Nut (fruit)

Nut (fruit)

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A nut is a hard-shelled fruit
Fruit
In broad terms, a fruit is a structure of a plant that contains its seeds.The term has different meanings dependent on context. In non-technical usage, such as food preparation, fruit normally means the fleshy seed-associated structures of certain plants that are sweet and edible in the raw state,...

 of some plant
Plant
Plants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...

s having an indehiscent seed. While a wide variety of dried seeds and fruits are called nuts in English, only a certain number of them are considered by biologists to be true nuts. Nuts are an important source of nutrients for both humans and wildlife.

Nuts are a composite of the seed and the fruit, where the fruit does not open to release the seed. Most seeds come from fruits, and the seeds are free of the fruit, unlike nuts such as hazelnut
Hazelnut
A hazelnut is the nut of the hazel and is also known as a cob nut or filbert nut according to species. A cob is roughly spherical to oval, about 15–25 mm long and 10–15 mm in diameter, with an outer fibrous husk surrounding a smooth shell. A filbert is more elongated, being about twice...

s, hickories, chestnut
Chestnut
Chestnut , some species called chinkapin or chinquapin, is a genus of eight or nine species of deciduous trees and shrubs in the beech family Fagaceae, native to temperate regions of the Northern Hemisphere. The name also refers to the edible nuts they produce.-Species:The chestnut belongs to the...

s and acorn
Acorn
The acorn, or oak nut, is the nut of the oaks and their close relatives . It usually contains a single seed , enclosed in a tough, leathery shell, and borne in a cup-shaped cupule. Acorns vary from 1–6 cm long and 0.8–4 cm broad...

s, which have a stony fruit wall and originate from a compound ovary. Culinary usage of the term is less restrictive, and some nuts as defined in food preparation, like pistachio
Pistachio
The pistachio, Pistacia vera in the Anacardiaceae family, is a small tree originally from Persia , which now can also be found in regions of Syria, Lebanon, Turkey, Greece, Kyrgyzstan, Turkmenistan, India, Pakistan, Egypt, Sicily and possibly Afghanistan , as well as in the United States,...

s and Brazil nut
Brazil Nut
The Brazil nut is a South American tree in the family Lecythidaceae, and also the name of the tree's commercially harvested edible seed.- Order :...

s, are not nuts in a biological sense. Everyday common usage of the term often refers to any hard-walled, edible kernel as a nut.

Botanical definition


A nut in botany
Botany
Botany, plant science, or plant biology is a branch of biology that involves the scientific study of plant life. Traditionally, botany also included the study of fungi, algae and viruses...

 is a simple dry fruit
Fruit
In broad terms, a fruit is a structure of a plant that contains its seeds.The term has different meanings dependent on context. In non-technical usage, such as food preparation, fruit normally means the fleshy seed-associated structures of certain plants that are sweet and edible in the raw state,...

 with one seed
Seed
A seed is a small embryonic plant enclosed in a covering called the seed coat, usually with some stored food. It is the product of the ripened ovule of gymnosperm and angiosperm plants which occurs after fertilization and some growth within the mother plant...

 (rarely two) in which the ovary
Ovary (plants)
In the flowering plants, an ovary is a part of the female reproductive organ of the flower or gynoecium. Specifically, it is the part of the pistil which holds the ovule and is located above or below or at the point of connection with the base of the petals and sepals...

 wall becomes very hard (stony or woody) at maturity, and where the seed remains attached or fused with the ovary wall. Most nuts come from the pistils with inferior ovaries (see flower
Flower
A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants . The biological function of a flower is to effect reproduction, usually by providing a mechanism for the union of sperm with eggs...

) and all are indehiscent (not opening at maturity). True nuts are produced, for example, by some plant families of the order
Order (biology)
In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...

 Fagales
Fagales
The Fagales are an order of flowering plants, including some of the best known trees. The order name is derived from genus Fagus, Beeches. They belong among the rosid group of dicotyledons...

.

Order Fagales
  • Family Fagaceae
    Fagaceae
    The family Fagaceae, or beech family, comprises about 900 species of both evergreen and deciduous trees and shrubs, which are characterized by alternate simple leaves with pinnate venation, unisexual flowers in the form of catkins, and fruit in the form of cup-like nuts. Fagaceous leaves are often...

    • Beech
      Beech
      Beech is a genus of ten species of deciduous trees in the family Fagaceae, native to temperate Europe, Asia and North America.-Habit:...

       (Fagus)
    • Chestnut
      Chestnut
      Chestnut , some species called chinkapin or chinquapin, is a genus of eight or nine species of deciduous trees and shrubs in the beech family Fagaceae, native to temperate regions of the Northern Hemisphere. The name also refers to the edible nuts they produce.-Species:The chestnut belongs to the...

       (Castanea)
    • Oak
      Oak
      An oak is a tree or shrub in the genus Quercus , of which about 600 species exist. "Oak" may also appear in the names of species in related genera, notably Lithocarpus...

       (Quercus)
    • Stone-oak
      Lithocarpus
      Lithocarpus is a genus in the beech family Fagaceae, differing from Quercus in the erect male spikes. The World Checklist accepts 334 species, though some other texts suggest as few as 100 species. About 100 Asian species of the genus were formerly treated in the genus Pasania. All but one are...

      , Tanoak
      Tanoak
      Tanoak, formerly known taxonomically as Lithocarpus densiflorus, was recently moved into a new genus, Notholithocarpus, based on multiple lines of evidence....

       (Lithocarpus)
  • Family Betulaceae
    Betulaceae
    Betulaceae, or the Birch Family, includes six genera of deciduous nut-bearing trees and shrubs, including the birches, alders, hazels, hornbeams and hop-hornbeams, numbering about 130 species...

    • Alder
      Alder
      Alder is the common name of a genus of flowering plants belonging to the birch family . The genus comprises about 30 species of monoecious trees and shrubs, few reaching large size, distributed throughout the North Temperate Zone and in the Americas along the Andes southwards to...

       (Alnus)
    • Hazel
      Hazel
      The hazels are a genus of deciduous trees and large shrubs native to the temperate northern hemisphere. The genus is usually placed in the birch family Betulaceae, though some botanists split the hazels into a separate family Corylaceae.They have simple, rounded leaves with double-serrate margins...

      , Filbert (Corylus)
    • Hornbeam
      Hornbeam
      Hornbeams are relatively small hardwood trees in the genus Carpinus . Though some botanists grouped them with the hazels and hop-hornbeams in a segregate family, Corylaceae, modern botanists place the hornbeams in the birch subfamily Coryloideae...


Culinary definition and uses


A nut in cuisine
Cuisine
Cuisine is a characteristic style of cooking practices and traditions, often associated with a specific culture. Cuisines are often named after the geographic areas or regions that they originate from...

 is a much less restrictive category than a nut in botany, as the term is applied to many seed
Seed
A seed is a small embryonic plant enclosed in a covering called the seed coat, usually with some stored food. It is the product of the ripened ovule of gymnosperm and angiosperm plants which occurs after fertilization and some growth within the mother plant...

s that are not botanically true nuts. Any large, oily kernel found within a shell and used in food may be regarded as a nut.

Because nuts generally have a high oil content, they are a highly prized food and energy source. A large number of seeds are edible by humans and used in cooking, eaten raw, sprouted, or roasted as a snack food
Snack food
A snack is a portion of food oftentimes smaller than that of a regular meal, that is generally eaten between meals. Snacks come in a variety of forms including packaged and processed foods and items made from fresh ingredients at home....

, or pressed for oil that is used in cookery and cosmetics
Cosmetics
Cosmetics are substances used to enhance the appearance or odor of the human body. Cosmetics include skin-care creams, lotions, powders, perfumes, lipsticks, fingernail and toe nail polish, eye and facial makeup, towelettes, permanent waves, colored contact lenses, hair colors, hair sprays and...

. Nuts (or seeds generally) are also a significant source of nutrition for wildlife. This is particularly true in temperate climates where animals such as jay
Jay
The jays are several species of medium-sized, usually colorful and noisy, passerine birds in the crow family Corvidae. The names jay and magpie are somewhat interchangeable, and the evolutionary relationships are rather complex...

s and squirrel
Squirrel
Squirrels belong to a large family of small or medium-sized rodents called the Sciuridae. The family includes tree squirrels, ground squirrels, chipmunks, marmots , flying squirrels, and prairie dogs. Squirrels are indigenous to the Americas, Eurasia, and Africa and have been introduced to Australia...

s store acorn
Acorn
The acorn, or oak nut, is the nut of the oaks and their close relatives . It usually contains a single seed , enclosed in a tough, leathery shell, and borne in a cup-shaped cupule. Acorns vary from 1–6 cm long and 0.8–4 cm broad...

s and other nuts during the autumn to keep them from starving during the late autumn, all of winter, and early spring.

Nuts used for food, whether true nut or not, are among the most common food allergens
Food allergy
A food allergy is an adverse immune response to a food protein. They are distinct from other adverse responses to food, such as food intolerance, pharmacological reactions, and toxin-mediated reactions....

.

Some fruits and seeds that do not meet the botanical definition but are nuts in the culinary sense:
  • Almond
    Almond
    The almond , is a species of tree native to the Middle East and South Asia. Almond is also the name of the edible and widely cultivated seed of this tree...

    s, pecan
    Pecan
    The pecan , Carya illinoinensis, is a species of hickory, native to south-central North America, in Mexico from Coahuila south to Jalisco and Veracruz, in the United States from southern Iowa, Illinois, Missouri, and Indiana east to western Kentucky, southwestern Ohio, North Carolina, South...

    s and walnut
    Walnut
    Juglans is a plant genus of the family Juglandaceae, the seeds of which are known as walnuts. They are deciduous trees, 10–40 meters tall , with pinnate leaves 200–900 millimetres long , with 5–25 leaflets; the shoots have chambered pith, a character shared with the wingnuts , but not the hickories...

    s are the edible seeds of drupe
    Drupe
    In botany, a drupe is a fruit in which an outer fleshy part surrounds a shell of hardened endocarp with a seed inside. These fruits develop from a single carpel, and mostly from flowers with superior ovaries...

     fruits — the leathery "flesh" is removed at harvest.
  • Brazil nut
    Brazil Nut
    The Brazil nut is a South American tree in the family Lecythidaceae, and also the name of the tree's commercially harvested edible seed.- Order :...

     is the seed from a capsule
    Capsule (fruit)
    In botany a capsule is a type of simple, dry fruit produced by many species of flowering plants. A capsule is a structure composed of two or more carpels that in most cases is dehiscent, i.e. at maturity, it splits apart to release the seeds within. A few capsules are indehiscent, for example...

    .
  • Candlenut
    Candlenut
    Aleurites moluccana, the Candlenut, is a flowering tree in the spurge family, Euphorbiaceae, also known as Candleberry, Indian walnut, Kemiri, Varnish tree, Nuez de la India, Buah keras or Kukui nut tree....

     (used for oil) is a seed.
  • Cashew
    Cashew
    The cashew is a tree in the family Anacardiaceae. Its English name derives from the Portuguese name for the fruit of the cashew tree, caju, which in turn derives from the indigenous Tupi name, acajú. It is now widely grown in tropical climates for its cashew nuts and cashew apples.-Etymology:The...

     nut is a seed.
  • Chilean hazelnut or Gevuina
  • Horse-chestnut
    Aesculus
    The genus Aesculus comprises 13-19 species of woody trees and shrubs native to the temperate northern hemisphere, with 6 species native to North America and 7-13 species native to Eurasia; there are also several hybrids. Species are deciduous or evergreen...

     is an inedible capsule
    Capsule (fruit)
    In botany a capsule is a type of simple, dry fruit produced by many species of flowering plants. A capsule is a structure composed of two or more carpels that in most cases is dehiscent, i.e. at maturity, it splits apart to release the seeds within. A few capsules are indehiscent, for example...

    .
  • Macadamia
    Macadamia
    Macadamia is a genus of nine species of flowering plants in the family Proteaceae, with a disjunct distribution native to eastern Australia , New Caledonia and Sulawesi in Indonesia ....

     nut is a creamy white kernel (Macadamia integrifolia
    Macadamia integrifolia
    Macadamia integrifolia is a tree in the Proteaceae family, native to Queensland in Australia. Common names include Macadamia Nut, Bauple Nut, Queensland Nut or Nut Oak....

    ).
  • Malabar chestnut
    Pachira aquatica
    Pachira aquatica is a tropical wetland tree of the genus Pachira, native to Central and South America where it grows in swamps. It is known by the common names Malabar chestnut, Guiana chestnut, provision tree, saba nut, Monguba , Pumpo and is commercially sold under the name money tree and money...

  • Corn nut
    Corn nut
    Corn nuts, also known as toasted corn or corn bits, is a snack food made of roasted or deep-fried corn kernels.- Preparation :Corn nuts are prepared by soaking whole corn kernels in water for three days, then deep-frying them in oil until they are hard and brittle.The kernels are soaked because...

     is a cooked kernel
  • Mongongo
    Mongongo
    Formerly known as Ricinodendron rautanenii, the mongongo tree is a member of the family Euphorbiaceae and of the monotypic genus Schinziophyton. A large, spreading tree, the mongongo reaches 15-20 metres tall. It is found on wooded hills and amongst sand dunes, and is associated with the...

  • Peanut
    Peanut
    The peanut, or groundnut , is a species in the legume or "bean" family , so it is not a nut. The peanut was probably first cultivated in the valleys of Peru. It is an annual herbaceous plant growing tall...

     is a legume.
  • Pine nut
    Pine nut
    Pine nuts are the edible seeds of pines . About 20 species of pine produce seeds large enough to be worth harvesting; in other pines the seeds are also edible, but are too small to be of great value as a human food....

     is the seed of several species of pine
    Pine
    Pines are trees in the genus Pinus ,in the family Pinaceae. They make up the monotypic subfamily Pinoideae. There are about 115 species of pine, although different authorities accept between 105 and 125 species.-Etymology:...

     (coniferous
    Pinophyta
    The conifers, division Pinophyta, also known as division Coniferophyta or Coniferae, are one of 13 or 14 division level taxa within the Kingdom Plantae. Pinophytes are gymnosperms. They are cone-bearing seed plants with vascular tissue; all extant conifers are woody plants, the great majority being...

     trees).
  • Pistachio
    Pistachio
    The pistachio, Pistacia vera in the Anacardiaceae family, is a small tree originally from Persia , which now can also be found in regions of Syria, Lebanon, Turkey, Greece, Kyrgyzstan, Turkmenistan, India, Pakistan, Egypt, Sicily and possibly Afghanistan , as well as in the United States,...

     nut is the seed of a thin-shelled drupe.

Nutritional benefits



Several epidemiological studies have revealed that people who consume nuts regularly are less likely to suffer from coronary heart disease
Coronary heart disease
Coronary artery disease is the end result of the accumulation of atheromatous plaques within the walls of the coronary arteries that supply the myocardium with oxygen and nutrients. It is sometimes also called coronary heart disease...

 (CHD). Nuts were first linked to protection against CHD in 1993. Since then many clinical trial
Clinical trial
Clinical trials are a set of procedures in medical research and drug development that are conducted to allow safety and efficacy data to be collected for health interventions...

s have found that consumption of various nuts such as almond
Almond
The almond , is a species of tree native to the Middle East and South Asia. Almond is also the name of the edible and widely cultivated seed of this tree...

s and walnut
Walnut
Juglans is a plant genus of the family Juglandaceae, the seeds of which are known as walnuts. They are deciduous trees, 10–40 meters tall , with pinnate leaves 200–900 millimetres long , with 5–25 leaflets; the shoots have chambered pith, a character shared with the wingnuts , but not the hickories...

s can lower serum LDL cholesterol concentrations. Although nuts contain various substances thought to possess cardioprotective effects, scientists believe that their Omega 3 fatty acid
Fatty acid
In chemistry, especially biochemistry, a fatty acid is a carboxylic acid with a long unbranched aliphatic tail , which is either saturated or unsaturated. Most naturally occurring fatty acids have a chain of an even number of carbon atoms, from 4 to 28. Fatty acids are usually derived from...

 profile is at least in part responsible for the hypolipidemic response observed in clinical trials.

In addition to possessing cardioprotective effects, nuts generally have a very low glycemic index
Glycemic index
The glycemic index, glycaemic index, or GI is a measure of the effects of carbohydrates on blood sugar levels. Carbohydrates that break down quickly during digestion and release glucose rapidly into the bloodstream have a high GI; carbohydrates that break down more slowly, releasing glucose more...

 (GI).
Consequently, dietitians frequently recommend nuts be included in diets prescribed for patients with insulin resistance
Insulin resistance
Insulin resistance is a physiological condition where the natural hormone insulin becomes less effective at lowering blood sugars. The resulting increase in blood glucose may raise levels outside the normal range and cause adverse health effects, depending on dietary conditions. Certain cell types...

 problems such as diabetes mellitus type 2
Diabetes mellitus type 2
Diabetes mellitus type 2formerly non-insulin-dependent diabetes mellitus or adult-onset diabetesis a metabolic disorder that is characterized by high blood glucose in the context of insulin resistance and relative insulin deficiency. Diabetes is often initially managed by increasing exercise and...

.

One study found that people who eat nuts live two to three years longer than those who do not. However, this may be because people who eat nuts tend to eat less junk food
Junk food
Junk food is an informal term applied to some foods that are perceived to have little or no nutritional value ; to products with nutritional value, but which also have ingredients considered unhealthy when regularly eaten; or to those considered unhealthy to consume at all...

.

Nuts contain the essential fatty acids linoleic and linolenic acids, and the fats in nuts for the most part are unsaturated fats, including monounsaturated fats.

Many nuts are good sources of vitamins E and B2, and are rich in protein, folate, fiber, and essential minerals such as magnesium, phosphorus, potassium, copper, and selenium.

Nuts are most healthy in their raw form. The reason is that up to 15% of the healthy oils that naturally occur in nuts are lost during the roasting process. Roasting at high temperatures could also cause chemicals that advance the aging process to form.

Raw or unroasted walnuts were found to have twice as many antioxidants as other nuts. Although initial studies suggested that antioxidants might promote health, later large clinical trials did not detect any benefit and suggested instead that excess supplementation is harmful.

Other uses


The nut of the horse-chestnut tree (Aesculus species, especially Aesculus hippocastanum), is called a conker in the British Isles
British Isles
The British Isles are a group of islands off the northwest coast of continental Europe that include the islands of Great Britain and Ireland and over six thousand smaller isles. There are two sovereign states located on the islands: the United Kingdom of Great Britain and Northern Ireland and...

. Conkers are inedible because they contain toxic glucoside
Glucoside
A glucoside is a glycoside that is derived from glucose. Glucosides are common in plants, but rare in animals. Glucose is produced when a glucoside is hydrolysed by purely chemical means, or decomposed by fermentation or enzymes....

 aesculin
Aesculin
Aesculin, also rendered Æsculin or Esculin, is a glucoside that naturally occurs in the horse chestnut , California Buckeye and in daphnin ....

. They are used in a popular children's game, known as conkers, where the nuts are threaded onto a strong cord and then each contestant attempts to break their opponent's conker by hitting it with their own. Horse chestnuts are also popular slingshot
Slingshot
A slingshot, shanghai, flip, bean shooter or catapult is a small hand-powered projectile weapon. The classic form consists of a Y-shaped frame held in the off hand, with two rubber strips attached to the uprights. The other ends of the strips lead back to a pocket which holds the projectile...

 ammunition.

Historical usage


Nuts were a major part of the human diet 780,000 years ago including the wild almond
Almond
The almond , is a species of tree native to the Middle East and South Asia. Almond is also the name of the edible and widely cultivated seed of this tree...

, prickly water lily
Euryale ferox
Euryale ferox is the only species in the genus Euryale. It is a flowering plant classified in the water lily family, Nymphaeaceae, although it is occasionally regarded as a distinct family Euryalaceae...

, acorns, pistachio
Pistachio
The pistachio, Pistacia vera in the Anacardiaceae family, is a small tree originally from Persia , which now can also be found in regions of Syria, Lebanon, Turkey, Greece, Kyrgyzstan, Turkmenistan, India, Pakistan, Egypt, Sicily and possibly Afghanistan , as well as in the United States,...

 and water chestnut
Water chestnut
Water chestnut may refer to either of two plants :* The Chinese water chestnut , eaten for its crisp corm* The Water caltrop , eaten for its starchy seed...

. Prehistoric humans developed an assortment of tools to crack open nuts during the pleistocene
Pleistocene
The Pleistocene is the epoch from 2,588,000 to 11,700 years BP that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....

 period. Aesculus californica
Aesculus californica
Aesculus californica is a species of buckeye that is native [ |] to California and southwest Oregon [Jackson, County], and the only buckeye native to these states.-Description:...

, was eaten by the Native Americans
Native Americans in the United States
Native Americans in the United States are the indigenous peoples in North America within the boundaries of the present-day continental United States, parts of Alaska, and the island state of Hawaii. They are composed of numerous, distinct tribes, states, and ethnic groups, many of which survive as...

 of California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...

 during famines after the toxic constituents were leached out.

Further reading


Books
  • Alasalvar, C. / Shahidi, F. (eds. 2008). Tree Nuts: Composition, Phytochemicals, and Health Effects. CRC Press. ISBN 9780849337352
  • Goldstein, M.C. / Goldstein, M.D. (2010). Healthy Foods: Fact versus Fiction. Greenwood. ISBN 9780313380969
  • John Harvey Kellogg
    John Harvey Kellogg
    John Harvey Kellogg was an American medical doctor in Battle Creek, Michigan, who ran a sanitarium using holistic methods, with a particular focus on nutrition, enemas and exercise. Kellogg was an advocate of vegetarianism and is best known for the invention of the corn flakes breakfast cereal...

    , “Nuts a coming food staple” (pp. 165-203), in: The Itinerary of a Breakfast (1920). New York and London. Funk & Wagnalls Company.
  • Preedy, V.R./Watson, R.R./Patel, V.B. (eds. 2011). Nuts and Seeds in Health and Disease Prevention. Academic Press. ISBN 9780123756886


Review articles on possible health benefits

External links