Pistachio (Pistacia vera) nuts are an excellent source of fiber (especially insoluble fiber), potassium, and vitamin E (especially gamma-tocopherol, as described below). Pistachio nuts are also a very good source of catechins, lutein, manganese, thiamin, and vitamin B6, as well as monounsaturated fatty acids such as oleic acid.
Pistachio nuts are also a source of CoQ10, cyanidin-3-galactoside, folate, magnesium, myricetin, and resveratrol, most of which have been shown to have chemopreventive properties. However, pistachios also contain a substantial amount of copper.
In addition, pistachio nuts are a rich source of beta-sitosterol, which competes with the absorption of cholesterol from food, helping to lower cholesterol. Pistachios are neuroprotective and have high antioxidant activity. Consumption of pistachio nuts is also associated with lower levels of inflammatory markers. These qualities may account for an observed inverse relationship between pistachio nut consumption and cardiovascular and type 2 diabetes risk factors. Despite their high caloric and fat content, adding a moderate amount of nuts to the diet has been shown not to result in weight gain.

Breast cancer-related effects of eating pistachio nuts

Higher intake of tree nuts has been linked to lower breast cancer risk, and estrogen receptor negative (ER-) breast cancer in particular, although not all studies are in agreement. There is little specific evidence concerning pistachio nut consumption and breast cancer risk. One 2018 study reported that pistachio kernel extract reduced hormone receptor positive (ER+/PR+) breast cancer cell viability in a dose and time dependent manner.
High intake of dietary fiber and vitamin E (but not vitamin E supplements) have both been reported to be associated with reduced risk of breast cancer.

Gamma-tocopherol form of vitamin E

Vitamin E comprises a group of eight related vitamins, including four tocopherols (α, β, γ, and δ-tocopherol) and four tocotrienols (α, β, γ, and δ-tocotrienol). Alpha-tocopherol (α-tocopherol) is the most abundant form of vitamin E and is the isoform typically found in vitamin E supplements.
As noted above, pistachio nuts are an excellent source of gamma-tocopherol (γ-tocopherol), which has greater chemopreventive effects than other forms of vitamin E.
However, one study reported different effects for alpha-tocopherol and gamma-tocopherol in combination with docosahexaenoic acid (DHA) (found in fatty fish) in triple negative breast cancer cells. DHA alone was shown to induce apoptosis (programmed cell death), as expected. The addition of gamma-tocotrienol increased apoptotic events in the cells. However, alpha-tocopherol blocked DHA-induced apoptosis.

Copper

Pistachio nuts should be consumed in moderation since they contain some copper (approximately 0.37 mg per ounce). One 2024 study found that relatively high levels of copper in the urine of girls were associated with increased breast density two years after menarche. On the other hand, other studies have reported that copper does not appear to increase breast cancer risk significantly. However, it does appear to increase the risk of recurrence. Copper has been shown to promote angiogenesis and metastasis, especially in aggressive forms of breast cancer such as inflammatory (IBC), triple negative (ER-/PR-/HER2-), and HER2 overexpressing (HER2+) breast cancer.
While copper is a vital nutrient, women with breast cancer should not exceed the Recommended Daily Allowance (RDA) of approximately 0.9 mg.

Additional comments

Since most pistachio nuts are sold roasted and salted, those who are concerned about their intake of sodium should seek out pistachios with no added salt.

Pistachio nuts and aflatoxin

The U.S. is the world's second largest producer of pistachio nuts (most of which are grown in California), whereas Iran is the largest producer. Turkey, Syria, and China also produce significant volumes. Pistachio nuts typically are infected to some extent with molds that produce aflatoxins, which are mutagenic, carcinogenic and teratogenic and cause immuno-suppression in humans. Aflatoxin B1 has been shown to cause liver cancer, especially in hepatitis B-positive individuals. While U.S. pistachio nuts generally contain very low levels of aflatoxins, non-U.S. pistachios sometimes contain unacceptably high levels. Dangerous levels have been reported in pistachio nuts produced in Iran and Morocco.
Pistachio nuts normally are dried soon after harvest to minimize shell staining and decay and to ensure safety. Pistachio nuts sold without the shell are much more likely to have a high level of contamination than pistachios sold inshell.
To maximize safety, select inshell pistachio nuts that have not been dyed red (the dye itself is not healthy and is sometimes used to cover up stains). Avoid eating any pistachios with stained or missing shells, that have a sour taste, or any signs of mold, excessive moisture or insect damage.

Bottom line

Apart from their relatively high copper content, pistachio nuts have a beneficial anti-cancer profile, with a favorable mix of fat, fiber, vitamin E and phytochemicals. However, potential contamination with aflatoxin and additives used in processing or preserving the nuts are a real concern. Therefore, pistachio nuts are best enjoyed (in moderation) if purchased inshell and organically grown in the U.S., with minimal salt added if roasted.

Sources of information provided in this webpage

The information above, which is updated continually as new research becomes available, has been developed based solely on the results of academic studies. Clicking on any of the underlined terms will take you to its tag or webpage, which contain more extensive information.
Below are links to 20 recent studies concerning this food and its components. For a more complete list of studies, please click on pistachio nut.