Changes in lifestyle and a shift from a traditional to an industrialized/westernized diet has drastically increased the rates of diet-related chronic disease. This has led to an unprecedented explosion in the prevalence of obesity and being overweight, cancers, and chronic and metabolic diseases. The physiological mechanism of action of nutritional compounds is closely associated with their ability to recognize and modulate specific cellular enzymes or to affect the cell redox state. The identification of these targets is essential to recognize the mechanisms of action of nutritional compounds and their direct or indirect effects on cellular processes and functions in physiological and pathological conditions.