The typical Western diet yields a net acid load estimated to be 50 mEq/d (148). As a result, healthy adults consuming the standard US diet sustain a chronic, low-grade pathogenic metabolic acidosis that worsens with age as kidney function declines (146, 149). Virtually all preagricultural diets were net base yielding because of the absence of cereals and energy-dense, nutrient-poor foods—foods that were introduced during the Neolithic and Industrial Eras and that displaced base-yielding fruit and vegetables (147). Consequently, a net base-producing diet was the norm throughout most of hominin evolution (147). The known health benefits of a net base-yielding diet include preventing and treating osteoporosis (150, 151), age-related muscle wasting (152), calcium kidney stones (153, 154), hypertension (155, 156), and exercise-induced asthma (157) and slow the progression of age- and disease-related chronic renal insufficiency (158).
Cordain, Loren, Eaton, S Boyd, Sebastian, Anthony, Mann, Neil, Lindeberg, Staffan, Watkins, Bruce A, O'Keefe, James H, Brand-Miller, Janette
Origins and evolution of the Western diet: health implications for the 21st century
Am J Clin Nutr 2005 81: 341-354
So, perhaps while many high-protein foods have a high acid load, the net acid load, which can be brought lower by eating fruits and vegetables, is ultimately what matters.