The biochemistry of antioxidants revisited.

Biochemical relationships between oxidative stress, antioxidant nutrients, and chronic diseases are complicated and often conflicting. Basic research supports the concept that reactive oxygen species precipitate changes that result in oxidative damage to lipid, protein, and DNA biomolecules. Oxidative stress is implicated in the development of cancer, cardiovascular disease, diabetes, sepsis, various eye diseases, and neurologic conditions. Supplementation with antioxidant nutrients seems plausible to counter the effects of oxidative stress, but the preferred mode of delivery for these nutrients may be through the patient's diet rather than as supplements to the diet. In fact, evidence supporting consumption of at least 5 servings of fruits and vegetables continues to grow. To better understand the role of antioxidant nutrients in disease promotion or prevention, this review will discuss basic nutritional biochemistry relating to oxidative stress and antioxidant defense systems, followed by a discussion of the metabolism (vitamins E, C, A) and interrelationships of select antioxidant nutrients.