Nuts, including pistachios, are healthy when eaten in moderation. They contain a number of essential nutrients, including protein, fiber, thiamine, vitamin B-6, phosphorus, copper and manganese. There aren't a lot of risks associated with eating pistachios unless you eat them in large amounts or you're allergic, but there is a small risk these nuts could be contaminated with salmonella if they weren't properly handled by the company that roasted and packaged them.
A 1-ounce serving of pistachios, or about 49 nuts, contains more than 12 grams of fat, or 19 percent of the daily value. High fat intake is sometimes associated with an increased risk for heart disease. This is mainly the case with high intake of saturated fat, however, and only about 1.5 grams of the fat in a serving of pistachios comes from saturated fat. The rest comes from the heart-healthy unsaturated fats.
Despite their high fat content, pistachios in moderation may be beneficial for heart health. A study published in The American Journal of Clinical Nutrition in September 2008 found that including two servings of pistachios per day as part of a lower-fat diet may help decrease total cholesterol and low-density lipoprotein, or "bad" cholesterol.
Pistachios are also relatively high in calories, with each serving providing about 160 calories. Eating too many calories overall leads to weight gain. Snacking on a moderate amount of pistachio nuts isn't likely to cause this problem, however. A study published in Nutrition Journal in 2012 found that eating up to 2.5 ounces of pistachios per day for 12 weeks didn't cause weight gain.
Most Americans consume too much sodium, which can increase the risk for high blood pressure. If you choose salted pistachios, each serving has about 120 milligrams of sodium, or 5 percent of the daily value.
Choose unsalted pistachios instead, and they may actually help improve your blood pressure levels. A study published in Hypertension in 2012 found that eating a serving of pistachios per day may help lower blood pressure levels. Increasing this to two servings per day still had a benefit, but the decrease in blood pressure levels was smaller.
Risk of Contamination
Roasted nuts, including pistachios, can become contaminated with salmonella, which causes cramps, fever and diarrhea. Some people who get this foodborne illness need hospitalization, although most recover on their own within about a week. It used to be thought that the dry roasting process eliminated the need to worry about potential salmonella contamination in nuts, but now it is clear that dry roasting doesn't kill all salmonella on nuts.
There have been a few recalls of pistachios due to salmonella contamination, including one in 2013 that caused at least eight people from six different states to become ill. In this case, the manufacturer didn't follow proper cleanliness and safety precautions, and the U.S. Food and Drug Administration believes this is most likely the reason for the outbreak.
Potential for Allergic Reactions
If you're allergic to pistachios or other tree nuts, eating them could cause an allergic reaction with symptoms including shortness of breath, nausea, abdominal pain, vomiting, congestion, difficulty swallowing, diarrhea, itching of the mouth or throat, a rash or anaphylaxis. Tree nut allergies are one of the most common types of allergies, so foods containing tree nuts must include a statement saying so on the label. If you experience an allergic reaction after eating pistachios, seek emergency medical care.