Challenging homeostasis to define biomarkers for nutrition related health.

A primary goal of nutrition research is to optimize health and prevent or delay disease. Biomarkers to quantify health optimization are needed since many if not most biomarkers are developed for diseases. Quantifying "normal homeostasis" and developing validated biomarkers are formidable tasks because of the robustness of homeostasis and of inter-individual diversity. In this paper, we discuss the science, strategies, and technologies for measuring parameters that define individual health. The following concepts are central to define the physiology of the healthy individual: (i) responses to a challenge of homeostasis will be more informative than static homeostatic measures; (ii) processes involved in maintaining homeostasis usually are multi-factorial and require quantitative analyses of the many individual components involved; (iii) health includes a large variation in "normality" and the effects of nutritional interventions may remain hidden in this "diversity of robustness," if incompletely analyzed. Specifically, comprehensive multi-parameter ("omics") analysis may identify key parameters (biomarkers) and lead to a greater understanding of health supporting processes. Perturbation tests that accurately target aspects of the overarching drivers of health (metabolism, oxidation, inflammation, and psychological stress) may be instrumental in creating knowledge for maintaining health and preventing disease through nutrition.