Oxidative Stress

What Is Oxidative Stress?

Oxidative stress occurs when there is an imbalance between the production of reactive oxygen species (ROS) — also called free radicals — and the body's capacity to neutralize them with antioxidant defenses. Free radicals are highly unstable molecules that contain unpaired electrons; they seek to stabilize themselves by stealing electrons from cellular components such as DNA, proteins, and lipid membranes, causing chain reactions of molecular damage.

A degree of ROS production is normal and even necessary: the immune system uses them to destroy pathogens, and they serve as signaling molecules in cell growth pathways. Problems arise when ROS production chronically exceeds antioxidant capacity, damaging tissues and contributing to aging and numerous chronic diseases.

Sources of Free Radicals and Antioxidant Defense

Free radicals are generated both endogenously (by mitochondrial respiration, immune activation, and enzymatic reactions) and exogenously (by UV radiation, air pollution, cigarette smoke, alcohol, and pesticide exposure). The body's primary antioxidant enzymes — superoxide dismutase, catalase, and glutathione peroxidase — require dietary minerals as cofactors:

• Superoxide dismutase: requires manganese, copper, and zinc
• Catalase: requires iron
• Glutathione peroxidase: requires selenium

Dietary antioxidants such as vitamins C and E, beta-carotene, and polyphenols complement these enzymatic systems by directly scavenging free radicals.

Dietary Strategies to Reduce Oxidative Stress

Consuming a diverse range of colorful plant foods is the most practical approach to increasing antioxidant intake. The ORAC (Oxygen Radical Absorbance Capacity) scale, though imperfect, illustrates why variety matters: spices like cloves and cinnamon rank extraordinarily high, while everyday foods like blueberries, artichokes, and kidney beans provide substantial antioxidant loads accessible in normal portions. Vitamin E (15 mg per day for adults) from nuts, seeds, and wheat germ protects cell membranes from lipid peroxidation. Vitamin C (75–90 mg per day) regenerates oxidized vitamin E and is concentrated in citrus fruits, bell peppers, and kiwifruit. Selenium (55 mcg per day), found in Brazil nuts, seafood, and whole grains, is critical for glutathione peroxidase activity. Limiting processed foods, reducing alcohol intake, and not smoking significantly reduce exogenous ROS burden.