClassificationAccording 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 teratogenicVitamin 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 .
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.
Vitamin D deficiency
In children leads to Rickets. In adults leads to Osteomalacia.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 propertiesVitamin 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 intestineVitamins 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 مضافVitamin 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 result in macrocytic anemia.Sources are liver, green vegetables and formed by intestinal flora.Vitamin B12Its 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 waterPotatoes 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. .