Diet is the single leading predictor variable for health outcomes in the modern world, both morbidities and mortality. Variations in diet quality translate into variations in the rates of heart disease, diabetes, cancer, stroke, dementia, and premature death. Diet has an enormous impact on climate, the environment, and biodiversity as well- and while these have tremendous, intrinsic value, they also impact human health monumentally, if indirectly. All of this is established fact. But even as we acknowledge the profound importance of diet to every aspect of health, public and planetary, we routinely argue over the components of diet most relevant to this aggregate influence. By doing so, we propagate the semblance of discord and dissent, obscuring the common ground, precluding common cause, and forestalling the translation of knowledge into the power of collective action. How can truth so large hide for so long in plain sight? Is our knowledge of nutrition and health genuinely in perpetual doubt, and up for grabs, as some contend? Is nutrition science fatally flawed? Are we even using science “right”? This talk will plot a path through these trees to the forest of larger, stable truths. It will explore what we know, and how we know it- arguing for the ineluctable dependence of science on sense. The argument will culminate with the case for measuring what matters routinely, so that we have some hope of managing it effectively. Diet is a vital sign; it is past time to treat it as such.