Oxygen is an essential 'nutrient' for most organisms. Paradoxically, however, oxygen damages key biological sites. This has led to oxygen being referred to as a double-edged sword. The beneficial side of oxygen is that it permits energy-efficient catabolism of fuel by acting as the ultimate electron acceptor within mitochondria. During aerobic respiration, an oxygen atom accepts two electrons, forming (with hydrogen) harmless water. The less friendly side of oxygen is the unavoidable and continuous production of partially reduced oxygen intermediates within the body. These 'free radicals' (reactive oxygen species; ROS) are more reactive than ground-state oxygen and cause oxidative changes to carbohydrate, DNA, lipid, and protein. Such changes can affect the structures and functions of macromole-cules, organelles, cells, and biological systems. This induces oxidant stress if allowed to proceed unopposed.

The human body is generally well equipped with an array of 'antioxidative' strategies to protect against the damaging effects of ROS. Our endogenous antioxidants are inadequate, however, as we are unable to synthesize at least two important antioxidant compounds, vitamin C and vitamin E. Ingestion of these, and perhaps other, antioxi-dants is needed to augment our defenses and prevent or minimize oxidative damage. In this article, the causes and consequences of oxidant stress and the types and action of antioxidants will be described, the source and role of dietary antioxidants will be discussed, and current evidence relating to dietary antioxidants and human health will be briefly reviewed.

The Most Important Guide On Dieting And Nutrition For 21st Century

The Most Important Guide On Dieting And Nutrition For 21st Century

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