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Fat-Soluble Vitamins in Nutrition

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  • Which vitamins are classified as fat-soluble?
    Vitamins A, D, E, and K are fat-soluble vitamins.
  • What is required for absorption of fat-soluble vitamins?
    They require bile and dietary fat for absorption.
  • How are fat-soluble vitamins transported in the body?
    They are transported with fats through the lymphatic system in chylomicrons before entering the blood.
  • Where are fat-soluble vitamins stored in the body?
    They are stored in body fat and are not easily excreted.
  • What are the two forms of Vitamin A found in the diet?
    Vitamin A is found as preformed vitamin A from animal products and as precursor carotenoids from plant foods.
  • What are retinoids and carotenoids in relation to Vitamin A?
    Retinoids are preformed vitamin A (retinol, retinal, retinoic acid), while carotenoids are plant pigments some of which are vitamin A precursors like beta-carotene.
  • What is the key role of Vitamin A in vision?
    Vitamin A is part of rhodopsin, a visual pigment essential for night vision.
  • What are symptoms of Vitamin A deficiency?
    Symptoms include xerophthalmia (night blindness), abnormal jaw growth in children, and increased infections.
  • What are risks of Vitamin A toxicity?
    Excess Vitamin A can cause nausea, vomiting, headache, dizziness, blurred vision, birth defects, liver damage, and bone fractures.
  • How does Vitamin A affect gene expression?
    Vitamin A regulates gene expression involved in cell differentiation and growth, ensuring healthy eyes and epithelial tissue.
  • How is Vitamin D synthesized in the body?
    Vitamin D is made in the skin with exposure to ultraviolet (UV) light and activated in the liver and kidneys.
  • What is the main function of Vitamin D?
    Vitamin D maintains normal blood levels of calcium and phosphorus essential for bone health and muscle function.
  • What happens when blood calcium is low in relation to Vitamin D?
    Low calcium stimulates parathyroid hormone (PTH) release, which activates Vitamin D to increase calcium absorption.
  • What are symptoms of Vitamin D deficiency?
    Deficiency causes rickets in children (bowed legs) and osteomalacia in adults (soft bones and muscle pain).
  • What are sources of Vitamin D in the diet?
    Sources include liver, egg yolks, oily fish (e.g., salmon), and fortified foods.
  • What is the main antioxidant form of Vitamin E absorbed by the body?
    The main form is alpha-tocopherol.
  • What is the primary function of Vitamin E?
    Vitamin E acts as an antioxidant protecting lipids in cell membranes and lipoproteins.
  • What are symptoms of Vitamin E deficiency?
    Deficiency can cause hemolytic anemia in infants and rare nerve damage in adults.
  • What is the role of Vitamin K in the body?
    Vitamin K is essential for synthesis of blood-clotting proteins and proteins involved in bone formation.
  • What causes Vitamin K deficiency symptoms?
    Deficiency leads to abnormal blood clotting, bruising, uncontrolled bleeding, and reduced bone density.
  • How does warfarin affect Vitamin K function?
    Warfarin inhibits the formation of active Vitamin K, preventing blood clotting.