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Lecture 9

HLTB 11 Lecture 9: Nutrition 9

4 Pages

Health Studies
Course Code
Thomas M S Wolever

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Chapter 9: Fat Soluble Vitamins  Vitamin A o Source: Liver, eggs, diary, yellow/orange/red fruits/veggies o Role:  visual pigment (night vision)  regulation of gene expression / cell differentiation  Skin and epithelial tissue  Immune function  Reproduction and growth o Consequence  Night blindness; xerophthalmia; Increase susceptibility to infection o Toxicity:  preformed vit A highly toxic (liver damage, birth defect)  Plant source not toxic (carotene, carotenoid)  High dose Retinol toxic (3000ug)  Acute: nausea, vomiting, headache, dizziness, blurred vision, muscle uncoordination (Artic explorers POLARBEARS LIVER)  Chronic: weight loss, Muscle/joint pain, born abnormalities, fracture, dry lips, skin rash  Teratogen: causes birth defect; pregnant woman should not eat liver o Form: Carotenoids  Retinol Retinal  Retinoic acid  Beta- Carotene  Retinal  Beta carotene is converted to retinol; conversion is inefficient o Not all beta-carotene is absorbed o Not all beta-carotene is converted to retinol  Beta-carotene circulates in the blood o Acts as ANTIOXIDANT o Reduces risk of lung cancer o Visual cycle: NIGHT blindness  Light strike the visual pigment Rhodopsin (opsin and retinal)  If low vitamin A status, Regeneration of rhodopsin is delay. Until it is reformed light cannot be perceived. o Retinoic acid binds to a receptor in the nucleus Binds to a DNAtranscription turns on, increases mRNA  increasing synthesis of protein  increases amount of protein o Vitamin A and cell differentiation: Maintains the epithelial tissue (barrier skin)  Low Vitam
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