Vitamin C: Sources, Functions, and Deficiency
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Questions and Answers

What is the ratio of carotene to retinol in terms of potency?

  • 6:1 (correct)
  • 2:1
  • 1:2
  • 4:1

    • What is the primary function of retinoic acid in the body?

  • Hormone-like activity (correct)
  • Cell growth and differentiation
  • Antioxidant activity
  • Vision

    • During which type of vision is 11-cis retinal most important?

  • Cone vision
  • Photopic vision
  • Scotopic vision (correct)
  • Mesopic vision

    • How is retinol transported from the liver to the tissues?

    <p>Bound to a specific retinol binding protein</p> Signup and view all the answers

    What is a common association with vitamin A deficiency?

    <p>Inadequate protein diets</p> Signup and view all the answers

    What is a late-stage complication of vitamin A deficiency?

    <p>Keratomalacia</p> Signup and view all the answers

    What is a potential side effect of excessive vitamin A supplementation?

    <p>All of the above</p> Signup and view all the answers

    What is the unit of measurement for retinol potency?

    <p>Retinol equivalents (RE)</p> Signup and view all the answers

    What is the primary function of vitamin C in collagen formation?

    <p>Hydroxylation of proline and lysine</p> Signup and view all the answers

    What is the recommended daily intake of vitamin C for smokers?

    <p>80 mg/day</p> Signup and view all the answers

    What is a potential risk of taking megadoses of vitamin C?

    <p>Kidney stones in susceptible individuals</p> Signup and view all the answers

    What is the primary cause of vitamin deficiency?

    <p>Dietary deficiency</p> Signup and view all the answers

    What is the primary source of vitamin A?

    <p>Animal liver and fish liver oils</p> Signup and view all the answers

    What is the effect of vitamin C deficiency on the body?

    <p>Impaired wound healing and haemorrhages</p> Signup and view all the answers

    Who is at risk of vitamin C deficiency?

    <p>All of the above</p> Signup and view all the answers

    What is the effect of megadoses of vitamin C on the body?

    <p>Uncertain benefits and potential risks</p> Signup and view all the answers

    What is the recommended daily intake of vitamin E in pregnancy?

    <p>3.3 mg/day</p> Signup and view all the answers

    What is the primary function of vitamin E in the body?

    <p>To prevent oxidation of unsaturated fatty acids</p> Signup and view all the answers

    What is the outcome of a fatty acid radical reacting with oxygen?

    <p>A peroxyl radical is formed</p> Signup and view all the answers

    What is the characteristic effect of vitamin E deficiency in premature infants?

    <p>Haemolytic anaemia</p> Signup and view all the answers

    What is the role of vitamin E in protecting against cardiovascular disease?

    <p>It protects fatty acids and apoprotein B in LDL from oxidative damage</p> Signup and view all the answers

    What is the primary source of vitamin E in the diet?

    <p>Vegetable oils, especially wheat germ oil</p> Signup and view all the answers

    What is the effect of vitamin E deficiency on human milk?

    <p>It is not a significant source of vitamin E</p> Signup and view all the answers

    What is the relationship between vitamin E intake and polyunsaturated fatty acid intake?

    <p>Vitamin E intake is likely to be higher with high PUFA intake</p> Signup and view all the answers

    What is the primary source of vitamin K in infants?

    <p>Bacterial flora of the gut</p> Signup and view all the answers

    Why do infants have a marginal insufficiency of vitamin K?

    <p>All of the above</p> Signup and view all the answers

    What is the consequence of vitamin K deficiency in terms of blood clotting?

    <p>Increased blood clotting time</p> Signup and view all the answers

    When should vitamin K rich foods be avoided?

    <p>During anticoagulation therapy</p> Signup and view all the answers

    What is the consequence of vitamin K deficiency in newborns?

    <p>Increased risk of haemorrhagic disease</p> Signup and view all the answers

    What is the outcome of haemorrhagic disease in 50% of affected babies?

    <p>Death</p> Signup and view all the answers

    What is the primary mechanism by which vitamin D functions in the body?

    <p>By binding to intra-cellular receptors that eventually interact with DNA</p> Signup and view all the answers

    Which of the following is a characteristic of rickets in children?

    <p>Bending of long bones and kyphosis</p> Signup and view all the answers

    What is the primary source of ergocalciferol (vitamin D2)?

    <p>Plants, fungi, and moulds</p> Signup and view all the answers

    What is the recommended daily intake of vitamin D by the NHS for adults and children over 4 years between October and March?

    <p>10 microg</p> Signup and view all the answers

    What is the primary consequence of a vitamin D deficiency in adults?

    <p>Osteomalacia</p> Signup and view all the answers

    How is cholecalciferol (vitamin D3) formed in the skin?

    <p>Through the action of UV light on 7-dehydrocholesterol</p> Signup and view all the answers

    What is the primary effect of excessive vitamin D consumption?

    <p>Hypercalcaemia</p> Signup and view all the answers

    What is the approximate intake of vitamin D that produces toxicity?

    <p>10 x RNI (100 microg)</p> Signup and view all the answers

    Study Notes

    Vitamin C (Ascorbic Acid)

    • Sources: Citrus fruits, tomatoes, berries
    • Functions:
      • Anti-oxidant nutrient
      • Hydroxylation of proline and lysine in collagen formation
      • Reduction of dietary Fe in the stomach for absorption
      • Possibly protects vitamins A, E, K from oxidation
    • Deficiency:
      • Scurvy
      • Impaired wound healing, hemorrhages, and anemia
      • Low vitamin C status in the elderly, alcoholics, and adolescents
      • Smokers need twice the normal intake (80 mg/day) due to increased turnover of ascorbic acid

    Fat-Soluble Vitamins

    Vitamin A

    • Sources:
      • Animal liver and fish liver oils
      • Whole milk and egg yolk
      • Plant carotenoids (mainly β-carotene) in green/yellow/orange vegetables and fruits
    • Absorption:
      • Carotenoids are cleaved to 2 retinol molecules (inefficient conversion)
      • Potency expressed as retinol equivalents (1 RE = 1 μg retinol)
    • Active forms:
      • Retinoic acid (acts as a hormone)
      • Retinal (in vision)
      • β-carotene (antioxidant)
    • Functions:
      • Controls protein synthesis
      • Acts in vision (best understood function)
    • Transport and storage:
      • From gut to liver in chylomicrons
      • From liver to tissues bound to specific retinol binding protein and pre-albumin
    • Deficiency:
      • Rarely seen in developed countries, but common in developing countries
      • Associated with inadequate protein diets
      • Affects synthesis of retinol binding protein and transport to tissues
      • Night blindness, xerophthalmia, and keratomalacia
    • Toxicity/Teratogenicity:
      • Dermatitis, hair loss, mucous membrane defects, hepatic dysfunction, thinning and fracture of long bones

    Vitamin E

    • Source:
      • Vegetable oils (especially wheat germ oil)
      • Nuts
      • Green vegetables
    • Function:
      • Prevents oxidation of unsaturated/polyunsaturated fatty acids in cell membranes and circulating lipoproteins
      • Free radical scavenging
    • Deficiency:
      • Known in animals as a cause of sterility and muscular dystrophy
      • Human deficiency: virtually unknown, except in premature, low-birth-weight infants
      • Haemolytic anemia due to fragility of red cell membranes

    Vitamin D

    • A group of similar compounds
    • Cholecalciferol (Vitamin D3) occurs naturally in animals
    • Vitamin D2 (ergocalciferol) derived from ergosterol
    • Sources:
      • Milk and dairy products
      • Fortified margarine
      • Eggs
    • Function:
      • Acts to maintain correct levels of calcium and phosphate in the blood for proper bone mineralization
    • Deficiency:
      • Rickets in children
      • Osteomalacia in adults
      • Muscle weakness, bone pain, and decalcification of long bones
    • Recommendations (NHS):
      • Consider taking 10 μg between October and March for adults and children over 4 years

    Vitamin K

    • Sources:
      • Green leafy vegetables
      • Milk, meat, eggs, and cereals
      • Bacterial flora of the jejunum and ileum
    • Deficiency:
      • Blood clotting is defective
      • Increased blood clotting time is rare, except in:
        • Long-term antibiotic therapy
        • Anticoagulation therapy (Warfarin)
      • Haemorrhagic disease of the newborn

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    Learn about vitamin C, its sources, functions, and deficiency symptoms, including scurvy.

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