The bottom line of all these complex reactions is that ROS and RNS, while common in biological systems and often playing critical roles in the processes of life, can be dangerous. They are essential and yet, because of the way life evolved here on earth, they can also be lethal. Damage that radicals and reactive species can inflict on critical biomolecules must be repaired or damaged cells replaced (from stem cells) in order for organisms to continue to function. ROS and RNS-generated damage increases with age and damaging processes, such as underlying chronic inflammation, accumulated exposure to environmental injury from radiation, or xenobiotics. Simultaneously, the ability to repair or remove damaged biomolecules declines as well.55 This imbalance between radical induced damage and the radical defense and tissue repair mechanisms has been proposed as the mechanism leading inevitably to development of age-related diseases such as cardiovascular disease, cancers, and neurodegenerative disorders.
The fact that a number of diseases are associated with oxidative stress drives the theory that antioxidants may represent an intervention strategy in these diseases. However, current evidence from clinical research has not unequivocally substantiated these theories nor demonstrated a causal role of pro-oxidants in age-related diseases. Neither has scientific evidence proved conclusively that dietary antioxidant supplementation can prevent disease or increase longevity in humans. Thus, debate and controversy has arisen among scientists, health care professionals, and the lay public alike regarding the efficacy and wisdom of using dietary antioxidant supplementation to prevent chronic diseases and delay aging.
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