Pistachio nuts

The pistachio is a seed, and a culinary nut rather than a botanical one. It grows inside a fruit with a hard shell, on a tree in the cashew family. That family also holds the mango and poison ivy. When the fruit ripens, the shell splits partly open with a pop, a trait people have selected for.

Raw pistachios have 560 calories per 100 g, or 159 in an ounce (28 g), and 20.2 g of protein per 100 g. The protein is complete, scoring 100 out of 100 for essential amino acids. An ounce also gives 3 g of fiber and 28% of the Daily Value for vitamin B6.

Compared with other nuts, pistachios are high in lutein, the pigment of the retina. An ounce has 823 µg (micrograms) of lutein and zeaxanthin.

Pistachios may also hold slightly less usable energy than their label suggests. In a feeding study, the measured energy was 5% below the standard calculation. And the shell may help with portions. In two small university studies, people who ate in-shell pistachios, or who left the empty shells in sight, ate fewer calories.

Health benefits of pistachios

• ★★★Lower “bad” LDL cholesterolAcross 12 trials of pistachios alone, LDL fell by 3.8 mg/dL. Across 61 trials of tree nuts as a group, one daily ounce lowered it by 4.8 mg/dL.
• ★★Slightly lower blood sugar markers in prediabetesAbout 57 g of pistachios a day lowered fasting blood sugar and insulin resistance in 54 adults with prediabetes. In another trial, HbA1c (average blood sugar) fell 0.2 points, though pooled trials found no HbA1c change.
• ★★Slightly lower blood pressureThe top number fell by about 3 points (2.9 mm Hg systolic) across 17 trials. A pooled analysis of 13 trials found a drop of 2.1 mm Hg systolic, and no change in the bottom number.
• ★★No clear effect on weightAcross 11 trials, body weight and waist size did not change in a clear way. In a 4-month weight-loss program, people lost 4.9% of their weight with pistachios and 5.1% without.
• ★Fewer calories eaten from in-shell nutsIn 140 students, people ate about 125 calories of in-shell pistachios against 211 of shelled ones. In another study, shells left in sight cut daily intake by 48 calories (216 against 264).

Who should be careful with pistachios

Most people can eat pistachios freely. Take a little care if one of these applies:

• Tree nut allergy. Pistachio is a tree nut, and tree nuts are one of the major allergens that US labels must declare. It is closely linked to cashew allergy. In an Israeli group of 100 children with cashew allergy, 82 were also allergic to pistachio. Avoid it unless your allergist says otherwise.
• Salted pistachios. Raw pistachios have about 1 mg of sodium per 100 g. Dry roasted salted ones have 428 mg per 100 g in USDA data, about 120 mg in an ounce (28 g). That is roughly 5% of the 2,300 mg Daily Value, so choose unsalted if you limit sodium.
• Aflatoxin. Pistachios are among the foods most prone to the molds that make aflatoxins. These toxins are linked to liver cancer at high exposure. The EU allows 8 µg/kg of aflatoxin B1 and 10 µg/kg in total in pistachios sold to consumers. The FDA treats pistachios above 20 ppb (parts per billion) as adulterated. The EU also runs extra import checks on pistachios from some origins. Lots sold in regular stores must meet these limits, so the risk for most people is small.

How to choose, store and eat pistachios

• In the shell: in one study, people given in-shell pistachios ate 41% fewer calories than people given shelled ones. In another, leaving the empty shells in sight cut intake by 48 calories. Both studies were small.
• Raw or roasted: in a digestion model, raw and roasted salted pistachios released their polyphenols, lutein and vitamin E alike. Unsalted keeps sodium near 1 mg per 100 g.
• How much: the FDA claim and one weight-loss trial used 1.5 ounces (42 g) a day. The prediabetes trial used 57 g and the eye pigment trial 2 ounces. An ounce is 159 calories.

Keep pistachios in a clean, moisture-free, airtight container. In the refrigerator at 40°F (4°C) or lower, they keep for up to a year. In the freezer at 0°F (−18°C) or lower, they keep for three years, according to University of California extension.

History of pistachios

The word pistachio comes from an ancient Persian word, pistag. The tree is native to southern Central Asia, including northern Afghanistan and northeastern Iran. The earliest evidence of production comes from Bronze Age Central Asia, at Djarkutan in what is now Uzbekistan.

Pistachio was probably domesticated within that range about 3,000 years ago. A 2022 study argues it spread west by at least 2,000 years ago, and east only at the end of the first millennium AD. Its seeds stayed rare at archaeological sites outside its home range even into the mid-second millennium AD.

Greek writers such as Theophrastus and Dioscorides described the tree, and the Romans brought it from Asia to Europe in the first century AD. It reached California as a garden tree in 1854. The USDA’s David Fairchild brought in hardier types from China in 1904 and 1905.

The crop was promoted commercially from 1929, and the first commercial harvest in California came in 1976.

Today the United States, Turkey and Iran produce about 87% of the world crop. In 2024 world production was about 1.38 million tonnes. The United States grew about 499,000 tonnes, Turkey 383,000 and Iran 316,000.

Pistachio shells are naturally beige. They were once dyed red to hide stains left by hand picking, but most nuts are now harvested by machine and left undyed. Large piles of moist pistachios can heat themselves because of their oil. They can catch fire if stored with combustible fabric such as jute.