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Differentiating Antioxidant Roles in Foods versus Health

Differentiating Antioxidant Roles in Foods versus Health. Ting Qi. Antioxidants in Foods. Usage in foods to protect oxidative degradation and premature loss of quality Scavenging of free radicals Chelating prooxidative metals Quenching singlet oxygen

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Differentiating Antioxidant Roles in Foods versus Health

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  1. Differentiating Antioxidant Roles in Foods versus Health Ting Qi

  2. Antioxidants in Foods • Usage in foods to protect oxidative degradation and premature loss of quality • Scavenging of free radicals • Chelating prooxidative metals • Quenching singlet oxygen • Effects on food quality demonstrated through various methods an assays • Hydrogen atom transfer (HAT) • Electron transfer (ET)

  3. From Food to Health • Positive effects on food quality  protect human cells from oxidation  prevent chronic diseases • Cancer • Atherosclerosis • Cataract • Antioxidant capacity of food measured in vitro  heath benefits on the cellular level • Source of energy and building blocks  “functional ingredients” with “health” attributes E Becker, el alANtioxidant evaluation protocols: Food quality or health effect.Eur Food Res Technol (2004)219:561-571.

  4. Cell Cultures vs. Physiological Conditions • Types and rates of nutrient and oxygen supply and metabolite removal • Endocrine environment • Hormone patterns and kinetic change • Antibiotic environment • Penicillin, streptomycin • Lipid environment • Phospholipid composition • Concentrations of constituents in the fluid • What happens in a Petri dish may not happen in people

  5. Contradictions in in vivo studies • Vitamin C & E - decrease risk of some chronic diseases? • Tocopherol - no benefit in mortality or decreased risk of cardiovascular death? • Beta-carotene, vitamin A & E – increase mortality?

  6. Contradictions in in vivo studies G Bjelakovic et al. Mortality in randomized trials of antioxidant supplements. JAMA 2007;297(8):842-857.

  7. Evaluating the Antioxidant Capacity in Foods • HAT assays • ORAC • TRAP • ET assays • FRAP • CUPRAC • Folin-Ciocalteu • Prediction for positive health effect?

  8. Evaluating the Antioxidant Capacity in vitro E. Niki. Assessment of Antioxidant Capacity in vitro and in vivo Free Radical Biology & Medicine 49 (2010) 503-515.

  9. Evaluating the Results of in vivo Intervention Studies • Dosage and Baseline Nutrient Status • Selenium: U-shaped dose-response curve between the supply and risk of cancer • Benefit of supplementation greater in people with inadequate intake • Beta-carotene, vitamin E and selenium supplementation to 30,000 people in China with sub-optimal intake • 20% risk reduction of cancer of the stomach • 10% decrease in total morality • Same treatment administered at the same dose does not necessarily benefit the overall population

  10. Evaluating the Results of in vivo Intervention Studies • Synergism antioxidants • Vitamin C & E • Integrated together with other compounds • Regeneration of lipoohilic alpha-tocopherol by water soluble ascorbic acid by H donation at membrane-water interface • Additional properties in complex systems • Multi-causal origin of chronic disease  single antioxidant may not be effective • Time • Slow evolvement of chronic nutrition-related diseases  intervention may take a long time to be effective • Folic acid study – 10 years E Becker, el alANtioxidant evaluation protocols: Food quality or health effect.Eur Food Res Technol (2004)219:561-571.

  11. Evaluating the Results of in vivo Intervention Studies • Chemistry • The binding status of a chemical determines its physiology • L-selenomethionine vs. selenite • Stereochemistry of vitamin E • Bioavailability • GI absorption • Chemical diversity • Conjugated forms • Transported, distributed, retained

  12. Conclusion and Future • Gap between antioxidative effects in vitro a compared to in vivo • No simple relationship between antioxidant capacity in foods and health benefits • Studies in absorption, nutrikinetics, nutridynamics, mechanism • View the effects of antioxidants in human body critically and scientifically based on sound research data • Health claims based on generally accepted scientific data, especially in human studies of target group

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