nutrient
Meaning of nutrient: Food is judged by what the body can pull out of it: energy, building blocks, and the trace substances that keep reactions running.
Definition of nutrient
A nutrient is a substance obtained from food that the body uses for energy, for growth, for repair, or to keep its chemical processes running. Nutrients split into macronutrients, needed in large amounts, and micronutrients, needed in tiny amounts but no less necessary. Carbohydrate, protein, fat and water make up the first group; vitamins and minerals make up the second.
What separates a macronutrient from a micronutrient?
Quantity, not importance. Macronutrients are needed in amounts measured in grams, and they supply the energy the body runs on along with the raw material for tissue. Micronutrients are needed in amounts measured in milligrams or micrograms and supply almost no energy at all. They work instead as the parts enzymes need in order to function, as signals directing processes such as bone formation and nerve conduction, and as components of structures such as hemoglobin and thyroid hormone. A shortage of either causes trouble, but the two shortages look different. Too little energy or protein shows as weight loss and wasting, while too little of one micronutrient produces a specific pattern tied to whatever that nutrient does.
| Group | Examples | Main job |
|---|---|---|
| Carbohydrate | Starches, sugars, fiber | Ready energy, plus fiber that feeds gut bacteria |
| Protein | Amino acids from meat, dairy, legumes, grains | Building and repairing tissue, enzymes, antibodies |
| Fat | Oils, butter, nuts, oily fish | Concentrated energy, cell membranes, carrying fat soluble vitamins |
| Vitamins | Vitamin C, the B group, vitamins A, D, E and K | Enabling specific chemical reactions |
| Minerals | Calcium, iron, iodine, zinc, potassium | Bone, oxygen carriage, nerve and muscle signaling |
What makes a nutrient essential?
Essential means the body cannot make it, or cannot make enough of it, so it has to arrive in the diet. Nine of the amino acids in protein are essential in this sense, as are two fatty acids, most vitamins, and a list of minerals. Others are not: the body builds the remaining amino acids from what it has, and makes vitamin D in skin exposed to sunlight. Bacteria in the large intestine supply some vitamin K and several B vitamins. A few nutrients are called conditionally essential, meaning the body normally makes enough but cannot during illness, rapid growth or recovery from major injury.
How does the body get at them?
Almost nothing in food is absorbed in the form it arrives in. Digestion breaks starch into simple sugars, protein into amino acids and fat into fatty acids, each step driven by a specific enzyme, before anything crosses the intestinal wall. What is taken up depends on more than what was eaten. Iron from plant sources is absorbed less readily than iron from meat, calcium uptake depends on vitamin D, and the fat soluble vitamins need fat present in the same meal.
Used in a sentence
The dietitian reviewed the patient's intake of key nutrients as part of the nutrition assessment.
Good to know
An essential nutrient is one the body cannot manufacture in adequate amounts on its own, which is distinct from a nutrient the body can synthesize internally when dietary intake is limited.
Word origin
Where “nutrient” comes from
From Latin nutrire, meaning to nourish or feed.