Pistachios: Blood Pressure and Blood Vessels

Table of Contents

1. What a Pistachio Brings to a Blood Vessel
2. Salted and Unsalted: The Sodium Numbers
3. Candidate Mechanisms (Hypotheses)
4. The Three Pooled Blood-Pressure Analyses
5. Individual Trials That Measured Blood Pressure
6. Artery Widening and Stiffness Over Three Months
7. The Single-Meal Vascular Test
8. Inflammation and Oxidative Stress Markers
9. Who Was Studied
10. Heart-Rate Variability, Stress Responses and Erectile Function
11. What Is Not Known
12. Who the Research Raises Concerns For
13. Connections
14. Key Research Papers
15. Featured Videos

What a Pistachio Brings to a Blood Vessel

The figures below come from the USDA FoodData Central database (SR Legacy entries) for raw pistachio kernels, dry-roasted kernels without added salt and dry-roasted kernels with salt added. The one-ounce column is the per-100-gram value multiplied by 0.2835 (one ounce is 28.35 g, roughly 49 shelled kernels) and rounded.

For scale: the NIH Office of Dietary Supplements lists an Adequate Intake for potassium of 3,400 mg a day for adult men and 2,600 mg for adult women, and a Recommended Dietary Allowance for magnesium of 400–420 mg for adult men and 310–320 mg for adult women. A one-ounce handful of raw pistachios therefore carries roughly a tenth of the potassium figure and a tenth of the magnesium figure. Reviews of pistachio composition describe it as the richest of the common nuts in potassium, and also high in γ-tocopherol (a form of vitamin E), phytosterols and the carotenoids lutein and zeaxanthin [Dreher 2012; Bulló 2015; Terzo 2019].

The fat is mostly unsaturated: in the raw entry, monounsaturated and polyunsaturated fat together make up about 83 percent of the total fat, and saturated fat about 13 percent.

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Salted and Unsalted: The Sodium Numbers

The pistachio kernel itself contains almost no sodium: the USDA lists 1 mg per 100 grams raw and 6 mg per 100 grams dry-roasted without salt. Salting changes that completely. The USDA entry for dry-roasted pistachios with salt added lists 428 mg of sodium per 100 grams, which works out to about 121 mg in a one-ounce serving. The FDA's Daily Value for sodium is 2,300 mg, so one salted ounce supplies roughly 5 percent of it. Salt content on real packages varies by product; the label is the source for any particular bag.

The potassium does not change with salting (1,007 mg per 100 grams in both roasted entries), so the ratio of potassium to sodium — often discussed in blood-pressure research — drops from about 1,000 to 1 in the raw nut to a little over 2 to 1 in the salted roasted nut.

Most pistachio trials did not report whether the nuts were salted. Two in this page's reference set did: the Indian metabolic-syndrome trial gave unsalted pistachios [Gulati 2014], and a 12-week weight-loss trial gave 53 g of salted pistachios a day as an afternoon snack, compared with salted pretzels [Li 2010]. The abstract of the salted trial reports weight, body-mass index, triglycerides and cholesterol, and does not report blood pressure, so it says nothing either way about how salted pistachios affect blood pressure. The pooled analyses below did not separate salted from unsalted trials.

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Candidate Mechanisms (Hypotheses)

None of the pistachio trials in this page's reference set was designed to show which component of the nut moves blood pressure. The explanations below are hypotheses drawn from what is known about each nutrient and from review articles on pistachios; they are not findings of the pistachio trials themselves.

Potassium

Potassium helps the kidneys excrete sodium and helps the smooth muscle in artery walls relax. Higher potassium intake is associated with lower blood pressure in the general nutrition literature (see the Potassium and Blood Pressure page). Pistachios are the most potassium-dense of the common nuts [Dreher 2012; Bulló 2015], which makes potassium the most often proposed explanation for the systolic findings. Whether the roughly 290 mg in a one-ounce serving, or the larger amounts used in trials, is enough to account for a 2–3 mmHg change has not been tested directly.

Magnesium

Magnesium takes part in the contraction and relaxation of blood-vessel muscle. Pistachios supply a moderate amount (about 34 mg per ounce raw). No pistachio trial in the reference set separated a magnesium effect from the rest of the nut.

Arginine and nitric oxide

Arginine is an amino acid that the inner lining of blood vessels (the endothelium) uses to make nitric oxide, a signal that tells the vessel wall to relax and widen (see Nitric Oxide and How Blood Vessels Relax). Pistachios contain about 2.1 g of arginine per 100 grams, roughly 0.6 g per ounce. Whether food amounts of arginine raise nitric-oxide production enough to change blood pressure or artery function is an open question; the pistachio trials did not measure nitric oxide.

Polyphenols, carotenoids and unsaturated fat

Pistachios contain phenolic acids, flavonoids and anthocyanins (which give the skin its purple colour) as well as lutein and γ-tocopherol. Reviews describe antioxidant and anti-inflammatory effects of pistachio polyphenols, demonstrated mainly in laboratory (cell-culture) and animal studies, with some support from clinical trials [Mandalari 2021; Mateos 2022]. Oxidative stress and inflammation in the artery wall reduce the endothelium's ability to make nitric oxide, so these compounds are proposed as a route to better endothelial function. The unsaturated fat replacing saturated fat or refined carbohydrate in the diet is another proposed route. Each of these is a plausible pathway, not a demonstrated cause.

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The Three Pooled Blood-Pressure Analyses

A meta-analysis combines the results of several randomised controlled trials (trials in which participants are assigned by chance to eat pistachios or not) to get a more precise estimate than any single small trial can give. Three have looked at pistachios and blood pressure. They searched the literature at different times and drew largely on the same pool of trials, so they are best read as three looks at overlapping evidence rather than three independent confirmations.

Ghanavati and colleagues (2020) pooled 11 trials with 506 participants and reported a systolic reduction of 3.10 mmHg. The I² figure of 63 percent means the individual trials disagreed with each other considerably about the size of the effect. The authors stated they saw no adverse effect of pistachios on body-mass index or blood pressure, and wrote that the effect of different pistachio doses, and whether pistachios prevent endothelial dysfunction, remained unclear [Ghanavati 2020].

Asbaghi and colleagues (2021) pooled 13 trials with 563 participants. Systolic pressure fell by 2.12 mmHg. Diastolic pressure, flow-mediated dilation (an ultrasound measure of how much the arm artery widens after a cuff is released, a standard test of endothelial function), C-reactive protein, TNF-α, body weight, body-mass index and waist circumference did not change significantly. The authors concluded that pistachios reduced systolic pressure and called for larger studies [Asbaghi 2021].

Baghery and colleagues (2022) pooled 17 trials with 940 adults on the components of metabolic syndrome. Systolic pressure fell by 2.89 mmHg; diastolic pressure, waist circumference and body-mass index did not change considerably [Baghery 2022]. A letter to the editor later questioned how the effect sizes were calculated, including the use of several effect sizes from a single study. In their published reply the authors defended the approach, reanalysed the data using an assumed correlation coefficient of 0.5, and kept their conclusion [Baghery 2024 reply]. The letter's own text is not in this page's reference set, so its full argument is not reported here.

Taken together, the three analyses agree on a modest systolic reduction of about 2 to 3 mmHg and no diastolic change. None of them reported a clear improvement in flow-mediated dilation.

Pooled analyses that compare different types of nuts for blood pressure have also been published. None is in the verified reference set behind this page, so this page does not report their numbers; a PubMed topic search for them is listed at the bottom.

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Individual Trials That Measured Blood Pressure

Two individual trials in this page's reference set report blood pressure in their abstracts. One found a reduction; one found none.

Weight-loss programme, overweight and obese adults (Rock 2020)

One hundred overweight or obese adults without diabetes took part in a four-month behavioural weight-loss programme. Half were also given 42 g (1.5 oz) of pistachios a day. Weight loss was similar in both groups (about 5 percent). The pistachio group, but not the control group, showed a significant reduction in both systolic and diastolic blood pressure over time (time effect p = 0.01). The abstract reports this as a change within the pistachio group; it does not report a direct comparison of blood pressure between the two groups. Blood levels of alpha-carotene, beta-carotene and lutein rose in the pistachio group, and fibre intake went up while sweets intake went down [Rock 2020].

Moderately high cholesterol, three weeks (Edwards 1999)

Ten people with moderately high cholesterol took part in a randomised crossover trial in which pistachios supplied 20 percent of daily calories for three weeks. Total cholesterol fell, but body weight and blood pressure “remained constant throughout the study” [Edwards 1999]. With ten participants and three weeks, the trial could only have detected a large change in blood pressure.

Trials whose abstracts do not report blood pressure

Several other pistachio trials in the reference set — the 24-week metabolic-syndrome trial in India [Gulati 2014], the controlled-feeding trial in adults with elevated LDL cholesterol [Holligan 2014], the 12-week salted-pistachio weight-loss trial [Li 2010] and the four-month prediabetes crossover trial [Canudas 2019] — do not report blood pressure in their abstracts. Some of them may have measured it and contributed data to the pooled analyses; the abstracts alone do not say.

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Artery Widening and Stiffness Over Three Months

The most detailed vascular trial in the reference set comes from Kasliwal and colleagues (2015). Sixty adults with mild dyslipidaemia (moderately abnormal blood fats) were randomised to lifestyle modification alone — diet and exercise advice — or lifestyle modification plus 80 g of in-shell pistachios a day (equivalent to 40 g, or 1.5 oz, of shelled kernels) for three months. The trial was open-label, meaning participants and investigators knew who was eating pistachios.

Two kinds of vascular measurement were taken before and after:

• Brachial artery flow-mediated dilation (FMD) — how much the main arm artery widens after blood flow is briefly cut off and restored, a measure of endothelial function.
• Pulse wave velocity (PWV) — how fast the pressure wave from each heartbeat travels between two points (carotid to femoral artery, and brachial to ankle). A stiffer artery carries the wave faster, so a lower number means less stiff arteries.

Results reported in the abstract:

• The lifestyle-only group showed no change in any clinical, biochemical or vascular measure.
• In the pistachio group, left brachial-ankle PWV fell from 1,261.7 to 1,192.4 cm/sec (P = 0.02). Most other vascular measures, including FMD, improved but not to a statistically significant degree within the group.
• At three months, compared with the lifestyle-only group, the pistachio group had lower carotid-femoral PWV (770.9 vs 846.4 cm/sec, P = 0.08), lower left brachial-ankle PWV (1,192.4 vs 1,326.3 cm/sec, P = 0.05) and lower average brachial-ankle PWV (1,208.2 vs 1,295.8 cm/sec, P = 0.08).
• A two-way analysis of variance found a significant effect of pistachio treatment on carotid-femoral PWV, left brachial-ankle PWV and FMD (P = 0.037, 0.01 and 0.046), with average brachial-ankle PWV at P = 0.07.
• HDL cholesterol rose (35.7 to 37.8 mg/dL), LDL cholesterol fell (137.2 to 127.6 mg/dL) and fasting blood sugar fell slightly (88.8 to 86.6 mg/dL) in the pistachio group.

The authors concluded that regular pistachio consumption improved arterial stiffness and endothelial function. Several of the head-to-head comparisons sat at or just above the conventional P = 0.05 threshold, the trial was small and unblinded, and it ran for three months. The pooled FMD estimate across trials [Asbaghi 2021] did not find a significant effect, so this trial's FMD result has not been confirmed by the wider body of evidence.

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The Single-Meal Vascular Test

Kendall and colleagues (2014) tested what happens in the hours after a single meal. Twenty people with metabolic syndrome ate five different test meals, one per visit, over five to ten weeks (a randomised crossover design, in which each person serves as their own comparison). The meals were matched for available carbohydrate: three had 50 g (white bread alone; white bread with butter and cheese; white bread with pistachios) and two had 12 g (a small amount of white bread alone; pistachios alone).

Endothelial function was measured with the reactive hyperaemia index (a fingertip measure of blood-flow response) and arterial stiffness with the augmentation index (how much the reflected pressure wave adds to the main pulse). The abstract reports that both measures rose after the white-bread-only meals compared with the bread, butter and cheese meal. It does not report a vascular difference attributable specifically to the pistachio meals. The main pistachio findings in this trial were metabolic: a lower blood-sugar rise after the meal and higher levels of the gut hormone GLP-1 compared with white bread [Kendall 2014].

A single-meal test measures a response over a few hours. It does not show what happens to blood vessels over months of regular eating, and the abstract's vascular result is a contrast between bread meals rather than a pistachio effect.

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Inflammation and Oxidative Stress Markers

Inflammation and oxidative damage in the artery wall are part of how blood vessels stiffen and how atherosclerosis develops, so several pistachio trials measured blood markers of both. The results are mixed.

• Single trial, positive: in the 24-week Indian trial in 60 adults with metabolic syndrome, unsalted pistachios supplying 20 percent of daily energy, added to a diet and exercise programme, were followed by significant improvements compared with control in high-sensitivity C-reactive protein, TNF-α, TBARS (a marker of fat oxidation), adiponectin, waist circumference, fasting blood sugar, total cholesterol and LDL cholesterol [Gulati 2014].
• Pooled, null: across 13 trials, C-reactive protein (pooled difference 0.00 mg/l) and TNF-α (−0.09 pg/ml) did not change significantly [Asbaghi 2021].
• Pooled, positive for one oxidation marker: malondialdehyde (MDA), a product of fat oxidation, fell (pooled difference −0.36, I² 0%) [Ghanavati 2020].
• DNA oxidation: in a four-month crossover trial in 49 adults with prediabetes, a diet including 57 g of pistachios a day was followed by lower oxidative damage to DNA than an isocaloric control diet (reported P = 0.009) and higher expression of two telomere-related genes [Canudas 2019].
• Controlled feeding, elevated LDL: in 28 adults with elevated LDL cholesterol, a diet with two servings of pistachios a day lowered small dense LDL particles and the triglyceride-to-HDL ratio compared with a lower-fat control diet; some measures of HDL function improved only in people whose C-reactive protein was low at the start [Holligan 2014].

These are markers, not events: none of these trials measured heart attacks, strokes or deaths.

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Who Was Studied

People with diabetes. No trial in this page's reference set measured blood pressure or blood-vessel function in people with diagnosed type 2 diabetes eating pistachios. The diabetes-related trials here enrolled people with prediabetes or metabolic syndrome, and their abstracts report blood sugar, insulin and molecular markers rather than blood pressure [Canudas 2019; Kendall 2014]. The Pistachios: Blood Sugar and Diabetes page covers those results.

People with high blood pressure. None of the individual trials in the reference set selected participants because they had hypertension. The systolic reductions in the pooled analyses come mostly from people with raised cholesterol, metabolic syndrome or excess weight.

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Heart-Rate Variability, Stress Responses and Erectile Function

Other vascular questions are asked about nuts and pistachios: 24-hour (ambulatory) blood pressure, heart-rate variability (beat-to-beat changes in heart rhythm, a window on the nervous system's control of the heart), blood-pressure and vascular responses to laboratory stress tests, and erectile function as a measure of blood flow. No trial measuring any of these is in the verified reference set behind this page. Because every study claim on this page comes from an abstract that has been read and checked, no designs or numbers are reported for them here. PubMed topic searches for each are listed under Key Research Papers for readers who want to look at the original studies.

The reviews in the reference set mention endothelial function among the areas of pistachio research but do not describe heart-rate variability, stress testing or erectile function [Dreher 2012; Terzo 2019; Mateos 2022].

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What Is Not Known

• Which component matters. Potassium, magnesium, arginine, polyphenols and unsaturated fat are all proposed explanations; no pistachio trial has separated them.
• Dose. Trials used anywhere from about 40 g a day to 20 percent of daily calories. The Ghanavati analysis named the effect of different doses as an open question [Ghanavati 2020].
• Salted versus unsalted. The pooled analyses did not separate the two, and the one salted-pistachio trial in the reference set did not report blood pressure in its abstract [Li 2010]. Whether the sodium in salted pistachios offsets the systolic reduction seen with pistachios in general has not been tested in the trials here.
• Diastolic pressure. All three pooled analyses found no diastolic change; why systolic but not diastolic pressure moves is not explained.
• Endothelial function. One three-month trial found an FMD effect [Kasliwal 2015]; the pooled estimate did not [Asbaghi 2021]. Whether pistachios improve endothelial function remains unsettled.
• Long-term outcomes. All the trials ran from three weeks to six months and measured blood pressure, stiffness or blood markers. None counted heart attacks, strokes or deaths.
• What pistachios replaced. In most trials pistachios replaced other foods (bread, pretzels, other fats or the usual diet). Part of any effect may come from what was taken out rather than what was added.
• Size and design. Many trials were small, some were unblinded, and the pooled analyses showed substantial heterogeneity (I² 63% for systolic pressure in Ghanavati 2020).

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Who the Research Raises Concerns For

• People with a pistachio or cashew allergy. Pistachio can trigger moderate to severe IgE-mediated allergic reactions, and pistachio allergy is closely linked with cashew allergy; five pistachio allergens are officially listed [Costa 2019]. In a cashew oral-immunotherapy study, every one of 35 pistachio-co-allergic patients desensitised to cashew was also cross-desensitised to pistachio, which illustrates how closely the two allergies are tied [Elizur 2022].
• People on potassium-restricted diets. At about 1,000 mg of potassium per 100 grams, pistachios are a concentrated potassium source. Advanced kidney disease and some blood-pressure medicines (including ACE inhibitors, angiotensin receptor blockers and potassium-sparing diuretics) raise blood potassium, and diets in those situations are often managed with a clinician (see Kidney Disease).
• People limiting sodium. Salted pistachios carry about 121 mg of sodium per ounce according to the USDA salted entry; unsalted kernels carry almost none.
• Calories. Pistachios provide about 159 kcal per ounce. The weight-loss and snack trials in the reference set did not find weight gain at 42–56 g a day [Rock 2020; Li 2010; Fantino 2020].

Decisions about blood-pressure treatment, potassium intake in kidney disease or allergy testing belong with a clinician.

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Connections

• Nuts — the nuts landing page
• Pistachios — the main topic page
• Pistachios — Benefits Deep Dive — the hub for this series
• Pistachios: Nutrient Profile — the full composition table
• Protein and Fiber
• Cholesterol and Lipids
• Blood Sugar and Diabetes
• Weight and Mindful Eating
• Gut Microbiome
• Eye Health: Lutein and Zeaxanthin
• Hypertension — high blood pressure
• Potassium — the mineral pistachios carry most of
• Potassium and Blood Pressure
• Magnesium for Heart Health
• Arginine — the nitric oxide precursor
• Arginine: Cardiovascular and Nitric Oxide
• Nitric Oxide and How Blood Vessels Relax — animation
• Salt Excess and High Blood Pressure
• Atherosclerosis
• Metabolic Syndrome — the group in several pistachio trials
• Peanuts: Heart Health and Mortality
• Dark Chocolate: Flavanols and Endothelial Function

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Key Research Papers

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
9. 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
10. 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
11. Canudas S, Hernández-Alonso P, Galié S, et al. Pistachio consumption modulates DNA oxidation and genes related to telomere maintenance: a crossover randomized clinical trial. The American Journal of Clinical Nutrition. 2019;109(6):1738-1745. PubMed PMID: 31051499
12. 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
13. 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
14. Dreher ML. Pistachio nuts: composition and potential health benefits. Nutrition Reviews. 2012;70(4):234-40. PubMed PMID: 22458696
15. 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
16. Terzo S, Baldassano S, Caldara GF, et al. Health benefits of pistachios consumption. Natural Product Research. 2019;33(5):715-726. PubMed PMID: 29241364
17. 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
18. 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
19. 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
20. Elizur A, Appel MY, Nachshon L, et al. Cashew oral immunotherapy for desensitizing cashew-pistachio allergy (NUT CRACKER study). Allergy. 2022;77(6):1863-1872. PubMed PMID: 35000223

PubMed Topic Searches

1. PubMed: pistachios and blood pressure in randomised trials
2. PubMed: pistachios and 24-hour ambulatory blood pressure
3. PubMed: pistachios and heart-rate variability
4. PubMed: pistachios and vascular responses to stress
5. PubMed: pistachios, endothelial function and flow-mediated dilation
6. PubMed: pistachios and erectile function
7. PubMed: nut consumption and blood pressure meta-analyses
8. PubMed: dietary potassium and blood pressure meta-analyses

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