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OUTLINE

Topic Subtopics

I Introduction

Characteristics

Chemistry

Metabolism

Functions

Sources

IIVitamin A

Deficiency

Causes

Manifestation

Management

Daily Requirements

III Vitamin A Toxicity

Causes

Manifestation

Management

IV Case Report

Case Presentation

Analysis of ManifestationManagement

Vitamins

Nutrition

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OBJECTIVES

1. To discuss the characteristics and

chemistry of Vitamin A2. To discuss Vitamin A metabolism(absorption, storage, transport, excretion)

3. To explain its different functions in the

body

4. To site food sources of Vitamin A

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VITAMIN A

aka ANTI-INFECTIVE VITAMIN

Hydrophobic

Fat-soluble vitamin

Requires SPECIFIC BINDING PROTEINS for transport

Stored in the LIVERand adipose tissues

LESSprone to DEFICIENCY

MOREprone to TOXICITY

CHARACTERISTICS

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VITAMIN A

CHEMISTRY

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VITAMIN A

FORMS

RETINOIDS CAROTENESActiveForm Inactive, Precursor or Provitamin

A

Found in ANIMAL

SOURCES

Found in PLANTSOURCES

Forms of Retinoids:

1. Retinolalcohol form

2. Retinal

aldehyde form3. Retinoic Acidacid

form

4. 3-Dehydroretinol

Important Types in food:

1. Alpha-carotene

2. Beta-carotene

most commonform

3. Gamma-carotene

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FORMS

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Absorption, Storage and

Transport of Vitamin A

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Excretion of Vitamin A

60%is excreted in the URINE

40%in FECES

Thus, the KIDNEYSare the main paths of RBP and

retinol excretion from the body (Stipanuk, 2006; Gropper,Smith, & Groff, 2008; Helwig, 2013)

METABOLISM

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Functions of Vitamin A

1. Vision

FUNCTIONS

2. Gene transcription

3. Skin and cellular health,

Immune function4. Embryonic development

and reproduction

5.Hematopoiesis

6. Bone metabolism

7. Antioxidant activity

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VISION

FUNCTIONS

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GENE TRANSCRIPTION

ALL-TRANS RETINOIC ACIDor 9 CIS RETINOIC ACID

Binds to specific cellularretinoic acid binding

protein

(receptor)

RETINOIC ACID-RECEPTOR COMPLEX

binds to DNA

Regulates the expression ofgenes required for growth and

differentiation

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SKIN & CELLULAR HEALTH

RETINOLinvolved in

the maintenance ofepithelial integrityand glycoprotein

synthesis

RETINOLprevents theexcess keratin

synthesis

RETINOL

PHOPSPHATEformed from retinol

is required forglycoprotein

synthesis

GLYCOPROTEINS areimportant component ofthe MUCUS secreted by

epithelial cells

RETINOL PHOSPHATE forms GLYCOSYLRETINYL PO4 that acts as a donor of

CHO (mannose, galactose, etc.) forGLYCOPROTEIN &

MUCOPOLYSACCHARIDE synthesis

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EMBRYONIC DEVELOPMENT &

REPRODUCTION

RETINOLbinds to specific

intracellular receptor(Cellular RetinolBinding Protein)

RETINOL-RECEPTORCOMPLEX

binds to DNA

Regulates the expression ofgenes required forreproductive function.

[Mechanism of action is similarto steroid hormone action]

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HEMATOPOIESIS

- Process of formation of blood cells inthe living body

VITAMIN A ADEQUACY- Improves hemoglobin concentration

VITAMIN A DEFICIENCY

- Impairs Iron mobilization from stores

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BONE METABOLISM

1st

VITAMIN A (RETINOIC ACID) converts immaturecells to OSTEOBLASTS

2nd

OSTEOBLASTS are responsible for the increase inthe number of Bone cells and OSTEOCLASTS

3rd

OSTEOCLASTS are necessary for the breakdown ofbone cells as bone is remodeled during growth

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ANTIOXIDANT ACTIVITY

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SOURCES OF VITAMIN A

I t was observed that thecontent of vi tamin A in a foodsources depends on i ts color .Therefore, the DARKER green- andDEEPER yel low -co lored ones haveMORE VITAMIN A. However, thevi tamin A ob tained from plants areno t eff ic ient ly ut i l ized as the onesobtained from animals (50% ofcarotenoids whi le 80% forpreformed vi tamin A ). An ind iv idualcan achieve recommended amountof vi tam in A by con sum ing a var ietyof foods from bo th animal and plant

sources (Serraon-Claudio et. al,2004).

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SUMMARY

Fat soluble vitamin Polyisoprene

compound Stored in the LIVER

and adipose tissues Present in food in 2

forms:1. Retinoids (ACTIVE)

ANIMAL source2. Carotenes

(INACTIVE)

PLANTsource

VITAMIN A

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FORM FUNCTION

RETINOL Reproductive function: Transcriptionalregulation of gene expression

RETINOLPHOSPHATE Maintenance of epithelial integrity andGlycoprotein synthesis

RETINOIC ACID Growth & Differentiation:

Transcriptional regulation of gene

expression

11- CIS RETINAL Vision in dim light (Rhodopsin)

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