Vitmains Flashcards
Vitamin A
Lipid soluble
Retinoids
Ingested directly from meat or produced from carotenes
Vitamin A - deficiency
Rare in affluent countries
May occur due to fat malabsorption
Symptoms - night blindness, xeropthalmia, blindness
Vitamin A - excess
Acute - abdominal pain, nausea, vomiting, headaches, dizziness, sluggishness, desquamation of the skin
Chronic - joint and bone pain, hair loss, dryness of lips, anorexia, weight loss and hepatomegaly
Carotenemia - reversible yellowing of the skin, does not cause toxicity
Vitamin B12
Water soluble
Two active forms - metylcobalamin, 5-deoxyadensylcoalamin
Released from food by acid and enzymes in stomach
Binds to R proteins to protect from stomach acid
Intrinsic factor (IF) produced by stomach needed for absorption
Vitamin B12 - deficiency
Causes - pernicious anaemia, malabsorption, veganism
Symptoms - macrocytic anaemia, peripheral neuropathy in prolonged deficiency
Vitamin C
Water soluble Found in fresh fruit and vegetables Adults need about 40mg/day Used in collagen synthesis Is an antioxidant Used for iron absorption
Vitamin C - deficiency
Scurvy Easy bruising and bleeding Teeth and gum disease Hair loss Treatment with vitamin C releaves symptoms quickly
Vitamin C - excess
Doeses of >1g/day can cause Gi side effects
no evidence that increased vitamin C reduces incidence or duration of colds
Vitamin D
Lipid soluble
Increases intestinal absorption of calcium
Helps resorption and formation of bone
Reduces renal excretion of calcium
Vitamin D - deficiency
Demineralisation of bone
rickets in children
Osteomalacia in adults
can be caused by lack of sun
Vitamin E
Lipid soluble
Stored adipose cells, liver and plasma
Important antioxidant
Men require 4mg/day and Women 3
Vitamin E deficiency
Caused by fat malabsorption, premature infants, rare cogenital defects in fat metabolism Haemolytic anaemia Myopathy Retinopathy Ataxia Neuropathy
Folate
Water soluble
Found in many foods fortified with folic acid
higher requirements in pregnancy
Coenzyme in methylation
Used in DNA synthesis
Used in synthesis of methionine from homocytesine
Folate - deficiency
Causes - malabsorption, drugs that interfere with folic acid metabolism, diseases that increase cell turnover
High homocysteine levels
Macrocytic anaemia
Foetal development abnormalities
Vitamin K
Lipid soluble
Rapidly taken up by liver (but transferred to VLDL and LDL to carry in plasma)
K1 - synthesized by plants and present in food
K2 - synthesized in humans by intestinal bacteria
K3&4 are synthetic
Responsible for activation of some blood clotting factors
Necessary for liver synthesis of clotting factors 10, 9, 7, 2
Can be assesed by measuring prethrombin time
