Food and Nutrition continuation

Vitamin B₁ (Thiamin pyrophosphate)

1. Antiberiberi factor: 1926

2. Absorption site: Jejunum/ileum

3. Biological half-life: 10-20 days.

4. Limited tissue storage so continuous supplementation is required.

5. Acts as oxidative carboxylase

6. Acts as co-enzyme with transketolase enzyme in HP shunt.

7. Cofactor for enzymes in arachidonic acid and CHO metabolism.

Dietary source: Yeast, legumes, rice, cereals, etc.

RDA: 1.2- 1.5 mg/day

Deficiency: 1.Beriberi 2.Wernicke- Korsakoff syndrome

Beriberi: Dry & Wet.

Dry beriberi: Peripheral neuropathy of extremities.

Wet beriberi: due to heart failure—cardiomegaly, cardiomyopathy, tachycardia, pitting peripheral edema.

Wernicke encephalopathy: Chronic alcoholic, horizontal nystagmus, ophthalmoplegia, gait ataxia, confusion.

Korsakoff psychosis: recent memory loss.

Vitamin B12

1. Stored in the body as a flavoprotein

2. Poorly soluble in water.

Function: FMN & FAD act as coenzyme.

Source: Milk, green vegetables, meat, yeast, fish, egg, etc.

RDA: 0.5 mg/day

Deficiency: Glossitis.

Niacin

1. Nicotinic acid / Nicotinamide

2. Niacin is synthesized from tryptophan.

Function: NAD/NADP synthesis. Essential for redox reaction & H₂ transport.

Deficiency: 3D= diarrhea, dementia, dermatitis.

Vitamin B6

1. Pyridoxine/pyridoxal phosphate

2. Function: Transamination

3. Deficiency: Peripheral neuropathy.

Vitamin-A

Deficiency of vit-A

1. Repeated respiratory infection

2. Night blindness

3. Xeropthalmia

 a) Conjunctival xerosis

 b) Conjunctival xerosis with bitot spot

 c) Corneal xerosis with corneal ulceration

 d) Corneal perforation leading to softening of eyeball

 e) Keratomalacia leads to blindness.

Forms of vit-A

1. Retinol

2. Retinoic acid

3. Retinaldehyde

4. Beta carotene/provitamin A.

Functions: ---

Retinol

1. Acts as a hormone.

2. It binds with cellular retinol-binding protein & goes to genes where it causes increase transcription & translation & responsible for growth and differentiation of tissue.

3. Retinol is responsible for normal growth and development of cells.

4. A high dose of vitamin A is carcinogenesis.

Retinoic acid

1. Responsible for synthesis & post-translational modification of glycoprotein, this is responsible for the secretion of the sweat gland and lacrimal gland.

Retinaldehyde

1. Acts as a visual pigment and binds with opsins with rods and cones.

2. Phototransduction

Daily requirement: 800-1000 µgm/day

Food source: Animal: Milk, milk product, small fishes, cod liver oil, liver

Vegetable sources: Palm oil, all colored fruits, tomato, banana, spinach, etc.

Vitamin- D

Pathophysiology: Sunlight in the morning is very rich in UV rays. When sunlight falls on stratum basale, 7-dehydro cholesterol converted to cholecalciferol. Then it binds with albumin and goes to the liver. Cholecalciferol is converted into 25, hydroxy cholecalciferol with the help of vit D₃ 25 hydroxylase, an enzyme of the endoplasmic reticulum. Then it goes to kidney tubule and with the help of 1, α – hydroxylase. It is converted into 1, 25, dihydroxycholecalciferol which is then transported to other target organ-like bones, intestinal mucosa and acts like a steroid hormone.

a) In the proximal convoluted tubule, it increases the reabsorption of calcium.

b) In the bone along with parathyroid hormone, it increases the reabsorption of calcium and increases plasma calcium level.

c) Vitamin D increases the mineralization of bone.

Daily requirement: 10 µgm/day

Source: Like vitamin-A

Deficiency: Ricket (Children) and osteomalacia (adult)

Ricket:

a) Delayed dentations

b) Delayed development of milestone of growth

c) Delayed closure of fontanelles.

Features:

1. Bowleg

2. Lock knee

3. Pelvic deformity -à lordosis

4. Greenstick fracture

5. Pigeon chest deformity.

Vitamin-E (Tocopherol)

Sources: Seeds & seed oil, soybean oil, corn oil

Function: acts as an antioxidant.

Deficiency: 1.Hemolytic anemia in children 2. Muscle dystrophy in children 3. Increase fertility and deficiency leads to IUD.

Vitamin-K

1. RDA: 60-70 µgm/day

2. Absorbed from bacterial flora of the intestine.

3. Function: Acts as post-translational modifier at factor 2, 7,9,10.

4. Sources: Green leafy vegetables, liver, meat & vegetable oil.

Vitamin-C (Ascorbic acid)

1. RDA: 100 mg/day

2. Source: Amlaki, guava, orange, green chilly, grapes, fresh citrus foods.

3. Deficiency: Scurvy

4. Function: a) act as a cofactor in hydroxylation reaction in the synthesis of collagen b) synthesis of catecholamine c) Synthesis of bile acid d) Absorption of iron e) Acts as anti-oxidant f) improves wound healing.

Vitamin B12 (Cyanocobalamin)

1. Active form: Methylcobalamin, transcobalamin, hydroxycobalamin, deoxycobalamin, S-adenosyl cobalamin

2. Source: Liver, egg, milk, yeast, shrimp

3. RDA: 3.5 µgm/day

4. Stored in the liver.

5. Function: a) Metabolism of folic acid.

6. Deficiency: (a) Megaloblastic anemia (b) Subacute combine degeneration of spinal cord (c) Peripheral neuropathy (d) Impaired DNA synthesis.

Folic acid

1. Active form: Tetrahydrofolate

2. Function: a) Necessary for the synthesis of DNA b) Involves in the maturation of RBC.

3. RDA: 150-200 µgm/day

4. Deficiency: Megaloblastic anemia

Trace elements

Iodine

1. RDA: 100 µgm/day

2. Source: Seafood, iodized salt

3. Concentrated in the thyroid gland, adrenal gland & skin.

4. The human body contains 30-40 g, thyroid gland 8 gm.

5. Function: Required for organification of thyroxin for the synthesis of T3 & T4.

6. Deficiency: Iodine deficiency disorder—a) Goiter b) congenital hypothyroidism) low IQ: a different variety of mental retardation d) Hypothyroidism.

Zinc

1. Source: Meat, whole grain, legumes

2. Function: a) Associated with some enzyme system, DNA polymerase & transcription enzyme. b) Associated with a proteolytic enzyme, superoxide dismutase.c) required in the diet for normal growth and development of fetus d) Improves wound healing e) in diarrhea- zinc supplementation is required.

3. RDA: 7-10 mg/day

Iron

1. Total body iron: 4-5 gm

2. Distribution form:

a) Hemoglobin in erythrocyte

b) Myoglobin in muscle

c) Respiratory enzymes (cytochrome, catalyzes)

d) Ferritin and hemosiderin as storage form

3. Dietary source: Muscle meat, organ meat, fish, legumes,

4. Daily requirement

a) Children: 10-15 mg b) Adult male: 5-10mg

c) Adult female: 15-20 mg d) Pregnancy: 30-60mg

e) Lactating mother: 30-60 mg

5. Function: a) Constituent of heme enzyme b) Responsible for gas transport

6. Deficiency: Iron deficiency anemia, weakness, brittle fingernail, angular stomatitis, glossitis, smooth tongue.