Overview of Vitamins

Overview of Vitamins

• Essential organic nutrients required in small amounts for various biochemical functions.
• Cannot be synthesized by the body; must be obtained through diet.
• Classified as fat-soluble (A, D, E, K) or water-soluble (B complex, C).

Fat-Soluble Vitamins

• Require bile acids for digestion and are transported in blood as chylomicrons to the liver.
• Efficient absorption depends on normal fat absorption; stored in the liver and adipose tissue.
• Higher risk of toxicity compared to deficiencies.
• Good sources include fatty foods and liver.

Water-Soluble Vitamins

• Generally non-toxic; must be continuously supplied in the diet.
• Stored in small amounts; greater loss occurs via urinary excretion.
• Function primarily as coenzymes in enzymatic reactions.

Vitamin A

• Derived from β-carotene and is chemically known as retinol.
• Sources include animal-derived foods (meat, liver, fish oils) and fortified products (milk, margarine).
• Important for maintaining plasma calcium levels (normal range: 9-11 mg/dl).

Vitamin D Functions and Deficiency

• Deficiency leads to rickets in children and osteomalacia in adults.
• Causes include insufficient dietary intake, limited sunlight exposure, absorption issues, and abnormal conversion to active metabolites.
• Chronic renal failure can lead to renal rickets due to inadequate active vitamin D formation.

Symptoms of Vitamin D Deficiency

• Characterized by bowed legs and beaded ribs in rickets.

Hypervitaminosis D

• Toxic effects include bone resorption and hypercalcemia.
• Symptoms: loss of appetite, nausea, increased thirst, and weight loss.
• Key measurements include serum levels of 25(OH)D3 and 1,25(OH)2D3.

Vitamin E

• Composed of eight tocopherols; α-tocopherol is the most active form.
• Acts as a terminal electron acceptor in cell membranes and protects against lipid peroxidation.
• Major sources are oils (especially wheat germ oil), nuts, meat, milk, and eggs.
• Deficiency symptoms include increased fragility of erythrocytes and minor neurological issues.

Vitamin K

• Exists as phylloquinone (K1, from plants) and menaquinone (K2, produced by intestinal bacteria).
• Plays a crucial role in blood clotting and bone matrix formation, with sources including pork, whole grains, and legumes.

Thiamine (Vitamin B₁)

• Acts as a co-enzyme in carbohydrate metabolism and branched-chain amino acid metabolism.
• Deficiency leads to ‘beri-beri’, affecting organs with high aerobic metabolism, notably the heart and nervous system.
• Symptoms include wet beri-beri (cardiovascular issues) and dry beri-beri (neurological symptoms).

Wernicke-Korsakoff Syndrome

• Associated with chronic alcoholism, resulting from dietary insufficiency or impaired absorption, causing memory loss and ocular symptoms.

Measurement of Thiamine

• Evaluated by transketolase activity in erythrocytes; deficiency indicated by >25% increase after TPP addition.
• Detection methods include HPLC.

Riboflavin (Vitamin B₂)

• Exists in active forms: FMN and FAD, which are crucial for oxidation-reduction reactions.
• Sources include milk, liver, eggs, and leafy vegetables.
• Deficiency may cause dermatitis, cheilosis, and glossitis; not associated with major diseases.

Niacin (Vitamin B₃)

• Composed of two forms: nicotinic acid and nicotinamide.

This quiz provides an overview of vitamins, highlighting their essential roles as organic nutrients and their classifications as fat-soluble and water-soluble. You'll learn about their digestion, absorption, and storage in the body, alongside potential toxicity risks. Test your knowledge on the critical functions these nutrients serve in maintaining health.