VITAMINS

Dr. Vijay Marakala, MBBS, MD.

Assistant professor BIOCHEMISTRY SIMS & RC

Vitamins are micronutrients

VITAMINS

VITAL+AMINE

Nutrients

VITAMINE

µg-mg/day

VITAMINS

Vitamins are organic nutrients that are required in small quantities for a variety of biochemical functions and which generally

cannot be synthesized in the body and must be supplied by the diet

Definition

VITAMINS

Water soluble

Fat soluble

• B complex• C or Ascorbic acid

• A or Retinol• D or Cholecalciferol• E or Tocopherol• K

Classification

• B1 - Thiamine• B2 - Riboflavin• B3 - Niacin• B5 - Pantothenic acid• B6 - Pyridoxine• Biotin• Folic acid• B12- Cobalamine

Vitamin B complex

Vitamine C or Ascorbic acid

• Water soluble vitaminsVITAMINS

Energy-releasing

Hematopoietic

Other

B1 B2

B3

BiotinPantothenic acid

Folic acidVitamin B12

Pyridoxine

• Vitamins B-complexVITAMINS

Water soluble vitamins Fat soluble vitamins

Solubility Water soluble Fat soluble

Absorption Simple Along with lipids

Storage *No storage Stored in liver

Excretion Excreted Not excreted

Excess intake Nontoxic Toxic

Deficiency Manifests rapidly Manifests slowly

Treatment Regular dietary supply Single large dose

Difference b/w water soluble & fat soluble vitaminsVITAMINS

FAT SOLUBLE VITAMINS

Vitamin A Vitamin D

Vitamin E Vitamin K

VITAMIN

VITAMIN A

Chemistry

Sources

Daily Requirements

Absorption, Transport and

storage

Functions

Deficincy Vitamin A excess

VITAMIN A CHEMISTRY• Vitamin A occurs in two forms in food

Retinoids Retinol

Retinal

Retinoic acid

Carotenes α- carotene

β- carotene

γ- carotene

RETINOIDS

RETINOLRETINAL

RETINOIC ACID

β-ionone ring

β- CAROTENE

VITAMIN A

SOURCES OF VITAMIN A

SOURCES OF VITAMIN A

Polar Bear

One ounce of polar bear liver contains enough vitamin A (retinol) to kill a person!

RECOMMENDED DAILY ALLOWANCE [RDA]

• The daily requirement of vitamin A is expressed as retinol equivalents [RE]

1000 REMEN

800 REWOMEN

1RE = 1µg of retinol = 3.3 IU of retinol

ABSORPTION TRANSPORT ANDSTORAGE

VITAMIN A

RETINA

TARGET TISSUES

ABSORPTION TRANSPORT AND

STORAGE

ABSORPTION TRANSPORT

ANDSTORAGE

FUNCTIONS OF VITAMIN A

Vision : 11-cis retinal [Wald’s visual cycle]Reproduction: Retinol

Growth and differentiation : Retinoic acidEpithelial Integrity : Retinol

ImmunityAntioxidants :β -carotenes

Glycoprotein synthesis

VITAMIN A AND VISION

RODS

RHODOPSIN

11-Cis retinal Opsin

Photoreceptor cells in the retina

Photosensitive pigment

WALD’S VISUAL CYCLE

Rhodopsin cycle comprises two distinct events

Bleaching of rhodopsin & generation of nerve impulse

Regeneration of rhodopsin

WALD’S VISUAL CYCLE

VITAMIN A AND COLOUR VISION

CONES

Porphyropsin

Iodopsin

Cynopsin

Photoreceptor cells in the retinaRequired for vision in daylight and colour identification

VITAMIN A DEFICIENCY

Causes Inadequate intake

Impaired absorption

Impaired storage & transport

Increased excretion [RBP]

Alcoholism

VITAMIN A DEFICIENCY

Features Nightblindness

Xerophthalmia

Bitot spots

Keratomalacia

Infections

Hyperkeratinization of skin

Growth retardation

Bitot’s spot Bitot’s spot

Keratomalacia Xerophthalmia

DIAGNOSIS OF VITAMIN DEFICIENCY

Impaired dark adaptation time

Decreased vitamin A in plasma

Decreased RBP in plasma

Normal plasma vitamin 20 to 80 µg/100ml

VITAMIN A TOXICITY

Over ingestionCauses

Bone and joint pain

Anorexia

Hair loss

Headache

Hepatomegaly

Weight loss