Vitamins Flashcards
Vitamins
Organic compounds Must be obtained from diet Accessory growth factors - fat soluble - water soluble
Provitamins
Consumed in an inactive form and become active vitamins in the body.
Solubility and storage
Water soluble (B group vitamins and C) are absorbed directly into the blood and travel freely, excreted in urine
Fat soluble (ADEK) are absorbed first into the lymph, then the blood. Many require protein carriers, stored in cells associated with fat and are less readily excreted.
Fat soluble vitamins
Can reach toxic levels when supplemented
Closely associated with the absorption and transport of lipids
Optimal absorption requires presence of bile salts
Transported by chlyomicrons
Stored in body lipids
ADEK
Water soluble vitamins
Vit C, B groups
Folate and vit B have synergistic relationship
Can be destroyed by exposure to light, oxidation, cooking and storage. Can be minimised by refrigeration, using air tight wrappers, clean fruits before cut, steam not boil etc.
B vitamins
Do not provide body with energy/ fuel Thiamin Riboflavin Niacin Pantothenic acid Biotin Form part of the coenzyme system that enable release of energy from energy yielding macronutrients
Thiamin B1
Coenzyme thiamin pyrophosphate:
- decarboxylation reactions- during glucose metabolism, TPP decarboxylates pyruvate to form Acetyl coA
- pentose phosphate pathway- metabolises glucose to make products such as monosaccharide deoxyribose for DNA synthesis
- nerve function - ? May help synthesis neurotransmitters or produce energy to fuel nerve tissue
Pork, legumes, nuts, seeds, whole grain cereal products
Thiamin B1 deficiency
At risk:
Alcoholics, alcohol requires thiamin for metabolism, Poor, Elderly, GI disease , HIV
Beriberi- chronic thiamin deficiency first described in countries that subsisted on polished rice
- dry beriberi (without oedema): nerve degeneration, tingling sensation due to loss of nerve transmission, muscle wasting, poor arm and leg coordination, deep pain in calf muscles
- wet beriberi (with oedema swelling): enlarged heart, heart failure, severe oedema
Wernicke- Korsakoff syndrome
Riboflavin B2 functions
Coenzymes involved in numerous metabolic pathways: flavin mononucleotide, flavin adenine dinucleotide
- citric acid cycle critical for energy metabolism
- deamination reaction
- involved in glutathione peroxidase enzymes
Riboflavin involved in conversion of other nutrients- B6 to pyridoxal phosphate, tryptophan to niacin, methylenetetrahydrofolate to methylTHF
Found in milk and milk products, fortified breads and cereals, destroyed by UV light
Riboflavin (B2) deficiency
Ariboflavinosis
- glossitis
- angular stomatitis
- cheilosis
- seborrhaeic dermatitis
- anaemia
No reports of riboflavin toxicity
Niacin (B3)
Two coenzymes formed are:
Nicotinamide adenine dinucleotide
Nicotinamide adenine dinucleotide
Many metabolic pathways that promote synthesis of new compounds rely on NADP
Body can make niacin from tryptophan with help of riboflavin, vitamin B6 and iron
Found in beef, pork, whole grain cereals, eggs, milk
Heat stable
Niacin (B3) deficiency
Pellagra -dermatitis - diarrhoea - dementia Persists in areas of India, China and Africa
Can be toxic if overconsumed- flushing, itching, burning, headaches, liver abnormalities
Pantothenic Acid (vitamin B5)
Part of coenzyme A
Synthesis of fatty acids
Citric acid cycle
Synthesis of amino acids, steroid, neurotransmitter
Found in chicken, beef, potatoes, tomato products, egg yolks
Deficiency very rare, no toxicity
Biotin (vitamin B7)
Carboxylate enzymes Gluconeogenesis Citric acid cycle Fatty acid synthesis Breakdown of amino acids DNA synthesis Initially called vitamin H Found in cauliflower, liver, peanuts
Deficiency- prolonged intake of raw egg whites, use of anticonvulsant drugs, genetic disorders- results in hair loss, rash, neurological disorders
No known toxicity
Vitamin B6
Three forms: pyridoxal, pyridoxine, pyridoxamine
Can all be converted to pyridoxal phosphate (PLP), a coenzyme involved in:
- protein metabolism- synthesis of nonessential amino acids
-CHO metabolism- gluconeogenesis and glycolysis
- blood cell synthesis
- synthesis of neurotransmitter
- Niacin metabolism
Found in fortified cereals, meat, fish, poultry, potatoes
