What Are Humans Designed to Eat? An IOM Systems Medicine Framework for Dietary Compatibility, Nutrient Density, and Toxicological Burden

Modern dietary debates remain highly polarized among competing nutritional paradigms, including low-fat, Mediterranean, plant-based, vegan, low-carbohydrate, ketogenic, and animal-based dietary models. Despite decades of nutritional guidelines and extensive epidemiological research, chronic diseases—including obesity, type 2 diabetes mellitus (T2DM), atherosclerotic cardiovascular disease (ASCVD), autoimmune disorders, cancer, and neurodegenerative diseases—continue to rise globally. These trends raise an important question: are prevailing nutritional frameworks adequately aligned with human physiology, metabolic biology, and long-term systems resilience?This paper proposes an Integrative Orthomolecular Medicine (IOM) Systems Medicine framework for evaluating human diets based not solely on caloric intake or macronutrient composition, but on broader biological principles including metabolic compatibility, metabolic flexibility, nutrient density and bioavailability, mitochondrial energetics, inflammatory regulation, biological barrier integrity, oxidative-reduction balance, and cumulative toxicological burden.We first examine evolutionary and physiological foundations of human nutrition, emphasizing omnivorous adaptation, fuel-switching physiology, fasting metabolism, and the evolutionary importance of energetic resilience during periods of food scarcity, migration, hunting, and prolonged physical exertion. Particular attention is given to the human capacity for metabolic flexibility—the ability to transition between glucose utilization, fatty acid oxidation, and ketone metabolism according to energetic demands and nutrient availability. We propose the Energetic Resilience Principle, which suggests that nutritional systems should be evaluated not solely according to glycemic control, but also according to their effects on mitochondrial energetics, fuel adaptability, endurance capacity, fasting tolerance, and long-term physiological resilience. Particular attention is also given to the absence of a clearly established minimum dietary carbohydrate requirement in the presence of adequate protein and fat intake.We then compare major dietary models—including the Standard American Diet (SAD), Mediterranean, plant-based and vegan, low-carbohydrate, ketogenic, and carnivore/elimination-based approaches—across multiple domains relevant to metabolic health and systems biology. Particular attention is given to the potential consequences of chronic dependence on highly refined, continuously fed, hyperinsulinemic metabolic states, including impaired metabolic flexibility, mitochondrial stress, oxidative imbalance, and reduced physiological adaptability.Special attention is given to the nutritional and toxicological characteristics of both plant- and animal-derived foods. While plant foods provide fiber, phytonutrients, vitamins, and numerous bioactive compounds, they may also contain naturally occurring defense compounds such as lectins, oxalates, phytates, alkaloids, and gluten-related proteins, in addition to agricultural contaminants including pesticides, herbicides, and microplastics. Conversely, animal-derived foods may bioaccumulate persistent fat-soluble pollutants and environmental contaminants. The paper further proposes that plant-heavy and animal-heavy dietary systems may differ in dominant toxicological exposure profiles, including relative tendencies toward water-soluble agricultural contaminants and plant defense compounds versus fat-soluble bioaccumulated environmental pollutants. Accordingly, this paper proposes that no modern dietary system is entirely toxin-free, and that dietary strategies should instead be evaluated according to cumulative toxicological burden, nutrient sufficiency, metabolic effects, mitochondrial support, and biological compatibility.Finally, this paper proposes a hierarchical IOM Systems Nutrition framework emphasizing: • low glycemic burden, • low ultra-processing burden, • low cumulative toxicological burden from both natural and industrial exposures, • nutrient sufficiency, • metabolic flexibility, • mitochondrial support, • preservation of energetic resilience, • and long-term physiological adaptability.Within this framework, nutrition is viewed not merely as a source of calories or macronutrients, but as a systems-level regulator of mitochondrial energetics, metabolic resilience, endocrine signaling, inflammatory regulation, biological integrity, adaptive stress responses, and long-term physiological resilience. The framework proposed is intended as a comparative systems-based model for evaluating dietary compatibility with human physiology and adaptive metabolism, rather than a universal prescription for any single dietary pattern.