Unit 2, lesson 3, part 2+3, vitamin B and part 4 vitamin c

• Water-soluble vitamins are easily dissolved in water and readily absorbed into tissues.
• They are less likely to accumulate in the body.
• They must be replenished more often than fat-soluble vitamins.

B Group Vitamins

• Initially believed a single vitamin, it is now known to be multiple vitamins.
• They all form coenzymes.
• Vitamins were named based on the order of discovery.
• Some B vitamins were later found to be produced by the body and are no longer classified as vitamins.
• Examples of these non-vitamins are B4, B8, B10, and B11.
• B vitamins are classified together due to their presence in similar foods.
• Differences exist in structure and function.
• Some B vitamins can be synthesized within the body by intestinal flora.
• This is different from being produced by the body.

Vitamin C (Ascorbic Acid)

• Found in citrus fruits, guava, kiwi, broccoli, and Brussels sprouts.
• In 1747 the benefits of citrus juice over scurvy were shown in the first clinical trial.
• Ascorbic acid acts as a cofactor.
• A powerful reducing agent that occurs naturally in living tissue.
• It acts as a cofactor in the hydroxylation of proline to hydroxyproline, creating more OH groups for H-bonding making the triple helix of collagen stronger.
• Ascorbic acid maintains metal ions(cofactors) in the correct ionic state within an enzyme's active site, such as Fe2+ in the active site of prolyl hydroxylase.
• Ascorbic acid acts as a cofactor in steroid synthesis, noradrenaline production, and the conversion of folic acid to THF.
• Ascorbic acid has an independent role as an antioxidant- donating electrons to limit the damage caused by free radicals and oxidative species.
• Ascorbic acid is involved in immune system regulation, especially during infection.

Scurvy and Vitamin C Toxicity

• Scurvy is characterized by swollen gums, bruising, haemorrhage, bone fracture, loose teeth, poor wound healing, and anaemia.
• Supplements may benefit those not following a balanced diet, such as the elderly, infirm, diabetics, pregnant and lactating women, and heavy drinkers
• Vitamin C toxicity may cause stomach complaints.

Vitamin B1 (Thiamine)

• Found in cells so it is present in all whole natural foods, like whole cereal grains, beans, fruits and yeast.
• Produces the coenzyme thiamine pyrophosphate, TPP.
• TPP functions as a coenzyme to carbohydrate metabolism enzymes.
• These enzymes help to release energy from food.
• Also involved in conduction of action potentials in neurons and neuro-muscular transmission.
• Deficiency is prevalent in eastern Asia, where white rice (containing too little thiamine) is a staple.
• Deficiency is also common in chronic alcoholics (severely malnourished).
• Athletes and pregnant/lactating women may require supplements due to increased carbohydrate consumption.
• Beriberi, caused by thiamine deficiency, can affect different organ systems.
• Wet beriberi affects the cardiovascular system, presenting with cardiac failure, dyspnoea, and oedema.
• Dry beriberi affects the peripheral nervous system, presenting with peripheral neuritis, paralysis, and wastage.
• Wernicke-Korsakoff syndrome, a severe form of dry beriberi, is characterized by paralysis.

Vitamin B2 (Riboflavin)

• The sources of Vitamin B2 are dairy products, eggs, green vegetables, and almonds.
• It produces Flavin mononucleotide (FMN) and Flavin adenine dinucleotide (FAD) coenzymes.
• The heterocyclic system acts as a H acceptor or/and donor.
• The coenzymes act as prosthetic groups on a family of mainly oxidoreductase enzymes, known as flavoproteins.
• Involved in the metabolism of fats, carbohydrates, and proteins.
• Also acts as a coenzyme in the processing or conversion of vitamin B6 into its active form.

Vitamin B2 Deficiency

• Rare in developed countries where foods are fortified, the deficiency is common in developing countries due to malnutrition.
• Symptoms include inflammation of the mouth and lips (stomatitis), similar to pellagra without widespread skin lesions.
• Riboflavin deficiency can reduce iron absorption, leading to normocytic anaemia.

Vitamin B3 (Niacin)

• Vitamin B3 is also known as Nicotinamide (Niacinamide) or Niacin (Nicotinic Acid).
• Sources include meat, fish, and nuts.
• Nicotinamide is also used in acne treatments.
• Vitamin B3 produces the coenzymes, Nicotinamide adenine dinucleotide (NAD) and Nicotinamide adenine dinucleotide phosphate (NADP).
• NAD(P)+ os an oxidising agent, while NAD(P)H is a reducing agent.
• NADPH is important in anabolic processes, such as lipid and nucleic acid synthesis.
• NAD+ is vital to catabolic processes like fatty acid and glucose metabolism.
• The body doesn't depend entirely on dietary intake of Niacin, since nicotinic acid can be produced in vivo from dietary tryptophan.

Vitamin B3 Deficiency (Pellagra) and Toxicity

• Deficiency is common in areas where maize is the principal foodstuff because maize has low nicotinic acid and tryptophan.
• Pellagra symptoms include dermatitis, diarrhoea, and dementia.
• Chronic alcoholics are also at risk.
• Skin flushes and liver damage are mainly seen with niacin supplementation.
• Nicotinamide may be given as an alternative supplement.

Vitamin B5 (Pantothenic Acid)

• Sources of Vitamin B5 include dairy products, eggs, avocado and mushrooms.
• The vitamin is present in the outer layers of whole grains.
• Milling can greatly reduce its content in foods.
• The coenzyme produced is Coenzyme A.
• Involved in the synthesis and oxidation of fatty acids.
• It is involved in the oxidation of pyruvate as part of the Krebs cycle.
• Deficiency is extremely rare and its effects have not been thoroughly studied.

Vitamin B6

• Vitamin B6 is also known as pyridoxine, pyridoxal, pyridoxamine.
• Sources include most foods of vegetable (pyridoxine) or animal origin (pyridoxal, pyridoxamine) origin.
• The forms are interconvertible via their phosphates in vivo.
• The coenzyme produced is pyridoxal-5'-phosphate.
• Involved in tryptophan metabolism; deficiency is a risk factor for vitamin B3 deficiency.
• It is also involved in the production of neurotransmitters like dopamine and GABA.
• It functions an extremely broad range of enzymes, approximately 4% of enzymes, >140 reactions.
• Vitamin B6 Deficiency is rare because most diets contain adequate amounts and some is synthesised by intestinal flora.
• Deficiency can result disorders of the CNS, skin and mucous membranes.
• Patients on medicines like isoniazid may benefit from increased Vitamin B6, to counter increased excretion of pyridoxine.

Vitamin B6 Toxicity

• Supplementation with high doses of vitamin B6 can lead to nerve damage.
• This particularly affects spinal ganglia and manifests as pain or numbness in the extremities.
• In extreme cases, it can cause difficulty with motor functions.

Vitamin B7 (Biotin)

• Food sources of Vitamin B7 is egg, avocado, yeast, and fresh vegetables.
• N/A, biotin acts as a coenzyme.
• Vitamin B7 is required by several carboxylase enzymes that are involved in fatty acid synthesis, amino acid breakdown and glucose synthesis (gluconeogenesis).
• A severe deficiency has never been reported in healthy individuals eating a normal mixed diet.
• Deficiency presents with thinning hair, brittle nails, rashes, and neurological symptoms.
• Pregnant/lactating women are at risk of deficiency due to unknown clinical reasons.
• Consumption of lots of raw eggs puts people at risk of deficiency owing to avidin in the whites reducing the absorption of biotin.

Vitamin B9 (Folic Acid)

• Nuts, seeds, chickpeas, and green vegetables are sources for Vitamin B9.
• Folic acid is the vitamin that is most commonly added to 'fortified' foods such as flour.
• The coenzyme produced is tetrahydrofolate (THF).
• THF assists enzymatic reactions that transfer hydroxymethyl (-CH2OH), formyl (-CHO), and methyl (-CH3) groups.
• Participates in the synthesis of amino acids and purine/pyrimidine bases for DNA formation.
• Deficiency can effect patients with malignant disease or patients who are pregnant/breastfeeding due to folic acid demand.
• Some medications, e.g. methotrexate, can interfere with folic acid processing.

Vitamin B9 Deficiency

• Deficiency during pregnancy increases the risks of low birth weight, premature birth, and neural tube defects.
• Supplements are given during pregnancy, leukaemia, and drug-induced folate deficiency.
• Deficiency can cause megaloblastic anaemia (large red blood cells) due to faulty erythrocyte multiplication and maturation.

Vitamin B12 (Cobalamin)

• Animal sources of Vitamin B12 include meat, fish, milk, and eggs.
• Vitamin B12 is rare in plant-based foods, but some is found in fermented foods and seaweed.
• The body converts hydroxocobalamin and cyanocobalamin from the diet into the active forms adenosylcobalamin and methylcobalamin.
• Acts as a cofactor for methionine synthase, which participates in THF production from folic acid.
• It also acts as a cofactor in molecular rearrangement reactions, exemplified by metabolism of branched-chain amino acids, particularly in the central nervous system.

Vitamin B12 Deficiency

• Deficiency causes pernicious anaemia, i.e. megaloblastic anaemia along with gastrointestinal and neurological symptoms.
• Folic acid supplementation can reverse the megaloblastic anaemia but will not reverse the other symptoms.