Human NutritionEdit
Human nutrition is the science of how the body uses food to produce energy, build and repair tissues, and regulate biological processes. It encompasses biochemistry, physiology, epidemiology, and public health to understand what people should eat, how their bodies process those nutrients, and how dietary patterns influence health outcomes over a lifetime. Nutrition guidance translates laboratory findings into practical recommendations for individuals and populations, while also considering culture, economics, and environment.
Across cultures and histories, nutrition has been shaped by available foods, farming practices, and evolving scientific methods. Modern nutrition science seeks to balance energy intake with expenditure, ensure adequate intake of essential nutrients, and minimize risks from overconsumption or deficiency. It also examines how food systems, dietary choices, and policy interact to affect health on a broad scale.
Macronutrients
carbohydrates
Carbohydrates are a major energy source for the brain and body. They range from simple sugars found in fruit and sweets to complex starches and dietary fibers in grains, legumes, vegetables, and whole fruits. In nutrition practice, 4 kilocalories per gram is the typical energy yield used for planning, though the metabolic effects of different carbohydrate sources can vary. Dietary fibers, while not a primary energy source, contribute to digestive health and may influence metabolic risk. Public guidance often emphasizes choosing minimally processed carbohydrate sources rich in fiber and nutrients, while limiting added sugars. For more on the topic, see carbohydrates.
proteins
Proteins supply amino acids needed for tissue maintenance, enzymatic reactions, immune function, and multiple other biological roles. Adults typically require approximately 0.8 grams of protein per kilogram of body weight per day, with higher needs during growth, pregnancy, and certain illness or athletic training. The quality and completeness of protein sources—animal versus plant-based, and the presence of all essential amino acids—are considerations in dietary planning. See protein for a detailed overview of amino acids and protein requirements.
lipids (fats)
Lipids provide a dense energy source and are necessary for cell structure, hormone production, and the absorption of fat-soluble vitamins. Fatty acids come in saturated, monounsaturated, polyunsaturated, and trans forms, each with distinct health associations. Modern dietary guidance typically recommends limiting saturated fats and avoiding trans fats, while encouraging sources of unsaturated fats such as fish, nuts, seeds, and olive oil. Essential fatty acids cannot be synthesized by the body and must be obtained from the diet. For a broader discussion of fats, see lipids (commonly referred to as fats).
Micronutrients and hydration
vitamins
Vitamins are organic compounds required in small amounts for a wide range of biological processes, including energy metabolism, vision, immunity, and blood formation. They must be consumed regularly because most cannot be synthesized in sufficient quantities by the body. Diets that emphasize a variety of fruits, vegetables, fortified foods, and appropriate supplements when indicated can help prevent deficiencies. See vitamin for a catalog of individual vitamins and their roles.
minerals
Minerals such as iron, zinc, calcium, iodine, and potassium support oxygen transport, bone health, fluid balance, and enzyme activity. Deficiencies or imbalances can lead to health problems across life stages. Dietary sources include meat, dairy, fortified foods, whole grains, and leafy greens. See mineral for a deeper look at essential minerals and their functions.
water and hydration
Hydration is fundamental to physiological processes, including circulation, temperature regulation, and waste elimination. Fluid needs depend on climate, activity, health status, and diet. See water and hydration for more detail.
Energy balance, metabolism, and health outcomes
Energy balance hinges on the relationship between caloric intake and energy expenditure. Basal metabolic rate (the energy needed at rest) plus activity and the thermic effect of food determine total daily energy expenditure. Individual variation in metabolism, body composition, and genetics means that optimal intakes are not identical for everyone. See basal metabolic rate and metabolism for foundational concepts.
Nutrition also intersects with disease risk. Diet influences cardiovascular health, metabolic disorders, cancer risk, bone health, and immune function. Observational studies and randomized trials contribute to evolving guidelines, with recommendations often emphasizing overall patterns—such as emphasizing nutrient density, portion control, and moderation—over single nutrient targets. See cardiovascular disease and cancer for disease-specific links to nutrition, and dietary guidelines for Americans for policy-level guidance.
Nutrition across the life cycle and in specialized contexts
pregnancy, infancy, and childhood
Nutritional needs change across life stages. Adequate intake during pregnancy supports fetal development, while infancy and early childhood require attentive nourishment to support growth. Iron, iodine, folate, vitamin D, calcium, and essential fatty acids frequently feature in stage-specific recommendations, alongside safe and appropriate feeding practices. See pregnancy and infant nutrition for more detail.
adolescence and adulthood
Growing adolescents and adults encounter periods of rapid change in body composition and metabolism, making tailored dietary planning important. Emphasis often includes adequate protein, calcium, iron (in menstruating populations), and nutrient-dense food choices that support long-term health. See adolescence and adult nutrition for further discussion.
aging and longevity
Aging affects nutrient needs, absorption, and metabolism. Diets that support bone health, cognitive function, and cardiovascular health are topics of ongoing research and debate, with attention to practicality and quality of life in later years. See elderly nutrition and gerontology for related material.
Diet quality, patterns, and policy
Dietary patterns reflect cultural preferences, taste, and access to food. Common patterns studied in nutrition science include the Mediterranean, DASH (Dietary Approaches to Stop Hypertension), plant-based, and traditional regional diets. These patterns are examined for their nutrient density, sustainability, and health associations. Policy frameworks and guidelines—such as dietary guidelines for Americans or national nutrition programs—aim to promote healthful choices while considering cultural and economic realities. For a discussion of dietary patterns, see dietary pattern and public health nutrition.
Food systems, fortification, and supplementation also shape nutrient intake. Fortified foods can help address common deficiencies in populations, while supplements may be appropriate for certain individuals under medical guidance. See food fortification and nutritional supplement for more information.
Controversies and debates (neutral overview)
Nutrition science includes ongoing debates about how best to translate evidence into practice. Key areas of discussion include:
Macronutrient distribution: The optimal balance of carbohydrates, fats, and proteins remains a topic of study, with different patterns proposed for health, performance, and disease prevention. See dietary protein and lipids for nuanced discussions of each macronutrient.
Sugar and refined carbohydrates: There is debate about how strongly added sugars and refined grains influence metabolic health in different populations, and how to balance dietary enjoyment with health risks. See added sugar and glycemic index for related concepts.
Animal-based vs plant-based diets: Researchers and policymakers explore health, environmental, and sustainability considerations of various dietary patterns, including the role of animal products and the viability of plant-forward approaches. See vegetarianism and meat consumption for related topics.
Nutrient supplementation: The value and limits of dietary supplements are debated, with consensus that supplements can help certain groups but are not a substitute for a varied diet. See dietary supplement and multivitamin.
Personalization and precision nutrition: Emerging evidence supports tailoring advice to genetics, microbiome, and lifestyle, but translating this into broad guidelines remains a work in progress. See nutrigenomics and personalized nutrition for related discussions.
Public health policy and communication: How best to convey nutrition guidance to diverse populations, and how to balance paternalism with autonomy, is a continuing conversation in public health. See public health and risk communication for context.