A nutrient is a substance used by an organism to survive, grow, and reproduce. The requirement for dietary nutrient intake applies to
protists. Nutrients can be incorporated into cells for
metabolic purposes or
excreted by cells to create non-cellular structures, such as
exoskeletons. Some nutrients can be metabolically converted to smaller molecules in the process of releasing energy, such as for
fermentation products (
vinegar), leading to end-products of water and
carbon dioxide. All organisms require water. Essential nutrients for animals are the energy sources, some of the
amino acids that are combined to create
proteins, a subset of
vitamins and certain
minerals. Plants require more diverse minerals absorbed through roots, plus carbon dioxide and oxygen absorbed through leaves.
Fungi live on dead or living organic matter and meet nutrient needs from their host.
Different types of organism have different essential nutrients. Ascorbic acid (
vitamin C) is essential, meaning it must be consumed in sufficient amounts, to humans and some other animal species, but not to all animals and not to plants, which are able to synthesize it. Nutrients may be
organic or inorganic: organic compounds include most compounds containing carbon, while all other chemicals are inorganic. Inorganic nutrients include nutrients such as
zinc, while organic nutrients include, among many others, energy-providing compounds and vitamins.
A classification used primarily to describe nutrient needs of animals divides nutrients into
micronutrients. Consumed in relatively large amounts (
ounces), macronutrients (
fats, proteins, water) are used primarily to generate energy or to incorporate into tissues for growth and repair. Micronutrients are needed in smaller amounts (
micrograms); they have subtle
physiological roles in cellular processes, like
vascular functions or
nerve conduction. Inadequate amounts of essential nutrients, or diseases that interfere with absorption, result in a deficiency state that compromises growth, survival and reproduction. Consumer advisories for dietary nutrient intakes, such as the United States
Dietary Reference Intake, are based on deficiency outcomes and provide macronutrient and micronutrient guides for both lower and
upper limits of intake. In many countries, macronutrients and micronutrients in significant content are required by regulations to be displayed on food product labels. Nutrients in larger quantities than the body needs may have harmful effects.
 Edible plants also contain thousands of compounds generally called
phytochemicals which have unknown effects on disease or health, including a diverse class with non-nutrient status called
polyphenols, which remain poorly understood as of 2017.
Plant nutrients consist of more than a dozen minerals absorbed through roots, plus carbon dioxide and oxygen absorbed or released through leaves. All organisms obtain all their nutrients from the surrounding environment.