Nutrition ch 9

Chapter 9: Fat Soluble Vitamins

Overview of Fat Soluble Vitamins

  • Includes Vitamins A, D, E, K

  • Requires bile and dietary fat for absorption

  • Stored in body fat, which allows for variable intake without immediate risk of deficiency

  • Increased risk of toxicity due to storage in body fat

Fat Soluble: Vitamin A

Sources of Vitamin A

  • Animal Sources (Retinoids): Liver, cod liver oil, salmon

  • Plant Sources (Carotenoids): Carrots, sweet potatoes, spinach, pumpkin, red bell pepper

Functions of Vitamin A

  • Animal Sources: Promote good vision, particularly night vision

    • Night Blindness: Trouble seeing in low light

    • Xerophthalmia: Serious eye disease due to Vitamin A deficiency

  • Plant Sources: Antioxidants that contribute to the colors in vegetables and fruits

Deficiency and Toxicity

  • Deficiency: Can lead to night blindness and permanent blindness

  • Toxicity: High intakes of carotenoids cause hypercarotenemia, resulting in a yellowish-orange skin appearance

Vitamin A Transport and Function

  • Transport: Vitamin A travels to cells via lipoproteins in the lymphatic system and blood, requiring retinol-binding protein for transport from the liver.

Forms of Vitamin A and Their Functions

  • Retinol: Circulates in blood, essential for vision.

  • Retinal: Important for vision processes.

  • Retinoic Acid: Influences gene expression and cell differentiation.

  • Carotenoids: Act as antioxidants and have biological functions.

Fat Soluble: Vitamin D

Overview of Vitamin D

  • Known as the “Sunshine Vitamin”

  • Produced in the skin via UV light exposure.

  • Conversion Process: 7-dehydrocholesterol (from cholesterol) transforms into cholecalciferol (Vitamin D) upon sunlight exposure.

  • Essential for those with limited sun exposure; often supplemented in northern climates.

  • Sunscreen use can reduce Vitamin D synthesis.

Functions

  • Essential for calcium absorption and bone health.

Sources

  • Salmon, low-fat milk, eggs.

Deficiency and Toxicity

  • Deficiency Effects:

    • Poor calcium absorption leads to:

      • Rickets in children: Bowed legs and short stature.

      • Osteomalacia in adults: Softening of bones.

  • Toxicity: Over-supplementation causes too much calcium absorption, leading to potential cardiovascular issues from calcium deposits.

Vitamin D Synthesis Process

  1. UV light converts 7-dehydrocholesterol in skin to Vitamin D3.

  2. Dietary Vitamin D travels to the liver for activation.

  3. In the liver, it transforms into 25-hydroxy vitamin D3.

  4. In the kidneys, it becomes active vitamin D (1,25-dihydroxy vitamin D3).

Role of Vitamin D in Calcium Management

  • Kidney: Active vitamin D increases calcium reabsorption and decreases loss in urine.

  • Bone: Works with PTH to release calcium into blood.

  • Intestine: Enhances dietary calcium absorption.

Fat Soluble: Vitamin E

Functions

  • Acts as an antioxidant;

  • Maintains integrity of red blood cells and nerve cells.

Sources

  • Nuts, seeds, and peanuts.

Deficiency

  • Hemolytic anemia in newborns, requiring high Vitamin E formula; rare in adults.

Antioxidant Function of Vitamin E

  • Neutralizes damaging free radicals by donating an electron.

  • Can be restored by Vitamin C, which gives an electron back to Vitamin E.

Fat Soluble: Vitamin K

Functions

  • Major role in blood clotting; essential for production of prothrombin.

Sources

  • Leafy green vegetables (spinach, kale).

Deficiency

  • Common in newborns; reduced blood clotting ability.

  • Newborns receive a Vitamin K shot shortly after birth to prevent deficiency.

Vitamin K and Blood Clotting

  • Involves a series of reactions that require Vitamin K to form prothrombin and fibrinogen, essential for blood clot formation.

Who Needs Supplementation?

Recommendations for Dietary Supplements

  • Diets of 1200 kcal: Multivitamin-multimineral recommended.

  • Vegans: Need supplements for Vitamin B12.

  • Infants and Children: Recommendations for fluoride, vitamin D, iron.

  • Women of Childbearing Age: Folate supplementation crucial.

  • Pregnant Women: Iron, folic acid, multivitamins recommended.

  • Older Adults: B12 and calcium supplementation suggested due to absorption issues.

  • People with Dark Skin: May require Vitamin D supplements.

  • Individuals with Medical Conditions: May need specific nutrient supplementation due to dietary restrictions.

  • Cigarette Smokers: Higher vitamin C and possibly E requirements due to increased oxidative stress.