Pistachios — Benefits Deep Dive

The pistachio has been tested in clinical trials more often than most single foods, and the trials have looked at an unusually wide spread of the body: the protein and fiber in the nut itself, the pigment at the back of the eye, blood pressure and artery walls, blood sugar, the bacteria of the gut, body weight and the cholesterol carried in the blood. The seven articles below take each of those in turn. Each one reports what the studies measured, who took part, how much pistachio they ate and what was found — including the trials that found nothing — and each ends with what is still not known.

Most of these trials were small and lasted weeks or months rather than years, several were funded by nut-industry bodies, and none counted heart attacks, cases of diabetes or cases of eye disease. The findings are about measurements in the blood, the eye and the gut, and the articles keep that distinction in view throughout.

Deep-Dive Articles

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Protein and Fiber

How much protein and fiber an ounce of pistachios carries compared with other nuts, and how good the protein is by the two scoring systems nutrition scientists use. The only direct measurement, made in pigs, gave DIAAS scores of 86 for raw and 83 for roasted pistachios — a “good” protein, below the 100 line for “excellent” — and the page traces where the popular “complete protein” phrase comes from.

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Eye Health: Lutein and Zeaxanthin

Pistachios are the only common nut with a meaningful amount of lutein, the yellow pigment the eye collects in the macula, and laboratory analyses find lutein but no zeaxanthin. In one 12-week trial in 36 adults, two ounces a day raised macular pigment, a biomarker — no study has tested whether pistachios change the risk of any eye disease.

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Blood Pressure and Blood Vessels

Three meta-analyses each found systolic blood pressure about 2 to 3 mmHg lower with pistachios, with no change in diastolic pressure. The evidence on the artery wall is thinner: one three-month trial found less arterial stiffness, while the pooled analysis of artery widening found no clear effect.

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Blood Sugar and Diabetes

Eaten alone pistachios barely raise blood sugar, and eaten with bread, rice or pasta they flattened the rise in a dose-dependent way. The longer trials and four meta-analyses agree on a small fall in fasting glucose but disagree about fasting insulin, HOMA-IR and HbA1c, and no trial has counted new cases of diabetes.

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Gut Microbiome

What escapes digestion in a pistachio — fiber, fat held inside cell walls, and plant compounds — and what gut bacteria do with it. The human evidence is early: one small stool-sequencing study, a meta-analysis with a single pistachio trial, and a prediabetes trial that measured microbe-related chemicals in urine.

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Weight and Mindful Eating

A US government feeding study measured about 5 percent fewer absorbed calories than the label counts, and two single-session studies found people ate less when shells stayed in view or the nuts came in the shell. In the weight trials pistachios mostly did not cause the weight gain their calories would predict — a different finding from causing weight loss.

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Cholesterol and Lipids

The fat profile and plant sterols of the pistachio, and the controlled-feeding study in which two servings a day lowered LDL cholesterol by 11.6 percent. The pooled trials found smaller LDL and triglyceride reductions with strong disagreement between studies, and no trial has tested heart attacks or deaths.

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Table of Contents

  1. Deep-Dive Articles
  2. Why Pistachios Touch So Many Systems
  3. Research Papers: Protein and Fiber
  4. Research Papers: Eye Health
  5. Research Papers: Blood Pressure and Blood Vessels
  6. Research Papers: Blood Sugar and Diabetes
  7. Research Papers: Gut Microbiome
  8. Research Papers: Weight and Mindful Eating
  9. Research Papers: Cholesterol and Lipids
  10. Connections
  11. Featured Videos

Why Pistachios Touch So Many Systems

Most nuts are studied for their fat. The pistachio keeps turning up in trials of the eye, the gut, blood sugar and appetite as well, because it differs from the rest of the nut family in several measurable ways at once. Each difference points to a different part of the body, and each comes with its own limits.

More protein per calorie, and a better amino acid pattern than most nuts. A one-ounce handful (about 49 kernels) carries close to 6 grams of protein and 3 grams of fiber in about 160 calories. In the USDA figures almonds edge pistachios slightly on protein per ounce, so the popular claim that the pistachio is “the highest-protein nut” is not what the table shows — but because a pistachio is lower in fat than a pecan or macadamia, each calorie comes with more protein. Its protein also carries roughly twice the lysine, the amino acid plant proteins most often run short of, of almond or walnut protein. How well that protein is used has been measured only once, and in pigs rather than people: the DIAAS score (which rates protein by how much of each essential amino acid is absorbed) was 86 for raw and 83 for roasted pistachios, with lysine still the limiting amino acid. That clears the FAO’s 75-point line for a “good” protein but sits below the 100 line for “excellent”, and roasting lowered digestibility. The “complete protein” phrase traces mainly to a review commissioned by a pistachio growers’ trade association, in the looser sense that the nut contains all nine essential amino acids.

The only nut with real lutein. The green of the kernel comes partly from lutein, the yellow pigment the eye concentrates in the macula, the small central patch of the retina used for reading and fine detail. Per ounce, raw pistachios carry roughly 30 times the lutein of hazelnuts, the next nut on the USDA list, and laboratory analyses that separate the pigments find lutein but no zeaxanthin. Leafy greens still carry several times more, but the pistachio’s lutein arrives with fat, which lutein needs in order to be absorbed. In the one randomised trial that fed people pistachios and looked inside the eye, 36 healthy adults with low lutein intake ate two ounces a day for 12 weeks and their macular pigment rose. Macular pigment is a biomarker, not an eye-disease outcome: no trial has tested whether pistachios change the risk of macular degeneration or any other eye disease, and this single trial was supported in part by a pistachio growers’ association.

Potassium, and a modest effect on systolic pressure. At about 1,025 mg per 100 grams, pistachios are described in reviews as the most potassium-dense of the common nuts; a raw ounce carries roughly a tenth of the adult Adequate Intake listed by the NIH. Three meta-analyses of overlapping trials each found systolic pressure (the top number) about 2 to 3 mmHg lower with pistachios, and none found a change in diastolic pressure (the bottom number). Potassium, magnesium, arginine and unsaturated fat are all proposed explanations, but no trial has separated them, so these remain hypotheses. The evidence on the artery wall is weaker still: one small, unblinded three-month trial found less arterial stiffness, while the pooled analysis of flow-mediated dilation found no clear effect. Salting changes the sodium picture completely — from about 1 mg per 100 grams raw to 428 mg in the USDA salted entry — and the pooled analyses did not separate salted from unsalted trials.

Phytosterols and an unsaturated fat profile. Pistachios list about 214 mg of plant sterols per 100 grams, the highest of the common nuts in the reviews, and their fat is mostly monounsaturated and polyunsaturated. In a tightly controlled feeding study of 28 adults with raised LDL, two servings a day lowered LDL cholesterol by 11.6 percent against a lower-fat control diet, and blood beta-sitosterol rose, confirming that the sterols were absorbed. Pooled trials found a much smaller LDL reduction, about 3.8 mg/dL, along with lower triglycerides, and the trials disagreed strongly with one another. These are blood markers; no trial has tested whether pistachios reduce heart attacks, strokes or deaths.

The shell and the slower pace of eating. Most pistachios are sold in the shell, and that one feature has been studied on its own. In two single-session studies at one university, people ate 48 fewer calories of pistachios over a workday when the empty shells stayed in view, and 41 percent fewer calories during a class when the nuts came in the shell rather than shelled — without reporting feeling less full. Neither study followed what people ate afterwards or measured body weight.

Fewer calories absorbed than the label counts. Some of a pistachio’s fat stays locked inside plant cell walls that chewing does not break open, and passes through unabsorbed. A US Department of Agriculture feeding study of 16 adults measured the usable energy at about 5 percent below the label calculation — roughly 8 calories an ounce, a much smaller gap than the same group found for almonds. The fiber and trapped material that escape the small intestine travel on to the colon, which is the link to the gut-bacteria research: one small feeding study reported more butyrate-producing bacteria with pistachios, but the pooled nut trials contained only one pistachio trial, and no study has shown that these shifts change health.

What ties the findings together, and what holds them back. Protein, fat and fiber also slow the rise in blood sugar after a starchy meal, and in a ten-person study pistachios eaten with white bread cut the response at 56 and 84 grams, though not at 28 grams. In the weight trials, a daily portion of pistachios generally did not produce the gain its calories would predict, which is not the same as causing weight loss. The limits are shared across every article: the trials were small, ran for weeks or months, often had pistachios replacing other foods so part of any effect may come from what was removed, and several were funded by nut-industry bodies. People with a tree nut allergy — pistachio allergy is closely linked to cashew allergy — and people whose potassium intake is managed because of kidney disease are the groups each article names, and decisions in those situations belong with a clinician.

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Research Papers: Protein and Fiber

  1. Bailey HM, Stein HH. Raw and roasted pistachio nuts (Pistacia vera L.) are 'good' sources of protein based on their digestible indispensable amino acid score as determined in pigs. Journal of the Science of Food and Agriculture. 2020;100(10):3878-3885. PubMed PMID: 32323331
  2. Derbyshire E, Higgs J, Feeney MJ, et al. Believe It or 'Nut': Why It Is Time to Set the Record Straight on Nut Protein Quality: Pistachio (Pistacia vera L.) Focus. Nutrients. 2023;15(9). PubMed PMID: 37432263
  3. Dreher ML. Pistachio nuts: composition and potential health benefits. Nutrition Reviews. 2012;70(4):234-40. PubMed PMID: 22458696
  4. Bulló M, Juanola-Falgarona M, Hernández-Alonso P, et al. Nutrition attributes and health effects of pistachio nuts. The British Journal of Nutrition. 2015;113 Suppl 2:S79-93. PubMed PMID: 26148925
  5. Fantino M, Bichard C, Mistretta F, et al. Daily consumption of pistachios over 12 weeks improves dietary profile without increasing body weight in healthy women: A randomized controlled intervention. Appetite. 2020;144:104483. PubMed PMID: 31604062
  6. Carughi A, Bellisle F, Dougkas A, et al. A Randomized Controlled Pilot Study to Assess Effects of a Daily Pistachio (Pistacia Vera) Afternoon Snack on Next-Meal Energy Intake, Satiety, and Anthropometry in French Women. Nutrients. 2019;11(4). PubMed PMID: 30986958
  7. Costa J, Silva I, Vicente AA, et al. Pistachio nut allergy: An updated overview. Critical Reviews in Food Science and Nutrition. 2019;59(4):546-562. PubMed PMID: 28925724

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Research Papers: Eye Health

  1. Scott TM, Ogunbodede O, McKay DL, et al. Pistachio Consumption Increases Macular Pigment Optical Density in Healthy Adults: A Randomized Controlled Trial. The Journal of Nutrition. 2025;155(1):168-174. PubMed PMID: 39426460
  2. Eisenhauer B, Natoli S, Liew G, et al. Lutein and Zeaxanthin-Food Sources, Bioavailability and Dietary Variety in Age-Related Macular Degeneration Protection. Nutrients. 2017;9(2). PubMed PMID: 28208784
  3. Dreher ML. Pistachio nuts: composition and potential health benefits. Nutrition Reviews. 2012;70(4):234-40. PubMed PMID: 22458696
  4. Bulló M, Juanola-Falgarona M, Hernández-Alonso P, et al. Nutrition attributes and health effects of pistachio nuts. The British Journal of Nutrition. 2015;113 Suppl 2:S79-93. PubMed PMID: 26148925
  5. Terzo S, Baldassano S, Caldara GF, et al. Health benefits of pistachios consumption. Natural Product Research. 2019;33(5):715-726. PubMed PMID: 29241364
  6. Mandalari G, Barreca D, Gervasi T, et al. Pistachio Nuts (Pistacia vera L.): Production, Nutrients, Bioactives and Novel Health Effects. Plants (Basel). 2021;11(1). PubMed PMID: 35009022

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Research Papers: Blood Pressure and Blood Vessels

  1. Asbaghi O, Hadi A, Campbell MS, et al. Effects of pistachios on anthropometric indices, inflammatory markers, endothelial function and blood pressure in adults: a systematic review and meta-analysis of randomised controlled trials. The British Journal of Nutrition. 2021;126(5):718-729. PubMed PMID: 33198823
  2. Ghanavati M, Rahmani J, Clark CCT, et al. Pistachios and cardiometabolic risk factors: A systematic review and meta-analysis of randomized controlled clinical trials. Complementary Therapies in Medicine. 2020;52:102513. PubMed PMID: 32951758
  3. Baghery F, Mohammadifard N, Khanamani Falahati-Pour S. The effect of pistachio supplementation on metabolic syndrome and its components in adults: a systematic review and meta-analysis of randomized controlled trials. Nutrition Reviews. 2022;80(10):2051-2063. PubMed PMID: 35689651
  4. Baghery F, Mohammadifard N, Khanamani Falahati-Pour S. Reply to Letter to the editor regarding "The effect of pistachio supplementation on metabolic syndrome and its components in adults: a systematic review and meta-analysis of randomized controlled trials". Nutrition Reviews. 2024;82(5):711-713. PubMed PMID: 37550254
  5. Kasliwal RR, Bansal M, Mehrotra R, et al. Effect of pistachio nut consumption on endothelial function and arterial stiffness. Nutrition. 2015;31(5):678-85. PubMed PMID: 25837212
  6. Kendall CW, West SG, Augustin LS, et al. Acute effects of pistachio consumption on glucose and insulin, satiety hormones and endothelial function in the metabolic syndrome. European Journal of Clinical Nutrition. 2014;68(3):370-5. PubMed PMID: 24424074
  7. Rock CL, Zunshine E, Nguyen HT, et al. Effects of Pistachio Consumption in a Behavioral Weight Loss Intervention on Weight Change, Cardiometabolic Factors, and Dietary Intake. Nutrients. 2020;12(7). PubMed PMID: 32698457
  8. Edwards K, Kwaw I, Matud J, et al. Effect of pistachio nuts on serum lipid levels in patients with moderate hypercholesterolemia. Journal of the American College of Nutrition. 1999;18(3):229-32. PubMed PMID: 10376778

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Research Papers: Blood Sugar and Diabetes

  1. Kendall CW, Josse AR, Esfahani A, et al. The impact of pistachio intake alone or in combination with high-carbohydrate foods on post-prandial glycemia. European Journal of Clinical Nutrition. 2011;65(6):696-702. PubMed PMID: 21364607
  2. Kendall CW, West SG, Augustin LS, et al. Acute effects of pistachio consumption on glucose and insulin, satiety hormones and endothelial function in the metabolic syndrome. European Journal of Clinical Nutrition. 2014;68(3):370-5. PubMed PMID: 24424074
  3. Gulati S, Misra A, Pandey RM, et al. Effects of pistachio nuts on body composition, metabolic, inflammatory and oxidative stress parameters in Asian Indians with metabolic syndrome: a 24-wk, randomized control trial. Nutrition. 2014;30(2):192-7. PubMed PMID: 24377454
  4. Hernández-Alonso P, Salas-Salvadó J, Baldrich-Mora M, et al. Beneficial effect of pistachio consumption on glucose metabolism, insulin resistance, inflammation, and related metabolic risk markers: a randomized clinical trial. Diabetes Care. 2014;37(11):3098-105. PubMed PMID: 25125505
  5. Ghanavati M, Rahmani J, Clark CCT, et al. Pistachios and cardiometabolic risk factors: A systematic review and meta-analysis of randomized controlled clinical trials. Complementary Therapies in Medicine. 2020;52:102513. PubMed PMID: 32951758
  6. Nowrouzi-Sohrabi P, Hassanipour S, Sisakht M, et al. The effectiveness of pistachio on glycemic control and insulin sensitivity in patients with type 2 diabetes, prediabetes and metabolic syndrome: A systematic review and meta-analysis. Diabetes & Metabolic Syndrome. 2020;14(5):1589-1595. PubMed PMID: 32947760
  7. Baghery F, Mohammadifard N, Khanamani Falahati-Pour S. The effect of pistachio supplementation on metabolic syndrome and its components in adults: a systematic review and meta-analysis of randomized controlled trials. Nutrition Reviews. 2022;80(10):2051-2063. PubMed PMID: 35689651
  8. Hadi A, Asbaghi O, Kazemi M, et al. Effects of pistachios on glycaemic control: a systematic review and meta-analysis of randomised controlled trials. The British Journal of Nutrition. 2023;129(10):1693-1702. PubMed PMID: 35795961

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Research Papers: Gut Microbiome

  1. Creedon AC, Hung ES, Berry SE, et al. Nuts and their Effect on Gut Microbiota, Gut Function and Symptoms in Adults: A Systematic Review and Meta-Analysis of Randomised Controlled Trials. Nutrients. 2020;12(8). PubMed PMID: 32781516
  2. Hernández-Alonso P, Cañueto D, Giardina S, et al. Effect of pistachio consumption on the modulation of urinary gut microbiota-related metabolites in prediabetic subjects. The Journal of Nutritional Biochemistry. 2017;45:48-53. PubMed PMID: 28432876
  3. Hernández-Alonso P, Giardina S, Salas-Salvadó J, et al. Chronic pistachio intake modulates circulating microRNAs related to glucose metabolism and insulin resistance in prediabetic subjects. European Journal of Nutrition. 2017;56(6):2181-2191. PubMed PMID: 27383196
  4. Prapa I, Yanni AE, Kompoura V, et al. Functional Modulation of Gut Microbiota and Blood Parameters in Diabetic Rats Following Dietary Intervention with Free or Immobilized Pediococcus acidilactici SK Cells on Pistachio Nuts. Nutrients. 2024;16(23). PubMed PMID: 39683613
  5. Dreher ML. Pistachio nuts: composition and potential health benefits. Nutrition Reviews. 2012;70(4):234-40. PubMed PMID: 22458696
  6. Mandalari G, Barreca D, Gervasi T, et al. Pistachio Nuts (Pistacia vera L.): Production, Nutrients, Bioactives and Novel Health Effects. Plants. 2021;11(1). PubMed PMID: 35009022
  7. Mateos R, Salvador MD, Fregapane G, et al. Why Should Pistachio Be a Regular Food in Our Diet? Nutrients. 2022;14(15). PubMed PMID: 35956383

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Research Papers: Weight and Mindful Eating

  1. Baer DJ, Gebauer SK, Novotny JA. Measured energy value of pistachios in the human diet. Br J Nutr. 2012;107(1):120-5. PubMed PMID: 21733319
  2. Kennedy-Hagan K, Painter JE, Honselman C, et al. The effect of pistachio shells as a visual cue in reducing caloric consumption. Appetite. 2011;57(2):418-20. PubMed PMID: 21704666
  3. Honselman CS, Painter JE, Kennedy-Hagan KJ, et al. In-shell pistachio nuts reduce caloric intake compared to shelled nuts. Appetite. 2011;57(2):414-7. PubMed PMID: 21645565
  4. Fantino M, Bichard C, Mistretta F, et al. Daily consumption of pistachios over 12 weeks improves dietary profile without increasing body weight in healthy women: A randomized controlled intervention. Appetite. 2020;144:104483. PubMed PMID: 31604062
  5. Carughi A, Bellisle F, Dougkas A, et al. A Randomized Controlled Pilot Study to Assess Effects of a Daily Pistachio (Pistacia Vera) Afternoon Snack on Next-Meal Energy Intake, Satiety, and Anthropometry in French Women. Nutrients. 2019;11(4). PubMed PMID: 30986958
  6. Li Z, Song R, Nguyen C, et al. Pistachio nuts reduce triglycerides and body weight by comparison to refined carbohydrate snack in obese subjects on a 12-week weight loss program. Journal of the American College of Nutrition. 2010;29(3):198-203. PubMed PMID: 20833992
  7. Rock CL, Zunshine E, Nguyen HT, et al. Effects of Pistachio Consumption in a Behavioral Weight Loss Intervention on Weight Change, Cardiometabolic Factors, and Dietary Intake. Nutrients. 2020;12(7). PubMed PMID: 32698457
  8. Asbaghi O, Hadi A, Campbell MS, et al. Effects of pistachios on anthropometric indices, inflammatory markers, endothelial function and blood pressure in adults: a systematic review and meta-analysis of randomised controlled trials. The British Journal of Nutrition. 2021;126(5):718-729. PubMed PMID: 33198823

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Research Papers: Cholesterol and Lipids

  1. Gebauer SK, West SG, Kay CD, et al. Effects of pistachios on cardiovascular disease risk factors and potential mechanisms of action: a dose-response study. Am J Clin Nutr. 2008;88(3):651-9. PubMed PMID: 18779280
  2. Kay CD, Gebauer SK, West SG, et al. Pistachios increase serum antioxidants and lower serum oxidized-LDL in hypercholesterolemic adults. J Nutr. 2010;140(6):1093-8. PubMed PMID: 20357077
  3. Holligan SD, West SG, Gebauer SK, et al. A moderate-fat diet containing pistachios improves emerging markers of cardiometabolic syndrome in healthy adults with elevated LDL levels. The British Journal of Nutrition. 2014;112(5):744-52. PubMed PMID: 25008473
  4. Edwards K, Kwaw I, Matud J, et al. Effect of pistachio nuts on serum lipid levels in patients with moderate hypercholesterolemia. Journal of the American College of Nutrition. 1999;18(3):229-32. PubMed PMID: 10376778
  5. Hadi A, Asbaghi O, Kazemi M, et al. Consumption of pistachio nuts positively affects lipid profiles: A systematic review and meta-analysis of randomized controlled trials. Critical Reviews in Food Science and Nutrition. 2023;63(21):5358-5371. PubMed PMID: 34933637
  6. Lippi G, Cervellin G, Mattiuzzi C. More pistachio nuts for improving the blood lipid profile. Systematic review of epidemiological evidence. Acta Bio-Medica. 2016;87(1):5-12. PubMed PMID: 27163889
  7. Liu K, Hui S, Wang B, et al. Comparative effects of different types of tree nut consumption on blood lipids: a network meta-analysis of clinical trials. The American Journal of Clinical Nutrition. 2020;111(1):219-227. PubMed PMID: 31773150
  8. Nishi SK, Paz-Graniel I, Ni J, et al. Effect of nut consumption on blood lipids: An updated systematic review and meta-analysis of randomized controlled trials. Nutrition, Metabolism, and Cardiovascular Diseases. 2025;35(5):103771. PubMed PMID: 39638677

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Connections

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