Essential nutrient

An essential nutrient is a nutrient required for normal human body function that either cannot be synthesized by the body at all, or cannot be synthesized in amounts adequate for good health (e.g. niacin, choline), and thus must be obtained from a dietary source. Essential nutrients are also defined by the collective physiological evidence for their importance in the diet, as represented in e.g. US government approved tables for Dietary Reference Intake.

Some categories of essential nutrients include vitamins, dietary minerals, essential fatty acids, and essential amino acids. Different species have very different essential nutrients. For example, most mammals synthesize their own ascorbic acid, and it is therefore not considered an essential nutrient for such species. It is, however, an essential nutrient for human beings, who require external sources of ascorbic acid (known as Vitamin C in the context of nutrition).

Many essential nutrients are toxic in large doses (see hypervitaminosis or the nutrient pages themselves below). Some can be taken in amounts larger than required in a typical diet, with no apparent ill effects.

For humans

Fatty acids

Essential fatty acids cannot be synthesized by humans, as humans lack the desaturase enzymes required for their production.

• α-Linolenic acid (ALA, 18:3), an omega-3 fatty acid
• Linoleic acid (LA, 18:2), an omega-6 fatty acid

α-Linolenic acid is not used by the body in its original form. It is converted by the body into the required long-chain polyunsaturated fatty acids eicosapentaenoic acid (EPA, 20:5) and docosahexaenoic acid (DHA, 22:6). EPA and DHA can also be consumed from a direct source by consuming fish, fish oil or algal oil (vegetarian source).

Linoleic acid is not used by the body in its original form either. It is converted by the body into the required long-chain polyunsaturated fatty acids gamma-linolenic acid (GLA, 18:3), dihomo-gamma-linolenic acid (DGLA, 20:3) and arachidonic acid (AA, 20:4).

Amino acids

• Isoleucine
• Lysine
• Leucine
• Methionine
• Cystine
• Phenylalanine
• Threonine
• Tryptophan
• Valine
• Histidine
• Arginine

Carbohydrates

Carbohydrates are sugar molecules and chains of sugar molecules. Although no individual carbohydrate by itself is an essential nutrient in humans, mixed complex carbohydrates are essential for growth and development, especially during the infant years. As a general dietary recommendation, an expert scientific panel of the European Food Safety Authority reported that carbohydrates should supply 45â€"60% of daily energy as the reference intake.

Glucose can be supplied 1) by carbohydrate digestion, 2) by synthesis from amino acids and glycerol obtained from fat metabolism or 3) by de novo synthesis (called gluconeogenesis) which, without a concurrent carbohydrate supply, depletes nitrogen stores and is insufficient to maintain normal brain metabolism alone. However, the body can adapt to this state by producing ketones (a state called ketosis) to fuel the brain, which can only use glucose and ketones for fuel, unless carbohydrate stores are repleted.

For humans, glucose is the key source of energy via aerobic respiration, providing about 3.75 kilocalories (16 kilojoules) of food energy per gram.

Vitamins

• Vitamin A (beta-carotene, retinol)
• Vitamin B₁ (thiamin)
• Vitamin B₂ (riboflavin, vitamin G)
• Vitamin B₃ (niacin, vitamin P, vitamin PP)
• Vitamin B₅ (pantothenic acid)
• Vitamin B₆ (pyridoxine, pyridoxamine, or pyridoxal)
• Vitamin B₇ (biotin, vitamin H)
• Vitamin B₉ (folic acid, folate, vitamin M)
• Vitamin B₁₂ (cobalamin)
• Vitamin C (ascorbic acid)
• Vitamin D (ergocalciferol D₂, or cholecalciferol D₃)
• Vitamin E (tocopherol)
• Vitamin K (naphthoquinoids)

Dietary minerals

• Calcium (Ca)
• Chloride (Cl^âˆ')
• Chromium (Cr)
• Cobalt (Co) (as part of Vitamin B₁₂)
• Copper (Cu)
• Iodine (I)
• Iron (Fe)
• Magnesium (Mg)
• Manganese (Mn)
• Molybdenum (Mo)
• Phosphorus (P)
• Potassium (K)
• Selenium (Se)
• Sodium (Na)
• Zinc (Zn)

Other

• Choline

For plants

See also

• Nutrient
• List of macronutrients
• List of micronutrients
• Underweight
• Auxotrophy
• Avitaminosis (vitamin deficiency)
• Dietary Reference Intake
• Dietary supplement
• Food composition
• Illnesses related to poor nutrition
• Malnutrition
• Vitamin poisoning

References

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