N/MET BIOCHEM 1: Fat soluble vitamins

What is the definition of vitamins, and their properties?

Vitamins are organic nutrients that are:

• Required in small amounts

• Cannot be synthesized by the body and must be supplied by the diet

• They are essential for a variety of biochemical functions which are required for the normal growth, development and maintenance of life.

• Does not provide energy

What are the two main groups of vitamins?

Vitamins are classified based on solubility.

Vitamins are divided into two main groups:

1) Fat soluble vitamins: Vitamins K, E, D, A.

2) Water soluble vitamins: Vitamins B group and C

Compare water soluble and fat soluble vitamins

What are the sources and the functions of vitamin K? (Anti-hemorrhagic vitamin)

(Vit K is like: hey, dont bleed twin)

Sources:

• K1 in plants as cabbage, cauliflower, and spinach

• K2 in egg yolk & liver. It is synthesized by the bacteria in the gut.

• K3 is synthetic.

Functions:

• Essential for clotting of blood, for synthesis of blood clotting factors II, VII, IX and X (2, 7, 9, 10) in the liver, conversion of prothrombin to thrombin, and the formation of fibrinogen to fibrin, leading to clot formation

• Stimulates bone formation and decreases bone reabsorption.

What may cause vitamin K deficiency, and what are its manifestations?

Deficiency is rare, but may occur in:

• New born because there is no intestinal bacteria.

• Biliary obstruction and liver diseases

• Prolonged use of antibiotics which kills the intestinal bacteria.

• Decreased intake.

Manifestations:

• Hemorrhage and bleeding.

• Prolonged prothrombin time

HYPERVITAMINOSIS K (vitamin toxicity) is rare

What are the sources and the functions of vitamin E? (Tocopherol, anti-sterility vitamin)

(Vit E is like: ill protect your red blood cells twin, and while im at it ill make rats fertilie too yk)

Sources:

• Excellent sources are vegetable oils.

• Moderate sources like liver, milk, egg yolk.

Function:

• It is the most important natural anti-oxidant. ( It protects the RBCs from toxic haemolysis particularly in patients with reduced G6PD)

• Important in reproduction in rats and some animals

What are the manifestations of vitamin E deficiency?

• Haemolytic anemia (due to oxidation of polyunsaturated fatty acids (PUFAs)

• Sterility in mice.

Hypervitaminosis E rare

What are the sources and the functions of vitamin D? (Anti-rachetic vitamin)

(Vit D is like ay ay let my boy calcium in)

Sources:

• Fish liver oils, liver and egg yolk.

• Sunlight (7-dehydrocholesterol passes to skin where by the effect of UV rays then is converted to vitamin D)

Functions:

Maintains adequate serum calcium level by=

• Increasing absorption and uptake of calcium by intestine.

• Decreasing loss of calcium by the kidney.

• Stimulate reabsorption of bone and mobilization of Ca and PO4 from bone when parathyroid hormone (PTH) is released in response to low serum calcium.

Explain the activation of Vitamin D

Vitamin D2 and D3 are not biologically active. They are converted in vivo to the active form by two hydroxylation reactions:

• Hydroxylation of vitamin D3 at the 25-position in the liver results in the formation of 25-OH D3.

• 25-OH D3 is further hydroxylated at the one in the kidney resulting in the formation of 1-25 OH D3 (Calcitriol).

What may cause vitamin D deficiency, and what are its manifestations?

Causes:

• Decreased intake

• Decreased absorption (due to biliary obstruction)

• Decreased exposure to sunlight.

• Decreased activation of vitamin D (liver and kidney diseases).

Manifestations:

In Children: Rickets

• Failure of bones to grow properly

• Delayed sitting, walking & teething.

• Deformed bones (skull, chest and legs)

• Decrease of Ca & P in the blood

In Adult: Osteomalacia.

• Bone deformation

• Bone fracture

• Decrease of Ca & P in the blood

What are the manifestations of vitamin D toxicity?

Vitamin D is the most toxic vitamin. (He gets angry if you over-invite calcium, there are limits to their friendship.)

Manifestations:

• Loss of appetite, nausea and thirst.

• Calcification of soft tissue: hypercalcemia leads to calcium deposit in Lungs, heart, blood vessels.

• Hardening of arteries.

• Stone formation in kidneys.

Does not occur from sunlight or dietary sources but DOES occur with supplementation

What are the sources and functions of vitamin A? (Anti-xerophthalmic vitamin)

(Vitamin A is like: I wont let your eyes dry twin, don’t worry)

Sources:

• Present only in animal sources as liver, kidney, butter, milk and egg yolk.

• Fish liver oil

• Carotenes (provitamin A) are present in yellow and green vegetables and fruits as spinach, carrots

Functions:

• Colored vision and night vision

• Supports overall normal cellular growth

• Reproduction

• Necessary for healthy skin & hair growth

• Maintenance of integrity of epithelial tissues as skin, mucus membranes.

• Antioxidant (carotene)

• Anticancer activity

What are the manifestations of vit A deficiency and toxicity?

Manifestations of deficiency:

• Defective night vision.

• Failure of growth.

• Reproductive disorders.

• Loss of health and integrity of epithelial tissues as the skin and mucus membrane.

• Dryness of the eye (Xerosis).

Manifestations of toxicity:

Due to excessive use of vitamin A supplements.

• Headache

• Drowsiness

• Nausea

• Skin & bone abnormalities

• Congenital malformations.

• Dry itchy skin

• Hair loss