Based on this meta-analysis, eating pistachios may lead to improvements in metabolic health and reduce risk factors for cardiovascular disease.

Researchers noted a reduction in triglyceride levels associated with pistachio consumption. This could be related to the fact that pistachios were often consumed in place of higher carbohydrate, lower fiber foods, which tend to raise triglycerides compared to higher fiber, higher fat foods like pistachios.^[2] In general, most triglycerides are carried in the blood by atherogenic (plaque forming) lipoproteins (e.g., VLDL), meaning that reducing triglyceride levels, all else being equal, is likely to reduce the risk of cardiovascular disease.^[3]

This study did not assess changes in LDL-C, but existing evidence suggests that pistachios can also reduce levels of this blood lipid. A 2020 network meta-analysis of RCTs found that eating pistachios reduced LDL levels by 6.6 mg/dL (0.17 mmol/L), an effect similar to, and even trending better than, eating several other types of tree nuts (walnuts, hazelnuts, cashews, and almonds).^[4] LDL-C, like triglycerides, is a marker for the number of atherogenic lipoproteins in the bloodstream.^[3] Pistachios reducing this lipid is another mechanism that could explain why eating pistachios may reduce the risk of cardiovascular disease.

Pistachios were reported to reduce systolic blood pressure by 2.89 mmHg. This may be attributable, in part, to the fact that pistachios are a good source of potassium (containing just under 300 mg of potassium per ounce), which has a well established blood-pressure-reducing effect.^[5] A 2.89 mmHg reduction is small, but for people with high blood pressure, reducing systolic blood pressure by even 5 mmHg seems to lower the risk of cardiovascular disease.^[6] It should be noted that none of the assessed trials were conducted specifically on people with high blood pressure. It’s possible pistachios may reduce blood pressure more among people with hypertension, similar to how strategies like sodium restriction and potassium supplementation^[7] function in people with hypertension, but this remains speculative.

There was a decrease in fasting glucose levels with pistachio intake, indicating an improvement in blood sugar regulation. At least one observational study, although it did not look at pistachios specifically, also seems consistent with the theory that pistachios may be helpful for glycemic control. That study, a prospective cohort study involving 83,818 women, found that eating an ounce of nuts at least five times per week was associated with a 29% lower risk of developing type 2 diabetes after adjusting for various potential confounders.^[8] Interestingly, this protective association was present regardless of BMI category (less than 25, 25-29, and at least 30). The mechanisms through which nuts like pistachios might benefit blood sugar control are unclear, but possibilities include the ability to reduce ceramides,^[9] increase adiponectin,^[10] and alter the gut microbiota.^[11]

Unfortunately, the existing research is not without shortcomings, as noted by the investigators in a risk-of-bias assessment. In most of the trials, it was unclear how investigators concealed the allocation of participants into study groups. This introduces the potential for differences between groups, which can affect study results.^[12] Furthermore, all trials were considered to be at high risk of having incomplete outcome data and selective reporting.

Finally, there are also some potential downsides to pistachios. Pistachios are notably high in FODMAPs, a class of poorly metabolized carbohydrates that often cause gastrointestinal problems in certain people.^[13] Eating pistachios, especially in large quantities, may result in adverse effects like abdominal pain and bloating in people sensitive to FODMAPs. Nuts with lower FODMAP levels include macadamia nuts, walnuts, and pecans. Another potential concern regarding pistachio intake is nut allergy. While pistachio allergies only affect a small percentage of the population (possibly less than 2%, although rates vary globally), people with an allergy can experience extreme reactions upon exposure, including anaphylaxis.^[14]

Examining the potential health benefits of pistachios Original paper