ABSTRACT
High altitude is another example of an extreme environment, char acterized by cold temperatures, hypobaric hypoxia, increased expo sure to solar radiation, aridity, and low biomass. Due to such stress ors, travel to high altitude enhances oxidative stress, arising from maladaptive biological responses to low oxygen pressure and in creased exposure to ultraviolet (UV) radiation (Askew, 2002). Reac-
tive oxygen species (ROS) and free radicals are key mediators in the pathogenesis of several chronic diseases, including cardiovascular disease (CVD). Similar to the Inuit, Tibetan highlanders have had to rely on a high-meat diet virtually devoid of fruits and vegetables due to poor plant-growing conditions. Unlike the Inuit, however, Tibetans rarely eat fish due to religious taboos, so are thus not exposed to the heart-protective benefits of omega-3 fatty acids. Instead, Tibetans rely on large mammals such as yaks, beef, and mutton, which are rich in saturated fats and cholesterol. Saturated fats have been linked to in creased risk of CVD due to their ability to elevate serum levels of low-density lipoprotein (LDL) cholesterol. Elevated LDL, com pounded with oxidative stress, paves the path toward atherosclerotic plaque formation and, ultimately, ischemic heart disease. Despite a saturated-fat-rich diet, low consumption of antioxidant-rich fruits and vegetables, and residence in a high-oxidative stress environment, Tibetan highlanders have a low incidence of ischemic heart disease (Fujimoto et al., 1989).
