SCOPE:Research is limited on diet challenges to improve health. A short-term, vegan protein diet regimen nutritionally balanced in macronutrient composition compared to an omnivorous diet was hypothesized to improve metabolic measurements of blood sugar regulation, blood lipids, and amino acid metabolism. METHODS AND RESULTS: This randomized, cross-over, controlled vegan verses animal diet challenge was conducted on 21 (11 female,10 male) healthy participants. Fasting plasma was measured during a 3-day diet intervention for clinical biochemistry and metabonomics.