Oxidative stress is an imbalance between the production of reactive oxygen species and the body’s antioxidant defenses. Reactive oxygen species, including free radicals, are highly reactive molecules generated during normal metabolism, inflammation, exposure to pollutants, radiation, some drugs and unhealthy lifestyle factors such as smoking and poor diet.

At controlled levels, these molecules play useful roles in cell signaling and immune defense. Problems arise when their production overwhelms antioxidant systems like glutathione, superoxide dismutase, catalase and various dietary antioxidants. Excess oxidative activity can damage lipids in cell membranes, proteins, and DNA. Over time this contributes to cellular dysfunction, tissue injury and chronic disease.

Research links oxidative stress to cardiovascular disease, diabetes, neurodegenerative disorders such as Alzheimer’s and Parkinson’s disease, cancer development and progression, chronic kidney disease, lung conditions, skin aging and eye diseases like cataracts and macular degeneration. It also plays a role in complications of obesity and metabolic syndrome, and in the decline of physiological functions with aging.

The body attempts to maintain redox balance through endogenous antioxidants and repair systems. Diets rich in fruits, vegetables, whole grains, nuts and other plant foods provide vitamins C and E, carotenoids and polyphenols that can support these defenses. Regular physical activity, good sleep, and avoidance of tobacco and excessive alcohol also influence oxidative status, though extremely intense exercise without recovery can transiently increase oxidative stress.

Clinical trials of antioxidant supplements have shown mixed and sometimes disappointing results, highlighting that simply adding high dose isolated antioxidants does not straightforwardly reverse oxidative damage. Current research emphasizes maintaining overall redox balance rather than eliminating reactive oxygen species entirely.