The importance of diet and nutrition in human health and disease is well established. Basic laboratory research, clinical trials, and epidemiological studies have all contributed to our understanding of the minimum daily requirements (MDR) for both micro- and macro-nutrients necessary for survival and disease prevention. Caloric restriction experiments in a variety of species have also suggested a connection between diet and aging. However, in spite of a virtual consensus regarding the nutrients required to prevent disease, there is widespread controversy regarding the dietary composition necessary to achieve optimum health and longevity. Further complicating this picture is the increasing evidence for the importance of oxidative stress in aging and age-related disease and the anti-oxidant and anti-inflammatory benefits of phytochemicals. The result has been considerable confusion among "experts" in the field about what and how much people should be eating and whether dietary supplementation is necessary or appropriate. We propose that the answers to these questions may be very different for different people. Although people are similar in their general nutritional requirements, considerable individual variability exists with respect to personal tastes, lifestyles, eating habits, food availability, cooking practices, nutrient absorption, environmental stress, and other factors that make the "one diet fits all" approach impractical. A more direct approach is to monitor a combination of nutrition-related parameters and outcomes (such as serum nutrient levels, oxidative stress, body composition, and health risk indicators) and modify nutritional intake in a targeted fashion to correct specific imbalances as they are detected. The result is a program of diet and supplementation that is customized to the specific needs of each individual patient with the goal of achieving intake of the ideal combination of nutrients that will produce optimal health and longevity.