chap 10 pt 2

NTR 306: Fundamentals of Nutrition - Study Notes

Chapters 10 & 11: Vitamins

General Overview of Vitamins

  • Types of Vitamins

    • Water-Soluble Vitamins:

      • B-Vitamins: Thiamin, Riboflavin, Niacin, Biotin, Pantothenic Acid, B6, Folate, B12

      • Vitamin C

    • Fat-Soluble Vitamins:

      • Vitamins A, D, E, K

Differences Between Fat-Soluble and Water-Soluble Vitamins

  1. Absorption:

    • Water-Soluble: Directly into blood

    • Fat-Soluble: Into lymph (with fat), then blood

  2. Transport:

    • Water-Soluble: Free/independent

    • Fat-Soluble: Need transport proteins

  3. Storage:

    • Water-Soluble: Not stored; circulate in water areas

    • Fat-Soluble: Stored in cells with fat

  4. Excretion:

    • Water-Soluble: Kidneys remove excess

    • Fat-Soluble: Not much excreted; a lot remains in the body

  5. Toxicity (with supplements):

    • Water-Soluble: Unlikely but possible

    • Fat-Soluble: Likely, especially with excess intake

  6. Requirements:

    • Water-Soluble: Frequent doses (1-3 days)

    • Fat-Soluble: Periodic doses (weeks to months)

Vitamin C (Ascorbic Acid)

  • Antioxidant:

    • Definition: Any substance in the body that significantly decreases the adverse effects of free radicals on normal physiological functions.

    • Functions:

      • Neutralizes free radicals by donating electrons.

      • Protects against artery plaque (reduces LDL oxidation, lowers blood pressure, increases HDL).

      • Inhibits cancer formation.

  • Free Radical:

    • Definition: A highly reactive, unstable molecule with one unpaired electron.

  • Iron Absorption Enhancement:

    • Vitamin C enhances the absorption of iron in the body.

Vitamin C Deficiency

  • Early Symptoms:

    • Rough, scaly skin, irritability, general weakness, fatigue, joint pain.

  • Severe Symptoms:

    • Scurvy, swollen legs, easily bruised skin, loose teeth, dry brittle hair, anemia, swollen bleeding gums, non-healing wounds.

    • Historical context: Scurvy was prominent among sailors in the 1500-1800s.

  • First Clinical Trial on Scurvy (James Lund, 1747):

    • Foods tested include cider, sulphuric acid, sea-water, garlic, mustard seed, horseradish, vinegar, and oranges & lemons.

    • British Navy sailors referred to as 'limeys' due to the inclusion of limes in their diet to prevent scurvy.

Vitamin C Recommendations & Habitual Intake

  • Recommended Dietary Allowance (RDA) and Upper Limit (UL):

    • Males: RDA = 90 mg/d, UL = 2000 mg/d, Habitual Intake = 105 mg/d

    • Females: RDA = 75 mg/d, Habitual Intake = 84 mg/d

  • Toxicity Effects:

    • GI distress, diarrhea and can become pro-inflammatory.

  • Groups at Higher Risk of Deficiency:

    • Smokers, individuals under additional stressors like infections, burns, medications.

Vitamin C Food Sources

  • Vulnerabilities in preparation:

    • Heat sensitivity, water-soluble leaching during cooking (prefer steaming).

Vitamin A

  • Active Forms:

    • Retinol, Retinal, Retinoic Acid (collectively referred to as retinoids): Found in animal sources.

  • Carotenoids:

    • Plant sources (precursors to vitamin A), such as beta-carotene, which can be converted to retinol in the body.

Vitamin A & Vision

  • Role in Retina:

    • Retina converts light energy into nerve impulses, containing photosensitive cells (100 million rods) that include rhodopsin (composed of Opsin & Retinal).

    • Process: Light strikes retina, retinal converts from cis-retinal to trans-retinal, generating an electrical impulse sent to the brain.

    • Retinal needs constant replenishment from diet or retinol stores; only 1/1000 of vitamin A in the body is stored in the retina.

Vitamin A Recommendations & Habitual Intake

  • RDA and UL:

    • Males: RDA = 900 µg/d, UL = 3000 µg/d, Habitual Intake = 680 µg/d

    • Females: RDA = 700 µg/d, Habitual Intake = 620 µg/d

  • Deficiency Risks:

    • Prolonged deficiency affects immune function and can cause blindness; particularly concerning in developing countries (up to 500,000 preschool children affected annually).

Vitamin A Food Sources

  • Retinoid Activity Equivalents:

    • 1 µg retinol = 12 µg beta-carotene

    • Heat- and light-stable but not water-soluble.

Vitamin D

  • Non-Essential Nutrient:

    • Synthesized from sunlight and precursor cholesterol; two dietary forms:

    • D2 (ergocalciferol): plant sources

    • D3 (cholecalciferol): animal sources and skin synthesis.

Vitamin D Synthesis and Activation

  • Activation Process:

    • Hydroxylation reactions in the liver and kidneys required to activate both forms of Vitamin D.

Vitamin D Roles in the Body

  • Functions:

    • Acts like a hormone, binds to target organs such as intestines, kidneys, and bones.

    • Enhances calcium and phosphorus absorption.

    • Mobilizes calcium and phosphorus from bones into blood when dietary intake is insufficient.

    • Enhances/suppresses activity of genes regulating cell growth, possibly protecting against certain diseases.

Vitamin D Deficiency

  • Health Implications:

    • Causes calcium deficiencies leading to conditions like Rickets (in children), Osteomalacia (in adults), and Osteoporosis (loss of calcium leading to fractures).

Vitamin D Recommendations & Habitual Intake

  • RDA and UL:

    • Males: RDA = 15 µg/d, UL = 100 µg/d, Habitual Intake = 5 µg/d

    • Females: RDA = 4 µg/d

  • Deficiency Concerns:

    • Underconsumption noted, especially due to lack of sun exposure.

Vitamin D Food Sources

  • Notable sources with mg/serving, IU/serving, and %DV:

    • Cod liver oil, trout, salmon, fortified milk, mushrooms exposed to UV light, and various cereals.

Factors Impacting Vitamin D Synthesis from Sunlight

  • Latitude: (40° N to 40° S)

  • Season: (Higher production during summer)

  • Weather Conditions: (Sunny > Rainy)

  • Time of Day: (10 am to 4 pm optimal times)

  • Sunscreen Application: (Balancing protection vs. synthesis needs)

  • Skin Pigmentation: (Less melanin increases synthesis).

Vitamin E Overview

  • Subgroups:

    • Tocopherols (with α, β, γ, δ forms) and tocotrienols.

    • α-tocopherol: Only naturally active form in the body, acts as an antioxidant.

Vitamin E Recommendations & Habitual Intake

  • RDA and UL:

    • For both genders: RDA = 15 µg/d, UL = 1000 µg/d, Habitual Intake = ~7 µg/d

  • Deficiency Risks:

    • Rare, can cause erythrocyte hemolysis and neuromuscular dysfunction.

Vitamin E Food Sources

  • Notable sources with mg/serving and %DV:

    • Wheat germ oil, sunflower seeds, almonds, and various oils and nuts.

Vitamin K Overview

  • Primary Roles:

    • Blood clotting, bone density, and potential reduction in disease risk by aiding osteocalcin binding to bone-forming minerals.

Vitamin K Recommendations & Habitual Intake

  • Recommendations:

    • Males: AI = 120 µg/d; Females: AI = 90 µg/d

    • No UL established; found in both food and non-food sources (GI bacteria synthesis insufficient).

Vitamin K Food Sources

  • Notable sources with mg/serving and %DV:

    • Natto, collards, turnip greens, spinach, kale, broccoli, and various oils.

Summary & Discussion Points

  • Discussion on how to achieve dietary requirements effectively.

  • Importance of collaborative learning on dietary patterns.

Vitamin Interactions

  • Vitamin A & E:

    • Vitamin E protects Vitamin A from oxidation and aids its absorption.

  • Vitamins A, D, K:

    • Collaborative roles in bone growth and remodeling.

  • Vitamins E & K:

    • Interaction crucial for blood clotting.

Wrap-Up

  • Upcoming topics: Major Minerals, Dietary Analysis Project Part II due 11/10.

  • Note on public health concerns regarding vitamin underconsumption across all life stages.