Pistachios are eaten raw, toasted, salted, or sweetened as a snack. They have a sweet, fruity taste. Chopped or ground, they are often used in pastries, sweets, or for sprinkling over desserts.
From Wikipedia: “The pistachio (Pistacia vera), a member of the cashew family, is a small tree originating from Central Asia and the Middle East. The tree produces seeds that are widely consumed as food. Pistacia vera often is confused with other species in the genus Pistacia that are also known as pistachio. These other species can be distinguished by their geographic distributions (in the wild) and their seeds which are much smaller and have a soft shell.”
“The bush grows up to 10 m (33 ft) tall. It has deciduous pinnate leaves 10–20 centimeters (4–8 inches) long. The plants are dioecious, with separate male and female trees. The flowers are apetalous and unisexual, and borne in panicles. The fruit is a drupe, containing an elongated seed, which is the edible portion. The seed, commonly thought of as a nut, is a culinary nut, not a botanical nut. ... When the fruit ripens, the shell changes from green to an autumnal yellow/red, and abruptly splits part way open ... The splitting open is a trait that has been selected by humans. ...
Each pistachio tree averages around 50 kilograms (110 lb) of seeds, or around 50,000, every two years. The shell of the pistachio is naturally a beige color, but it is sometimes dyed red or green in commercial pistachios. Originally, dye was applied by importers to hide stains on the shells caused when the seeds were picked by hand. Most pistachios are now picked by machine and the shells remain unstained, making dyeing unnecessary except to meet ingrained consumer expectations.“
“Pistachios are a nutritionally dense food. In a 100 gram serving, pistachios provide 562 calories and are a rich source (20% or more of the Daily Value or DV) of protein, dietary fiber, several dietary minerals and the B vitamins, thiamin and especially vitamin B6 at 131% DV. Pistachios are a good source (10–19% DV) of calcium, riboflavin, vitamin B5, folate, vitamin E , and vitamin K ...
The fat profile of raw pistachios consists of saturated fats, monounsaturated fats and polyunsaturated fats.Saturated fatty acids include palmitic acid (10% of total) and stearic acid (2%). Oleic acid is the most common monounsaturated fatty acid (51% of total fat) and linoleic acid, a polyunsaturated fatty acid, is 31% of total fat. Relative to other tree nuts, pistachios have a lower amount of fat and calories but higher amounts of potassium, vitamin K, γ-tocopherol, and certain phytochemicals such as carotenoids and phytosterols.”
“Like other members of the Anacardiaceae family (which includes poison ivy, sumac, mango, and cashew), pistachios contain urushiol, an irritant that can cause allergic reactions.”
Research and health effects:
“In July 2003, the United States' Food and Drug Administration (FDA) approved the first qualified health claim specific to seeds lowering the risk of heart disease: "Scientific evidence suggests but does not prove that eating 1.5 ounces (42.5 g) per day of most nuts, such as pistachios, as part of a diet low in saturated fat and cholesterol may reduce the risk of heart disease". Although pistachios contain many calories, epidemiologic studies have provided strong evidence that their consumption is not associated with weight gain or obesity.
A 2015 systematic review and meta-analysis of randomized controlled trials concluded that pistachio consumption in persons without diabetes mellitus appears to modestly lower systolic and diastolic blood pressure. Several mechanisms for pistachios' antihypertensive properties have been proposed. These mechanisms include pistachios' high levels of the amino acid arginine (a precursor of the blood vessel dilating compound nitric oxide); high levels of phytosterols and monounsaturated fatty acids; and improvement of endothelial cell function through multiple mechanisms including reductions in circulating levels of oxidized low density lipoprotein cholesterol and pro-inflammatory chemical signals.”
Toxins and safety concerns:
“As with other tree seeds, aflatoxin is found in poorly harvested or processed pistachios. Aflatoxins are potent carcinogenic chemicals produced by molds such as Aspergillus flavus and Aspergillus parasiticus. The mold contamination may occur from soil, poor storage, and spread by pests. High levels of mold "growing" typically appear as gray to black filament-like "growing". It is unsafe to eat mold-infected and aflatoxin-contaminated pistachios. Aflatoxin contamination is a frequent risk, particularly in warmer and humid environments. Food contaminated with aflatoxins has been found as the cause of frequent outbreaks of acute illnesses in parts of the world. In some cases, such as Kenya, this has led to several deaths.
Pistachio shells typically split naturally prior to harvest, with a hull covering the intact seeds. The hull protects the kernel from invasion by molds and insects, but this hull protection can be damaged in the orchard by poor orchard management practices, by birds, or after harvest, which makes it much easier for pistachios to be exposed to contamination. Some pistachios undergo so-called "early split", wherein both the hull and the shell split. Damage or early splits can lead to aflatoxin contamination. In some cases, a harvest may be treated to keep contamination below strict food safety thresholds; in other cases, an entire batch of pistachios must be destroyed because of aflatoxin contamination. Pistachio shells may be helpful in cleaning up pollution created by mercury emissions.”