NUTR1023 Chapter Notes - Chapter 4: Tetrahydrofolic Acid, Triiodothyronine, Homocysteine
Requirements of vitamins !
Vitamin A
Function !
ā¢needed for cell maturation and growth, night and colour vision, reproduction and immunity !
ā¢Retinal = essential in vision !
ā¢Retinoic acid = growth and cellular diļ¬erentiation !
Deficiency !
ā¢night blindness!
ā¢problems with mucous production in eyes which can cause eye infections like xerophthalmia. !
ā¢impact on the skin through dryness!
ā¢poor growth and blockage of hair follicles !
Toxicity!
ā¢ Eating too much yellow can cause hypercarotenaemia (yellow skin)!
Thymine (Vitamin B1)
Function !
ā¢coenzyme in carbohydrate metabolism !
ā¢catabolism of branched chain amino acids !
ā¢key functions in the nervous system !
Deficiency !
Thiamin deļ¬ciency can be seen within 25ā30 days of inadequate intake and is mainly seen in
people suļ¬ering from alcoholism or those at extremes of poverty. !
ā¢reduced carbohydrate metabolism and reduced protein catabolism, and it can have an impact on
the nervous system!
ā¢condition known as beri beri (impairment of nerves and heart)!
ā¢nervous disorders such as poor coordination and tingling. !
ā¢Diļ¬culties in memory retention !
ā¢oedema and weakening of the heart muscle!
ā¢Wernicke-Korsakoļ¬ syndrome may result in people suļ¬ering from alcoholism and who also
consume little food because thiamin is utilised in alcohol metabolism. !
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Toxicity !
ā¢nothing known because of water solubility !
Folate
Function !
ā¢carbon transfer during purine and pyrimidine synthesis!
ā¢ coenzyme involved in DNA synthesis !
ā¢coenzyme in the re-methylation of homocysteine to methionine. !
Deficiency !
ā¢synthesis is highly dependent on vitamin B12 where deļ¬ciencies of the vitamin result in folate
remaining in a 5-methyl tetrahydrofolate form!
ā¢Interaction with vitamin C reduces the loss of folate during cooking. !
ā¢Symptoms of deļ¬ciency include megablastic anaemia, inadequate growth, neural tube defects,
inļ¬ammation of the tongue and diarrhoea !
ā¢At-risk groups include pregnant women and their unborn foetuses as well as persons on
particular medications!
Riboļ¬avin (vitamin B2)
Function !
ā¢%also coenzyme!
ā¢in metabolism of proteins and fats, has a primary role in energy production and adequate
functioning of the immune and nervous systems. !
ā¢key involvement in the conversion of pyridoxine (vitamin B6) to its bioactive form!
ā¢conversion of tryptophan to niacin, and methylenetetrahydrofolate to methyltetrahydrofolate. !
Deficiency !
ā¢ariboļ¬avinosis can result in symptoms of inļ¬ammation of the tongue or the mouth and disorders
of the eye, but it is often seen in conjunction with other deļ¬ciencies. !
ā¢Inadequate intake is more likely in those who do not consume dairy foods. !
Toxicity !
ā¢not reported because of water solubility !
ā¢Increased consumption has been linked with excess urination and diarrhoea, !
Niacin (Vitamin B3)
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Document Summary
Function: needed for cell maturation and growth, night and colour vision, reproduction and immunity, retinal = essential in vision, retinoic acid = growth and cellular di erentiation. Deficiency: night blindness, problems with mucous production in eyes which can cause eye infections like xerophthalmia, impact on the skin through dryness, poor growth and blockage of hair follicles. Toxicity: eating too much yellow can cause hypercarotenaemia (yellow skin) Function: coenzyme in carbohydrate metabolism, catabolism of branched chain amino acids, key functions in the nervous system. Toxicity: nothing known because of water solubility. Function: carbon transfer during purine and pyrimidine synthesis, coenzyme involved in dna synthesis, coenzyme in the re-methylation of homocysteine to methionine. Toxicity: not reported because of water solubility, increased consumption has been linked with excess urination and diarrhoea, Function: component of coenzymes, nicotinamide-adenine and nicotinamide- adenine-dinucleotide phosphate involved in fat synthesis and breakdown as well as energy metabolism. Toxicity: only reported in some countries, symptoms seen as facial ushing.