The human blood physiology is an active system that is closely connected with environmental and lifestyle changes, which affect such processes as erythropoiesis, coagulation, platelet activity, nitric oxide (NO) signaling system, and oxygen transport. It is a synthesis of evidence based on recent research (2020-2026) on four modulators that relate to each other physically: exercise, high-altitude hypoxia, climate change-induced high and low temperatures, and consumption of non-nutritive sugar substitutes such as erythritol. Adaptive changes that are generally observed in response to exercise and altitude are increased erythropoiesis and improved vascular functions, whereas maladaptive changes, including oxidative stress, inflammatory, and prothrombotic states, may be caused by the climate extremes and erythritol. Especially sensitive parameters of hematology, such as hemoglobin (Hb), hematocrit (Hct), platelets (PLT), red blood cell (RBC) count, and white blood cell (WBC) count, pose risks, and interconnections are possible, which increase risks in a changing climate. To give an example, workouts in the altitude or heat can increase the effects of dehydration and thrombosis, particularly with the current diets rich in erythritol. This review identifies the implications of public health to vulnerable groups (such as patients with cardiovascular risk factors), and it recommends combined exposure research. A consideration of these factors as a collective entity will enable us to inform dietary and training practices that better improve health in the face of environmental adversity.
