micronutrients Flashcards
what are micronutrients?
vitamins and tracelements
what are the roles of micronutrients?
cofactors coenzymes antioxidants genetic control structure
what are cofactors? give an example
non-protein chemical compound or metallic ion required for a protein’s biological activity to happen. E.g. iron/zinc
what are coenzymes? give an example
Small non-protein organic molecule. Cannot by themselves catalyze a reaction but they help enzymes to do so. E.g. thiamine pyrophosphate (TPP
what are antioxidants? give an example
inhibits the oxidation of other molecules. E.g. beta-carotene/vitamin C
give examples of micronutrients involved in genetic control?
vitamins A and D
how are micronutrients involved in structure? give examples
Phospholipids form complexes with both Mg” and Ca”. These complexes are integral parts of the various membranes in the cell
why are micronutrients needed in children?
needed for energy supply and body growth and development
what does the recommended dietary allowance define?
how many micronutrients we need
limits for deficiency and toxicity
how do fat-soluble vitamins enter the portal circulation?
micelle –> chylomicron to get into the intestinal lining –> portal circulation
how do water soluble vitamins enter the portal circulation?
directly through the intestinal lining
give examples of fat soluble vitamins?
A D E K
give examples of water soluble vitamins?
B, folate, biotin, C
can fat soluble vitamins be stored?
yes
can water soluble vitamins be stored?
no
what happens to excess fat soluble vitamins?
become toxic
what happens to excess water soluble vitamins?
excreted in the urine
what are the causes of vitamin deficiency in developed countries?
decreased intake of vitamins
decreased absorption
others - renal disease or drug antagonists
what can cause a decreased intake of vitamins?
alcohol dependency - lack of vitB1 small bowel disease - B9 vegans - vitD and B12 elderly w poor diet - D anorexia - folate
what can cause decreased absorption of vitamins?
ileal disease - only B12
liver and biliary tract disease - fat soluble vitamins
intestinal bacteria overgrowth - B12
oral antibiotics - K
what is the clinical feature and contributing factor to deficiency in vitamin A
Infection, measles, protein-energy malnutrition
Xerophthalmia
what is the clinical feature and contributing factor to deficiency in vitamin D
Aging, lack of sunlight
Rickets, oestomalacia
what is the clinical feature and contributing factor to deficiency in vitamin E
Antibiotic use
peripheral neuropathy
what is the clinical feature and contributing factor to deficiency in vitamin K
antibiotic use
coagulpathy
what is the clinical feature and contributing factor to deficiency in vitamin C
smoking
scurvy
what is the clinical feature and contributing factor to deficiency in vitamin B1
Concommittant Vitamin B6, B12 & folate deficiency
beri beri
what is the clinical feature and contributing factor to deficiency in vitamin B2
malabsorption
Magenta tongue, angular stomatitis
what is the clinical feature and contributing factor to deficiency in vitamin B3
Vitamin B6 deficiency, riboflavin deficiency
pellagra
what is the clinical feature and contributing factor to deficiency in vitamin B6
Isoniazid use
anaemia
what is the clinical feature and contributing factor to deficiency in vitamin B12
Gastric atrophy (pernicious anemia),
terminal ileal disease, strict
vegetarianism
anaemia
what is the clinical feature and contributing factor to deficiency in folate
Sulfasalazine, pyrimethamine, triamterene
anaemia
what is kwashiorkor disease?
a severe form of malnutrition caused by lack of dietary protein
what is marasmus?
a severe form of malnutrition that occurs in children. causes muscle wasting/protein loss
why is nutrition important?
Impaired wound healing and immune response
Reduced muscle strength
Inactivity leads to pressure sores and thromboembolism
Increased risk of postoperative complications
Depression and self-neglect
what does iron deficiency lead to?
anaemia, lethargy and constitutional disturbance
microcytic anaemia, lethargy and fatigue, cognitive impairment in children
what is iron needed for?
oxygen transport in haemoglobin and myoglobin function in skeletal muscle
where is iron absorbed?
upper small bowel
how and where is iron stored?
stored in liver and bone marrow as ferritin
what does iron excess lead to?
haemochromatosis, lethargy and fatigue, abdominal and joint pain, reduced libido, bronzing of skin, diabetes, cirrhosis
what lifestyle factors contribute to vitamin D deficiency?
obesity, smoking, alcohol and exercise
what disease factors contribute to vitamin D deficiency?
reduced skin synthesis, decreased bioavailability, drug-related, increased excretion, acquired (e.g. TB)
what does rickets lead to?
growth retardation and the expansion of the growth plate
what is osteomalacia?
reduced bone strength
what does osteomalacia lead to?
increase in bone fracture, bone pain, bending of bones, muscle weakness and waddling gait
what does thiamine deficiency lead to?
Wernicke’s Encephalopathy and Korsakoffs Psychosis
what is thiamine?
vitamin B1
where is thiamine absorbed?
jejunum
what is thiamine used for?
glycolysis, Krebs cycle, BCAA metabolism, pentose phosphate cycle metabolism
which vitamin is niacin and where is it absorbed?
B3
jejunum
what is niacin a generic name for?
nicotinic acid and nicotinamide
what can cause niacin deficiency?
Vegetarian diet
o Hartnup’s disease - Congenital defects of intestinal and kidney absorption of tryptophan
o Carcinoid syndrome - Increased conversion of tryptophan to Serotonin
o Isoniazid use - TB treatment
what are early symptoms of pellagra?
loss of appetite, generalised weakness, irritability, abdominal pain, vomiting and bright-red glossitis
what are late symptoms of pellagra?
Casal’s necklace, vaginitis, oesophagitis, diarrhoea, depression and seizures
what is Casal’s necklace?
skin rash particularly in areas exposed to sunlight
what are the 4 Ds of pellagra?
dermatitis, diarrhoea, dementia , death
what does folate deficiency cause in foetuses?
neural tube defects
what can cause a B12 deficiency?
Inadequate intake: vegans Disorders of terminal ileum Defective release of cobalamin from food Inadequate production of IF Transcobalamin II deficiency (rare) Congenital enzyme defects (rare)
