Vitamin A deficiency

SupervisionProf. Dr . Mervat Salah

Intended Learning Outcomes

- By the end of this lecture, students will

have a general overview on vitamin A in it’s

deficiency health outcomes.

BACKGROUND

Vitamins are organic substances that are essential for several enzymatic functions in human metabolismThiamine was discovered in 1912 & was thought to be a vital amine compound & thus the term vitamin was invented

VITAMINS

Vitamins are classified according to solubility into fat soluble & water soluble. 13 vitamins are known, 4 fat soluble (KEDA) & 9 water soluble (C, Folate & the B group).

VITAMIN A Vitamin A is a generic term for many related compounds. Retinol (alcohol), Retinal (aldehyde) are often called preformed vitamin A. Retinal can be converted by the body to retinoic acid which is known to affect gene transcription. Body can convert b-carotene to retinol, thus called provitamin A.

FUNCTIONS

•Vision: integrity of eye & formation of rodopsin necessary for dark adaptation.•Regulation of gene expression: vital to cell differentiation & physiologic processes

•Growth & development

•Immunity: important for activation of T lymphocyte, maturation of WBC & integrity of physiological barrier.

Nutrient Interactions•Zinc deficiency interfere with vitamin A metabolism in several ways: It decreases the synthesis of retinol binding protein, which transports retinol to tissues.

It decreases the activity of the enzyme retinyl palmitate, which is necessary for release of retinol from the liver.

Zn is needed for the enzyme that convert retinol into retinal.

Nutrient Interactions/2•Iron & vitamin A.

Vitamin A deficiency may exacerbate IDFVitamin A supplementation improves iron

status among children & pregnant women.Combining vitamin A with iron controls

IDA more quickly & effectively than using iron alone.

VITAMIN A UNITS

1 mg of retinol = 6 mg of b-carotene. 3 mg of retinol = 10 international units of vitamin A. 100 mg carrots contain 10 mg of b-carotene.

Life stage mg/dayInfants 400-500Children 300-600Adolescent 900M- 700FAdult 900M- 700FPregnant women 750-800Lactating women 122-1300

Recommended Allowance

Animal Foods Plant FoodsCod liver oil Sweet potatoLiver & kidney CarrotsEgg CantaloupeButter SpinachMilk & cheese ApricotFish & meet Papaya

RICH DIETARY SOURCES

Vitamin A deficiency

•Deficiency of vitamin A leads to:Night blindness & xerophthalmiaGrowth retardationAcquired immune deficiencyKeritinization of epithelia in RT, GIT & UT with increased risk of RTI, malabsorption & UTI.

THERAPEUTIC USES

Vitamin A deficiency Boosting immunity of infantsSkin disorders Acute promyelotic leukemia Cancer prevention (lung & breast)

TOXICITY

•Vitamin A in excess leads to:• Dermatitis with xanthosis cutis• Hepatosplenomegaly• Bone pain & increased risk of fracture

• Pseudotumor Cerebri

Xeropthalmia in rat - dryness of the cornea

Early stages are curable

Cured with 6 days treatment with Vitamin A

Vitamin A deficiency Night Blindness

Follicular hyperkeratosis. Goose flesh. Pustulation occurs and is

confused with acne.

Histological section of skin. Hair follicle with hyperkeratosis. (Excess

keratinized tissue).

Recommended text book

Manual dietetic book