Water Soluble Vitamins Overview

Water Soluble Vitamins

Water-soluble vitamins are chemically unrelated organic compounds that cannot be synthesized in adequate quantities by humans. They must be supplied by the diet.
Key objectives for the lecture include understanding the biochemical functions of vitamin C, vitamin B complex functions, symptoms of vitamin C deficiency, and diseases resulting from vitamin B complex deficiencies.
Ascorbic acid (vitamin C) and dehydroascorbic acid have antiscorbutic activity.
Recommended daily allowance (RDA) for vitamin C is 75 mg/day (equivalent to 50 ml of orange juice). During pregnancy, lactation, and in older adults, the requirement may increase to 100 mg/day.
Vitamin C is essential for the hydroxylation of proline and lysine which is crucial for the normal production of supporting tissues like osteoid, collagen, and intercellular cement substance of capillaries.
Vitamin C enhances iron absorption by reducing ferric iron to ferrous iron, which is more readily absorbed.
It plays a role in hemoglobin metabolism, converting met-hemoglobin back to hemoglobin.
As an antioxidant, vitamin C may prevent cancer formation.
Scurvy, is a result of gross vitamin C deficiency. In severe cases, gums become painful, swollen, and spongy. Pulp separates from dentine and teeth may be lost. Healing of wounds may also be delayed.
Vitamin C deficiency can lead to microcytic, hypochromic anemia. Internal hemorrhaging (epistaxis, hematuria, malena) might also occur. Hemorrhages could occur in the conjunctiva and retina.
Bone formation can fail due to the deficiency of vitamin C in the osteoblasts. Hemorrhage may occur in the joint cavities.

Thiamine (Vitamin B1)

Thiamine pyrophosphate is the biologically active form of thiamine.
Thiamine pyrophosphate serves as a coenzyme in the oxidative decarboxylation of α-keto acids.
Beriberi is a severe thiamine-deficiency syndrome that occurs in areas with diets primarily made of polished rice.
Infantile beriberi symptoms include tachycardia (rapid heartbeat), vomiting, convulsions, and potentially death without treatment.
Adult beriberi symptoms include dry skin, irritability, disordered thinking, and progressive paralysis.

Riboflavin (Vitamin B2)

The biologically active forms of riboflavin are flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD).
FMN and FAD are tightly bound to flavoenzymes that catalyze the oxidation or reduction of a substrate.
Riboflavin deficiency may result in dermatitis, cheilosis (fissuring at the corners of the mouth), and glossitis (a smooth and purplish tongue).

Niacin (Vitamin B3)

The biologically active coenzymes are nicotinamide adenine dinucleotide (NAD+) and nicotinamide adenine dinucleotide phosphate (NADP+).
NAD+ and NADP+ are coenzymes in oxidation-reduction reactions.
Pellagra, a disease affecting skin, gastrointestinal tract, and the central nervous system (CNS), results from niacin deficiency.
Symptoms progress through the three Ds: dermatitis, diarrhea, dementia, and if untreated, death.

Pantothenic Acid (Vitamin B5)

Pantothenic acid is a component of coenzyme A (CoA).
CoA functions in the transfer of acyl groups.
Pantothenic acid deficiency isn't well studied in humans.

Pyridoxine (Vitamin B6)

Vitamin B6 encompasses pyridoxine, pyridoxal, and pyridoxamine. All are pyridine derivatives.
All three compounds serve as precursors of the biologically active coenzyme pyridoxal phosphate.
Pyridoxal phosphate functions as a coenzyme for numerous enzymes, particularly those involved in amino acid reactions.
Dietary pyridoxine deficiencies are rare but observed in some newborn infants fed formulas low in B6, women on oral contraceptives and alcoholics.
Pyridoxine (vitamin B6) is the only water-soluble vitamin with significant toxicity.
Neurologic symptoms (sensory neuropathy) can occur with intakes exceeding 200 mg/day — much higher than the recommended daily allowance (RDA).

Biotin (Vitamin B7)

Biotin is a coenzyme in carboxylation reactions, acting as a carrier for activated carbon dioxide.
Biotin deficiency is uncommon because the vitamin is widely distributed in food, with substantial contribution provided by intestinal bacteria.

Folic Acid (Vitamin B9)

Tetrahydrofolate (reduced folate) participates in amino acid, purine, and thymidine monophosphate (TMP) synthesis (a pyrimidine in DNA).
Folic acid deficiency commonly arises from increased demands (e.g., pregnancy, lactation), poor absorption (e.g., small intestine pathology, alcoholism), or treatment with dihydrofolate reductase inhibitors like methotrexate.
Folic acid deficiencies result in macrocytic anemias (specifically megaloblastic). Accumulation of large, immature red blood cell precursors (megaloblasts) occurs in the bone marrow and blood.
Folic acid supplementation during the first trimester of pregnancy can prevent neural tube defects in the fetus, such as spina bifida and anencephaly. Therefore, women of childbearing age are advised to consume 0.4 mg/day of folic acid.

Cobalamin (Vitamin B12)

Vitamin B12 is essential for metabolism, red blood cell production, and central nervous system maintenance.
Unusual fatty acids accumulate and incorporate into cell membranes (including nervous system membranes) when vitamin B12 is deficient, leading to neurological manifestations.
Unlike many other water-soluble vitamins, 4-5 mg of vitamin B12 is stored in the body.
Pernicious anemia is not typically a result of dietary B12 deficiency but rather malabsorption in elderly individuals due to reduced gastric acid secretion. This leads to less effective absorption of vitamin B12 from food.