Nutrition material 10

Chapter 10: Nutrients Involved in Antioxidant Function and Vision

Introduction to Antioxidants

• Mika, a college student, receives care packages of healthful foods and supplements from her mom, including antioxidant vitamins.

• Discussion points:

  • Does Mika's lifestyle (junk food, smoking) counteract the benefits of her antioxidant vitamins?

  • Purpose of antioxidants and their role in health risks.

What Are Antioxidants?

• Definition: Compounds that protect cells from oxidative damage.

• Oxidation: A chemical reaction where atoms lose electrons.

  • During metabolic reactions, loss of electrons is called oxidation.

  • Stable atoms have an even number of electrons; loss results in unpaired electrons, leading to instability.

• Free Radicals: Highly unstable atoms/molecules formed during oxidation, can cause cellular damage.

Sources and Causes of Free Radicals

• Common causes:

  • Energy metabolism processes (formation of ATP).

  • Immune responses (inflammation).

  • Environmental toxins (UV rays, pollution, tobacco).

• Free radicals can damage cell membranes, lipoproteins, proteins, and DNA.

Impacts of Free Radicals

• Damage to cell membranes compromises cellular integrity, leading to:

  • Disease progression (e.g., cardiovascular disease, cancer).

  • Inflammation and blood clots contributing to serious health risks (heart attacks, strokes).

How Antioxidants Assist the Body

• Mechanisms:

  1. Independent Action: Antioxidant vitamins donate electrons to stabilize free radicals (e.g., Vitamin E).

  2. Mineral Involvement: Minerals act as cofactors within antioxidant enzyme systems, converting free radicals to less damaging substances and recycling antioxidant vitamins.

     • Example Enzymes: Superoxide dismutase, Catalase, Glutathione peroxidase.

  3. Phytochemical Role: Compounds like beta-carotene stabilize free radicals.

Key Antioxidants

• Vitamins:

  • Vitamin E: Fat-soluble, protects cell membranes, key antioxidant function through donating electrons.

  • Vitamin C: Water-soluble, aids in collagen synthesis, acts as an antioxidant, enhances iron absorption.

• Minerals:

  • Selenium, copper, iron, zinc, manganese involved in antioxidant functions.

• Phytochemicals: Compounds promoting health, aiding in free radical stabilization (e.g., beta-carotene).

Recommended Intakes and Dietary Sources

• Vitamin E: RDA of 15 mg alpha-tocopherol; found in nuts, seeds, green leafy vegetables.

• Vitamin C: RDA of 90 mg for men, 75 mg for women; abundant in fruits and vegetables.

• Selenium: RDA of 55 mg; found in animal products, Brazil nuts, and grains (variable due to soil content).

Vitamin E's Specific Functions

• Functions: Protects PUFAs and cellular components; antioxidant, anticoagulant properties, and promotes immune function.

• Toxicity: Mild disorders like nausea at high intakes; impacts on cardiovascular health noted with excessive supplementation.

Vitamin C's Unique Properties

• Vital for collagen synthesis, immune function, and acting as an antioxidant.

• Important in reducing risk of chronic diseases (declining immune function, scurvy).

Role of Minerals in Antioxidant Systems

• Selenium: Important in glutathione peroxidase; linked to Keshan disease when deficient.

• Copper, iron, zinc, manganese: Cofactors in antioxidant enzyme systems, enhance immune and metabolic functions.

Beta-Carotene Overview

• Not essential but acts as a precursory carotenoid for Vitamin A.

• Antioxidant properties noted, weak compared to vitamin E but beneficial for UV protection and immune support.

• Food sources: Carrots, sweet potatoes, dark leafy greens.

Functions of Vitamin A

• Essential for vision; forms retinal and supports eye health by aiding in rhodopsin composition.

• Contributes to cell differentiation, reproduction, and growth; deficiency can lead to night blindness or xerophthalmia.

Cancer and Free Radicals

• Cancer characterized by uncontrolled cell growth, influenced by oxidative damage, genetic mutations, and lifestyle factors (e.g., tobacco use, diet).

• Antioxidants may reduce cancer risk by neutralizing free radicals, inflammation reduction, and immune support.

• Epidemiological studies suggest diets rich in fruits, vegetables, and antioxidants contribute to lower cancer rates.

Cardiovascular Disease (CVD)

• CVD is the leading cause of death; influenced by diet, antioxidants may lower risks.

• Mechanisms of protection from antioxidants in reducing inflammation, improving vessel health, and preventing clots.

Phytochemicals and Health

• Emerging research supports phytochemicals' roles beyond basic nutrition, involving detoxification processes, disease pathway interference, improved medication efficacy.

• Recommended to focus on consuming whole foods, particularly plant-based sources, for maximum health benefits.