The Biology of Superfoods and Antioxidants

All living organisms contain antioxidant enzymes and chemicals. These work together to prevent oxidative damage to cellular components such as DNA, proteins and lipids. In cells, the oxidising agents that cause this damage are called reactive oxygen species. In general, antioxidant systems either prevent these reactive species from being formed, or remove them before they can damage vital components of the cell.

Oxidative damage

Without antioxidants in our diet, we suffer greater rates of oxidative damage. This is when the reactive oxygen produced in cells include hydrogen peroxide (H₂O₂), hypochlorous acid (HOCl), and free radicals such as the hydroxyl radical (·OH) and the superoxide anion (O₂⁻). These molecules are unstable and highly reactive, and can damage cells by starting chemical chain reactions such as lipid peroxidation, or by oxidising DNA or proteins. Damage to DNA can lead to mutations and cancer if not reversed by DNA repair mechanisms. Damage to proteins can cause enzyme inhibition and denaturation.

Applications in nutrition and medicine

Health preservation

Antioxidants are chemicals that reduce oxidative damage to cells and biomolecules. Researchers have found a high correlation between oxidative damage and the occurrence of disease. For example, low density lipoprotein (LDL) oxidation is associated with cardiovascular disease. The process leading to atherogenesis, atherosclerosis, and cardiovascular disease is complex, involving multiple chemical pathways and networks, but the precursor is LDL oxidation by free radicals, resulting in inflammation and formation of plaques.

Research suggests that consumption of antioxidant-rich foods reduces damage to cells and biochemicals from free radicals. This may slow down, prevent, or even reverse certain diseases that result from cellular damage, and perhaps even slow down the natural ageing process. This is the basis for the free-radical theory of ageing.

Some of the reactions in the body that produce free radicals involve metal ions. Some antioxidants, such as the tannins in walnuts and tea, chelate (wrap around) metal ions. This not only reduces the formation of ion-dependent free radicals, but also prevents the metal ions from oxidizing cells and biochemicals directly.

Some studies suggest that by destroying free radicals and reducing cellular damage, antioxidants in the diet can have positive health effects, such as preventing macular degeneration (studied in the Age-Related Eye Disease Study); maintaining the immune system; potentially preventing neurodegeneration due to oxidative stress; preventing DNA damage; and lowering the risk of cardiovascular disease. Any specific antioxidant may perform only a small fraction of these functions. The mixed results from controlled studies using antioxidant vitamins suggest that other antioxidant substances in fruit and vegetables at least partially explain the better health of those who consume more fruit and vegetables. Dietary antioxidants are not the primary antioxidant inside the body, and there are still many questions as to how polyphenols and other dietary antioxidants protect cells and biochemicals from oxidation. Some antioxidants preserve, or even recycle, other antioxidants such as vitamin E.

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