ANTIOXIDANTS

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Lecture 22 HLTH 2001 2007
Antioxidants

• Overview
• Part 1
• Development of free radicals
• Oxidative Damage
• Antioxidants vs Free radicals
• Part 2
• Common types and sources of antioxidants
• Their role in fighting aging and disease

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Free radical formation and damage

• Oxidation is a normal metabolic chemical process
  in the body.
• By-products of normal cell functions are called
  "oxidative radicals" or "free radicals" or
  "reactive oxygen species" are created.
• Free radicals are unstable and highly reactive
  molecules with one or more unpaired electrons.
• They pull strongly on the electrons of other
  molecules, causing damage by destabilizing the
  molecule's electrical balance. Tend to steal
  electron from protein, lipid or DNA
• This destabilization can cause molecules to break
  apart, sometimes initiating chain-reactions of
  oxidative radical formation, thus a single
  hydroxyl radical can damage several other
  molecules

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Formation of Free Radicals

• Endogenous Factors
• normal aerobic respiration
• metabolism
• inflammation
• Exogenous factors
• Pollution
• Sunlight
• Strenuous exercise
• X-rays
• Smoking and alcohol

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Free Radicals
Polyunsaturated fatty acids
DNA and RNA
Proteins
Altered DNA and RNA
Lipid radicals
Altered Proteins
Absence of specific proteins Excess of specific
proteins
Impaired cell function Inflammatory response
Cell damage Diseases Aging
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Enzymes involved in free radical defense
start
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SOD Superoxide dismutase GSH Glutathione
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Antioxidants- what are they?

• Dietary antioxidants
• Substances typically found in foods that
  significantly decrease the adverse effects of
  free radicals
• Non nutrients
• Uric acid
• coenzyme Q10 (CoQ10, or ubiquinone)
• Phytochemicals from plants
• isoflavones, polyphenols, and flavanoids

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Antioxidants- what do they do?

• Help fight aging and disease
• Block action of free radicals by donating one of
  its electrons
• Antioxidants are stable in either form so it does
  not become a free radical itself
• See Animation on CD associated with Whitney
  Rolfes (2005) Understanding Nutrition - Chpt 11
• Also see Figure 10-15 Active Forms of Vitamin C
  (p351)

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Antioxidants- what do they do?

• Antioxidants minimize damage by
• Limiting free-radical formation
• Destroying free radicals or their precursors
• Stimulating antioxidant enzyme activity
• Repairing oxidative damage
• Stimulating repair enzyme activity

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Aging and need for antioxidants

• As we age the body is less able to control the
  destruction of free radicals so damage
  accumulates
• Dietary antioxidants can help limit the damage
• When damage is in excess the health problems
  develop

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Antioxidants
Part 2 What are good sources How they help
prevent specific diseases
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Common Antioxidants

• Key antioxidant nutrients include
• Vitamin C
• Vitamin E
• b-carotene
• Selenium

Protects skin and body fluids Can also restore
Vit E to its active form
Defends the bodys lipids
forms the active site of several antioxidant
enzymes including glutathione peroxidase
Antioxidants can be recycled
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Vitamin C (ascorbic acid)

• scavenges free radicals in the aqueous phase of
  cells
• important in muscle cells
• regenerates VITAMIN E
• Protects against LDL oxidation and raises HDL
• Improves blood pressure
• Minimizes inflammation

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Vitamin E (a -tocopherol)

• Prevents free radical mediated oxidation of
  membrane polyunsaturated fatty acids
• Protects against
• LDL oxidation
• Inflammation
• Arterial injuries
• Blood clotting
• May provide protection against heart disease but
  possibly detrimental for people who already have
  heart disease

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b carotene

• Lycopene
• a carotenoid pigment
• Food sources
• tomatoes, watermelon, pink grapefruit

• Protective against cancer
• Prostate cancer
• Protective effect 10-12 serves per week 10-12
  tomatoes or tomato product s/week

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Lycopene Levels

• Food lycopene serve lycopene
• mg/100g size per serve
• Tomato juice 9.5 1 cup 25.0
• Tomato paste 42.2 2 Tbsp 13.8
• Tomato sauce 14.1 ¼ cup 8.9
• Chilli sauce 19.5 2 Tbsp 6.7
• Tomato(raw) 3.0 1 medium 3.7
• Pink grapefruit 4.0 ½ fruit 4.9
• (raw)

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Other Dietary Antioxidants

• Other important nutrients that impact on extent
  of free radical damage
• Minerals
• iron
• copper
• zinc
• Manganese

Phytochemicals Polyphenols Flavanoids Isoflavones
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Comparison of Antioxidant levels
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What do polyphenols do?
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Which Tea is best?
Cabrera et al. 25 (2) 79. (2006) Green Tea
Beneficial Effects
Look at the scale!!
GA gallic acid EGCG epigallocatechin-3-gallate
EGCepigallocatechin ECG epicatechin-3-gallate
EC epicatechin.
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Free Radicals and CVD

• Free radicals within then arterial walls oxidize
  LDL changing the structure and function
• The oxidize LDL then accelerate the formation of
  artery-clogging plaques
• Oxidize PUFA of cell membranes which causes
  arterial walls to thicken resulting in impaired
  blood flow
• Susceptibility to such oxidative damage within
  the arterial walls is heightened by a diet high
  in saturated fat or cigarette smoke

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Antioxidants and CVD

• Antioxidants can inhibit proatherogenic and
  prothrombotic oxidative events in the artery wall
  that contribute to the atherosclerotic process
• Large clinical trials have failed to demonstrate
  a beneficial effect of antioxidant supplements on
  CVD morbidity and mortality but smaller studies
  have reported benefits on set CV endpoints
• Antioxidant supplements may slow the progression
  of atherosclerosis Huang et al 2002
• Thus AHA and ACC recommend diets rich in
  antioxidants but do not support taking vitamin
  supplements for CV health

Kris-etherton et al 2004
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Reference

• Whitney Rolfes (2005)
• Understanding Nutrition
• Chapter 11. Highlight Antioxidant nutrients in
  disease prevention

E-readers Huang et al. 2002 Effects of vitamin C
and vitamin E on in vivo lipid peroxidation
results of a randomized controlled trial. Am J
Clin Nutr 76(3), pg 549-55 Kris-etherton et al.
2004 Antioxidant Vitamin Supplements and
Cardiovascular Disease. Circulation 110(5), pg 637