Can Pistachios Help With Diabetes? What a 2009 Rat Study Found

What Did the 2009 Istanbul Study Test?

The study set out to test whether pistachios, widely eaten in Anatolia, lower blood glucose and support antioxidant defences in diabetic rats. Three biochemists from Istanbul University and Marmara University published it in 2009 in the Firat University Medical Journal of Health Sciences (Alturfan et al., 2009).

The researchers used 32 Wistar albino rats aged eight weeks, divided into four groups of eight with equal numbers of males and females (Alturfan et al., 2009). In the study, two groups of rats were made diabetic with a single injection of streptozotocin (45 mg/kg), a compound that destroys the insulin-producing beta cells of the pancreas (Alturfan et al., 2009; Furman, 2021). Rats with glucose above 11 mmol/L two days later were included; the control groups got only the citrate buffer (Alturfan et al., 2009).

One healthy group and one diabetic group then ate standard chow with 1.26% pistachio added for eight weeks, an amount the authors scaled from a human intake of 10 oz to a 200 g rat; the paper does not state how much chow each rat ate (Alturfan et al., 2009).

What was measured

After an overnight fast, blood was drawn from the heart under anaesthesia (Alturfan et al., 2009). The team measured glucose, sialic acid as a marker of tissue damage, and five markers of oxidative balance, among them total antioxidant activity, superoxide dismutase, glutathione and TBARS from oxidised fats (Alturfan et al., 2009).

The study measured no insulin and no HbA1c or other marker of glycation, the binding of sugars to proteins, and it does not describe its glucose assay or report funding (Alturfan et al., 2009).

What Did the Study Find?

In diabetic rats, the pistachio diet made no significant difference to blood glucose. The untreated diabetic group averaged 21.94 mmol/L and the pistachio-fed diabetic group 19.87 mmol/L, about 9% lower, and the authors describe the fall as insignificant (Alturfan et al., 2009). Both diabetic groups stayed at roughly four times the healthy controls’ 5.03 mmol/L (Alturfan et al., 2009).

The changes the authors report as significant were in two blood markers. Compared with untreated diabetic rats, TBARS fell from 5.86 to 3.99 nmol/mL, about 32% lower, and total antioxidant activity rose from 1.12 to 1.42 mmol/L, about 27% higher (Alturfan et al., 2009). Superoxide dismutase, glutathione and protein thiols rose slightly and sialic acid fell, but none of these differences was significant (Alturfan et al., 2009). Put simply, the pistachio-fed diabetic rats looked less oxidatively stressed on two tests, while their blood sugar stayed high (Alturfan et al., 2009).

Table 1. Blood markers in the four rat groups after the pistachio diet, as printed in the 2009 paper

Table note: Values are mean ± SEM, eight rats per group (Alturfan et al., 2009). Letters (a), (b) and (c) mark differences from healthy controls at P<0.05, P<0.01 and P<0.001, and (d) from untreated diabetic rats at P<0.05 (Alturfan et al., 2009).

The authors’ interpretation is hedged. They propose that pistachio may mop up free radicals generated by streptozotocin and could be added to diets to reduce oxidative stress in diabetes, but call for longer studies (Alturfan et al., 2009). The abstract is bolder, claiming a benefit to diabetic risk factors “in a dose-dependent manner”, although only one pistachio level was tested (Alturfan et al., 2009).

Why Can’t a Rat Study Answer the Human Question?

Streptozotocin produces a different disease from the one most people have. The compound destroys insulin-producing beta cells and is widely used as a model of type 1 diabetes, while type 2 models need separate protocols (Furman, 2021). More than 90% of people with diabetes have type 2, and the International Diabetes Federation estimates that about 589 million adults aged 20 to 79 were living with diabetes in 2024 (International Diabetes Federation, 2025).

The study’s positive results also rest on tests that specialists now treat with caution. A 2022 consensus on measuring oxidative damage advises against using TBARS or total antioxidant activity in clinical studies, partly because thiobarbituric acid reacts with many molecules besides malondialdehyde (Murphy et al., 2022). Here the antioxidant-activity method itself generates TBARS, so both headline findings depend on the same chemistry (Alturfan et al., 2009; Murphy et al., 2022).

Better oxidation markers would not in themselves mean better diabetes control, and glucose did not change significantly in the rats (Alturfan et al., 2009). The American Diabetes Association does not recommend routine antioxidant supplements such as vitamins E and C (American Diabetes Association, 2026).

A lower oxidation reading in a diabetic rat is a laboratory signal, not evidence that a snack can control blood sugar in people.

The authors themselves framed their animals as a model of moderate diabetes and called for longer studies; whether adding pistachios to a real diet improves blood-sugar control needs trials in people (Alturfan et al., 2009).

What Do Human Trials Show About Pistachios and Blood Sugar?

Human trials suggest that pistachios may lower fasting glucose slightly, with less consistent effects on longer-term control. A 2023 meta-analysis, with a search ending in June 2019, pooled eight trials in people at high cardiovascular risk (Hadi et al., 2023). It reported fasting glucose 5.32 mg/dL lower and fasting insulin 1.86 µIU/mL lower, but no significant change in HOMA-IR (Hadi et al., 2023).

A 2022 analysis of 17 trials in 940 adults found fasting glucose 3.62 mg/dL lower, with a small fall in systolic blood pressure (Baghery et al., 2022). A 2020 review of six trials reported improvements in fasting glucose but not in HbA1c or fasting insulin (Nowrouzi-Sohrabi et al., 2020). For scale, 5 mg/dL is under 0.3 mmol/L, far smaller than the gap between the diabetic and healthy rats in 2009 (Alturfan et al., 2009; Hadi et al., 2023).

Individual trials point in different directions

In Spain, 54 adults with prediabetes had lower fasting glucose, insulin and HOMA-IR after four months on a pistachio diet (Hernández-Alonso et al., 2014). In Iran, 48 people with type 2 diabetes saw HbA1c fall by 0.4 percentage points against a nut-free control (Parham et al., 2014). In a US feeding trial, 30 adults with well-controlled type 2 diabetes showed no change in fasting glucose or insulin after four weeks (Sauder et al., 2015).

Broader analyses of all nuts are more sobering. A 2019 meta-analysis of 40 trials with 2,832 participants found small falls in HOMA-IR and fasting insulin but no effect on fasting glucose or HbA1c (Tindall et al., 2019). The authors of the 2023 pistachio review add that few trials enrolled people with diabetes and most samples were small (Hadi et al., 2023).

Where Do Pistachios Fit in a Diabetes Diet?

Current guidelines treat nuts as one part of a healthy eating pattern, not as a diabetes treatment. The American Diabetes Association’s Standards of Care in Diabetes 2026 advise people with or at risk of diabetes to eat more plant protein, such as nuts, seeds and legumes, to reduce cardiovascular risk (American Diabetes Association, 2026). The same standards rate a Mediterranean-style pattern rich in fatty fish, nuts and seeds as lowering cardiovascular risk and improving glucose metabolism (American Diabetes Association, 2026).

Portion size matters because pistachios are energy-dense. Diabetes UK counts a small handful or one tablespoon of unsalted nuts or nut butter, 30 g, as a portion (Diabetes UK, n.d.). Raw pistachios provide 560 kcal per 100 g, so a 30 g portion supplies roughly 170 kcal, with about 6 g of protein and 3 g of fibre (U.S. Department of Agriculture, Agricultural Research Service, n.d.).

Most of the fat is unsaturated, and salt is the other catch: salted dry-roasted pistachios carry 428 mg of sodium per 100 g, about 128 mg in a 30 g portion, against 6 mg per 100 g for unsalted ones (U.S. Department of Agriculture, Agricultural Research Service, n.d.).

Nuts and the risk of developing type 2 diabetes

Evidence that eating nuts prevents type 2 diabetes is weak. A 2021 meta-analysis of observational studies found no association between total nut, peanut or tree nut intake and type 2 diabetes (Becerra-Tomás et al., 2021). Peanut butter was the one possible exception, with a modestly lower risk, and the certainty of the evidence was rated very low (Becerra-Tomás et al., 2021). Such studies show associations, not effects, so they cannot settle whether pistachios themselves change risk.

How Strong Is the Evidence?

The 2009 study on its own is weak evidence. It tested one dose in eight rats per group, used a model closer to type 1 than type 2 diabetes, relied on unspecific assays and contains internal inconsistencies (Alturfan et al., 2009; Furman, 2021; Murphy et al., 2022). Its only glucose result was not significant (Alturfan et al., 2009). Rat experiments like this one can point to a mechanism worth testing, but they cannot show a benefit for people (Alturfan et al., 2009; Furman, 2021).

Human evidence is better but still thin. Pistachio meta-analyses pool a handful of small, short trials, many in people without diabetes, and report small falls in fasting glucose (Hadi et al., 2023; Baghery et al., 2022), while the all-nut analysis found no effect on fasting glucose or HbA1c (Tindall et al., 2019). For these reasons the evidence on the article’s central question, whether pistachios improve blood-sugar control in people with diabetes, is rated limited.

Pistachios can still fit into a diabetes diet as an unsalted snack within the eating patterns that guidelines support (American Diabetes Association, 2026; Diabetes UK, n.d.). The evidence does not support the claim that they control diabetes by reducing glycation, which the 2009 study never measured (Alturfan et al., 2009).

Frequently asked questions

Do pistachios lower blood sugar?

Slightly, at best. Pooled human trials report fasting glucose about 3.6 to 5.3 mg/dL lower with pistachios, a small change, with no clear effect on HbA1c (Hadi et al., 2023; Nowrouzi-Sohrabi et al., 2020). In the 2009 rat study, glucose in pistachio-fed diabetic rats fell by about 9%, which the authors called insignificant (Alturfan et al., 2009).

Did the 2009 study test pistachios in people?

No. It used 32 Wistar rats in four groups of eight, and two of the groups were made diabetic with streptozotocin, a compound used mainly to model type 1 diabetes (Alturfan et al., 2009; Furman, 2021). Most people with diabetes have type 2, so the rat results cannot be read as a finding for patients (International Diabetes Federation, 2025).

What are TBARS and total antioxidant activity?

TBARS is a test meant to reflect oxidised fats, reported as malondialdehyde, while total antioxidant activity estimates how well a blood sample neutralises reactive molecules. A 2022 expert consensus advises against relying on either assay in clinical studies, partly because thiobarbituric acid reacts with many substances besides malondialdehyde (Murphy et al., 2022).

What counts as a portion of pistachios?

Diabetes UK counts a small handful or one tablespoon of unsalted nuts or nut butter, 30 g, as one portion (Diabetes UK, n.d.). Based on USDA data, 30 g of raw pistachios provides about 170 kcal, and salted dry-roasted pistachios add roughly 128 mg of sodium per portion (U.S. Department of Agriculture, Agricultural Research Service, n.d.).

Do nuts prevent type 2 diabetes?

The evidence is weak. A 2021 meta-analysis of observational studies found no clear link between eating nuts and the risk of type 2 diabetes, apart from a possible lower risk with peanut butter, and rated the certainty very low (Becerra-Tomás et al., 2021). Guidelines recommend nuts mainly for heart health (American Diabetes Association, 2026).

This article is for general information and is not medical advice. It was reviewed for accuracy by a qualified clinician; decisions about your health should be made with your own doctor.