The peanut, also known as the groundnut and the goober and taxonomically classified as Arachis hypogaea, is a legume crop grown mainly for its edible seeds. It is widely grown in the tropics and subtropics, being important to both small and large commercial producers. It is classified as both a grain legume and, because of its high oil content, an oil crop. World annual production of shelled peanuts was 42 million tonnes in 2014. Atypically among crop plants, peanut pods develop underground rather than aboveground. It is this characteristic that the botanist Linnaeus used to assign the specific name hypogaea, which means "under the earth."
As a legume, the peanut belongs to the botanical family Fabaceae; this is also known as Leguminosae, and commonly known as the bean, or pea, family. Like most other legumes, peanuts harbor symbiotic nitrogen-fixing bacteria in root nodules. This capacity to fix nitrogen means peanuts require less nitrogen-containing fertilizer and improve soil fertility, making them valuable in crop rotations.
Peanuts are similar in taste and nutritional profile to tree nuts such as walnuts and almonds, and are often served in similar ways in Western cuisines. The botanical definition of a "nut" is a fruit whose ovary wall becomes very hard at maturity. Using this criterion, the peanut is not a true nut, but rather a legume. However, for culinary purposes and in common English language usage, peanuts are usually referred to as nuts.
Peanuts are rich in energy (567 calories per 100 g) and contain health benefiting nutrients, minerals, antioxidants and vitamins that are essential for optimum health.
They compose sufficient levels of mono-unsaturated fatty acids (MUFA), especially oleic acid. MUFA helps lower LDL or "bad cholesterol" and increase HDL or "good cholesterol” level in the blood. Research studies suggest that Mediterranean diet which is rich in monounsaturated fatty acids help to prevent coronary artery disease and stroke risk by favoring healthy blood lipid profile.
Peanut kernels are good source of dietary protein; compose fine quality amino acids that are essential for growth and development.
Research studies have shown that peanuts contain high concentrations of poly-phenolic antioxidants, primarily p-coumaric acid. This compound has been thought to reduce the risk of stomach cancer by limiting formation of carcinogenic nitrosamines in the stomach.
Peanuts are an excellent source of resveratrol, another polyphenolic antioxidant. Resveratrol has been found to have protective function against cancers, heart disease, degenerative nerve disease, Alzheimer's disease, and viral/fungal infections.
Furthermore, studies suggest that resveratrol may reduce stroke risk through altering molecular mechanisms in the blood vessels (reducing susceptibility to vascular damage through decreased activity of angiotensin, a systemic hormone responsible for blood vessel constriction that would elevate blood pressure), and by increasing production of vasodilator hormone, nitric oxide.
Recent research studies suggest that roasting/boiling enhances antioxidant bio-availability in the peanuts. It has been found that boiled peanuts have two and four-fold increase in isoflavone antioxidants biochanin-A and genistein content, respectively.
The kernels are an excellent source of vitamin E (a-tocopherol); containing about 8 g per100 g. vitamin E is a powerful lipid soluble antioxidant which helps maintain the integrity of cell membrane of mucus membranes and skin by protecting from harmful oxygen free radicals.
The nuts are packed with many important B-complex groups of vitamins such as riboflavin, niacin, thiamin, pantothenic acid, vitamin B-6, and folates. 100 g of peanuts provide about 85% of RDI of niacin, which contribute to brain health and blood flow to brain.
The nuts are rich source of minerals like copper, manganese, potassium, calcium, iron, magnesium, zinc, and selenium.
Just a handful of peanuts per day provides enough recommended levels of phenolic anti-oxidants, minerals, vitamins, and protein.