Ever wondered why pistachios are green? If pistachios are fattening? If they're gluten free? In honor of Pistachio Day, we answer all your most pressing pistachio questions.

By Liz Steelman
February 26, 2018

It’s Pistachio Day (February 26), and although you love their distinctly nutty flavor and oddly satisfying task of cracking its shell, you probably don’t know all the wonderful and interesting mysteries pistachios hold in their shell. In celebration of the green drupe behind and many people’s ice cream flavor of choice, we answer three big questions you might have about the pistachio.

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Why are pistachios green?

Ever wondered why the inside of a pistachio is more similar to an avocado than almond? According to the American Pistachio Growers, you can credit a little thing called carotenoids as to why pistachios are green inside. If you’re thinking that word looks like “beta-carotene,” the fat-soluble pigment that gives carrots their zippy orange colors, you’re on the right track. Like beta-carotene, lutein and zeaxanthin are carotenoids—naturally occurring plant pigments that act as antioxidants. Combined with chlorophyll, these cartenoids provide the nut their yellow and green hues. Additionally the red and purples on the outside of pistachios come from the presence of the anxioxidants resveratrol and anthocyanins.

Are pistachios fattening?

The short answer: Not really! Though they do contain 45 grams of fat in a 100-gram serving, nearly 90 percent of the fat is mono- and polyunsaturated fats. “I think many people are still on the fat phobic train in which they associate any type of dietary fact with a fear of ‘getting fat,’" Liz Shaw, a registered dietitian who consults Wonderful Pistachios, told RealSimple.com in an e-mail. “I’m constantly helping clients move past the total fat numbers and instead focus on fueling their bodies with unsaturated, heart-healthy fats.” Pistachios are actually known as “the skinny nut,” since they have the lowest amount of calories per single ounce serving of any tree nut. You can eat 49 nuts as a healthy snack—the standard serving size—and at three calories a nut, still only consume 147 calories.

Are pistachios gluten free?

Yes, since pistachios are nuts and are not a cereal grain, they do not contain gluten. However, if one is allergic or sensitive to gluten, it’s recommended to check the packaging since some pistachios might be mixed with seasonings or other ingredients that do contain gluten.