NUTR1023 Chapter Notes - Chapter 4: Tetrahydrofolic Acid, Triiodothyronine, Homocysteine
Requirements of vitamins !
Vitamin A
Function !
•needed for cell maturation and growth, night and colour vision, reproduction and immunity !
•Retinal = essential in vision !
•Retinoic acid = growth and cellular differentiation !
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)!
Thymine (Vitamin B1)
Function !
•coenzyme in carbohydrate metabolism !
•catabolism of branched chain amino acids !
•key functions in the nervous system !
Deficiency !
Thiamin deficiency can be seen within 25–30 days of inadequate intake and is mainly seen in
people suffering from alcoholism or those at extremes of poverty. !
•reduced carbohydrate metabolism and reduced protein catabolism, and it can have an impact on
the nervous system!
•condition known as beri beri (impairment of nerves and heart)!
•nervous disorders such as poor coordination and tingling. !
•Difficulties in memory retention !
•oedema and weakening of the heart muscle!
•Wernicke-Korsakoff syndrome may result in people suffering from alcoholism and who also
consume little food because thiamin is utilised in alcohol metabolism. !
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Toxicity !
•nothing known because of water solubility !
Folate
Function !
•carbon transfer during purine and pyrimidine synthesis!
• coenzyme involved in DNA synthesis !
•coenzyme in the re-methylation of homocysteine to methionine. !
Deficiency !
•synthesis is highly dependent on vitamin B12 where deficiencies of the vitamin result in folate
remaining in a 5-methyl tetrahydrofolate form!
•Interaction with vitamin C reduces the loss of folate during cooking. !
•Symptoms of deficiency include megablastic anaemia, inadequate growth, neural tube defects,
inflammation of the tongue and diarrhoea !
•At-risk groups include pregnant women and their unborn foetuses as well as persons on
particular medications!
Riboflavin (vitamin B2)
Function !
•%also coenzyme!
•in metabolism of proteins and fats, has a primary role in energy production and adequate
functioning of the immune and nervous systems. !
•key involvement in the conversion of pyridoxine (vitamin B6) to its bioactive form!
•conversion of tryptophan to niacin, and methylenetetrahydrofolate to methyltetrahydrofolate. !
Deficiency !
•ariboflavinosis can result in symptoms of inflammation of the tongue or the mouth and disorders
of the eye, but it is often seen in conjunction with other deficiencies. !
•Inadequate intake is more likely in those who do not consume dairy foods. !
Toxicity !
•not reported because of water solubility !
•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.
