Sound clinical nutrition practice is grounded in evidence and stimulated by research. Yet, there are unanswered questions about food-health relationships. Clinical nutrition involves the identification of nutritional disorders and the motivation to rectify them with all required care. Vitamin D health exemplifies the biomedical, societal and environmental dimensions of clinical nutrition, its science and practice. It depends most of all on access to sunshine and food and probably represents a paradigm in human health which is still at its beginning. Nevertheless, the problem of its deficiency is much more widespread and common than has been thought since it was first identified as a cause of rickets and osteomalacia. It is now known to spare no body organ or system. The problem in North-East Asia is comparable to much of the rest of the world, but the risk profile for it is exaggerated by atmospheric pollution, cultures with sun-avoidance on account of skin colour and potentially mitigated by foodstuffs like fish, eggs, organ meats and mushrooms which can partially offset sunshine-deficiency. Diagnosis requires a high index of suspicion and confirmation by biochemistry which may not be affordable. Therefore a close working relationship between public health and clinical nutritionist is essential.