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Research Area: Diabetes

Effect of premeal pistachio supplementation on cardiometabolic risk factors among Asian Indian adults with prediabetes: A randomized controlled trial.

Ashwini, K., K. Abirami, R. Gayathri, S. Sasikala, V. Sudha, S. Shobana, R.G. Jeevan, K. Krishnaswamy, V. Deepika, M. Rajalakshmi, R.M.R. Bai, K. Parkavi, S. Padmavathi, R.M. Anjana, R. Unnikrishnan, F.B. Hu, W.C. Willett, J. Salas-Salvadó, S.N. Bhupathiraju, V. Mohan, 2025. Effect of premeal pistachio supplementation on cardiometabolic risk factors among Asian Indian adults with prediabetes: A randomized controlled trial. J Nutr. 155(3):899-909. https://doi.org/10.1016/j.tjnut.2024.12.005

Background: Asian Indians are susceptible to developing type 2 diabetes at a lower age and often consume diets that are high in glycemic load and low in healthy fats. Objectives: This study aimed to evaluate the effect of 30g prebreakfast and 30g predinner supplementation of pistachios for 12 wk on glycated hemoglobin (HbA1c), other glycemic markers, anthropometry, and lipid profile of Asian Indians with prediabetes. Methods: In a 12-wk parallel arm, randomized controlled trial, we recruited 120 participants with prediabetes based on American Diabetes Association criteria. The intervention group (n = 60) consumed 60g pistachios (30g prebreakfast and predinner) whereas the control group (n = 60) followed a routine diet that excluded nuts. At baseline and 12 wk, we collected blood samples for biochemical analysis, anthropometrics, and 24-h recalls. Participants wore a continuous glucose monitoring (CGM) sensor during the trial’s first and last 2 wk. Urinary N-methyl-trans-4-hydroxy-l-proline (MHP) was measured as a marker of pistachio consumption. Results: A total of 109 participants completed the study (follow-up rate = 90.8%). Compared with participants in the control group, those in the intervention group had significant reductions in HbA1c (mean between-group difference: −0.2; 95% confidence interval: −0.3, −0.1; P < 0.001] with no significant changes in fasting or 2-h post glucose load plasma glucose. Compared with the control group, the intervention group had significant reductions in serum triglyceride, waist circumference, lipid accumulation product, visceral adiposity index, and atherogenic index. Urinary MHP (mg/g creatinine) showed a 62% increase in the intervention compared with the control group (P < 0.05). CGM data revealed significant decreases in the incremental area under the curve, 2-h after breakfast (28%, p=0.01) and after dinner (17%, P = 0.002) in the intervention group compared to the control group. Conclusions: A 12-wk, premeal load of 60g pistachios lowers HbA1c and improves cardiometabolic profile among Asian Indians with prediabetes. This is among the first studies to investigate these effects in this ethnic group.

Brazil nut consumption reduces DNA damage in overweight type 2 diabetes mellitus patients.

Macan, T.P., M.L. Magenis, A.P. Damiani, I.O. Monteiro, G.B. Silveira, R.P. Zaccaron, P.C.L. Silveira, J.P.F. Teixeira, G. Gajski, V.M. Andrade, 2024. Brazil nut consumption reduces DNA damage in overweight type 2 diabetes mellitus patients. Mutat Res Genet Toxicol Environ Mutagen. 895:503739. https://doi.org/10.1016/j.mrgentox.2024.503739

Type 2 diabetes mellitus (T2D) is a metabolic disease, which occurs largely due to unhealthy lifestyle. As oxidative stress is believed to promote T2D, by inducing damage to lipids, proteins, and DNA, appropriate dietary interventions seem critical to prevent, manage, and even reverse this condition. Brazil nuts (Bertholletia excelsa, H.B.K.) are nature’s richest source of selenium, a mineral that has shown several health benefits. Therefore, this study aims to assess the effects of selenium consumption, through Brazil nuts, on biochemical and oxidative stress parameters, and genomic instability in T2D patients. We recruited 133 patients with T2D, registered in the Integrated Clinics of the University of Southern Santa Catarina (Brazil). Participants consumed one Brazil nut a day for six months. Blood samples and exfoliated buccal cells were collected at the beginning and the end of the intervention. The glycemic profile, lipid profile, renal profile and hepatic profile, DNA damage and selenium content were evaluated. A total of 74 participants completed the intervention. Brazil nut consumption increased selenium and GSH levels, GPx, and CAT activity while DCF and nitrites levels decreased. Total thiols increased, and protein carbonyl and MDA levels decreased. Levels of baseline and oxidative DNA damage in T2D patients were significantly decreased, as well as the frequency of micronuclei and nuclear buds. The fasting glucose levels, HDL and LDL cholesterol, and GGT levels that increased significantly in patients with type 2 diabetes were significantly reduced with nut consumption. Our results show an increase in antioxidant activity, along with reductions of protein and lipid oxidation as well as DNA damage, suggesting that Brazil nut consumption could be an ally in reducing oxidative stress and modulating the genomic instability in T2D patients.

Intake of pistachios as a nighttime snack has similar effects on short- and longer-term glycemic control compared with education to consume 1-2 carbohydrate exchanges in adults with prediabetes: A 12-wk randomized crossover trial.

Riley, T.M., P.M. Kris-Etherton, T.L. Hart, K.S. Petersen, 2024. Intake of pistachios as a nighttime snack has similar effects on short- and longer-term glycemic control compared with education to consume 1-2 carbohydrate exchanges in adults with prediabetes: A 12-wk randomized crossover trial. J Nutr. 154(4):1219-1231. https://doi.org/10.1016/j.tjnut.2024.01.021

Background: Nut intake is associated with better glycemic control and lower cardiovascular disease (CVD) risk. It remains unclear if nut intake timing affects glycemic control and CVD risk factors. Intake of pistachios as a nighttime snack may attenuate morning glucose production and lower fasting plasma glucose (FPG). Objectives: We assessed the effects of a nighttime (after dinner and before bedtime) pistachio snack (57g/d) on glycemic control markers, vascular health, lipids/lipoproteins, and diet quality compared with education to consume 1–2 carbohydrate (CHO) exchanges (usual care) in individuals with prediabetes. Methods: A 2-period, randomized crossover trial was conducted. Participants were provided 57g/d of dry roasted unsalted pistachios (319 kcal; fat 26g; CHO 16 g; protein 12 g; fiber 6 g) as a nighttime snack or received usual care for 12 wk. Primary (FPG) and secondary outcomes [hemoglobin A1c (HbA1c), insulin, Homeostatic Model Assessment for Insulin Resistance (HOMA-IR), lipids/lipoproteins, vascular health, and Healthy Eating Index-2015 (HEI-2015)] were measured before and after each condition. Results: A total of 66 participants (50.9 ± 11.6 y, FPG: 106.2 ± 6.4 mg/dL) were randomly assigned, and 51 participants completed the trial. No between-condition differences in FPG {0.9 mg/dL [95% confidence interval (CI): −1.2, 3.1]}, HbA1c, insulin, HOMA-IR, lipids/ lipoproteins, blood pressure, or vascular health were observed. The HEI-2015 score was higher after the pistachio condition [6.8 points (95% CI: 1.5, 12.1)] than after usual care driven by higher component scores for seafood and plant proteins [2.0 points (95% CI: 1.0, 2.9)], refined grains [2.3 points (95% CI: 1.1, 3.5)], and the fatty acid ratio [1.7 points (95% CI: 0.0, 3.5)]. Conclusions: In adults with prediabetes, consuming 57 g/d of pistachios as a nighttime snack increased diet quality but had similar effects on glycemic markers, lipids/lipoproteins, blood pressure, and vascular health compared with the usual care comparator. Pistachios may be a healthful alternative to carbohydrate-rich nighttime snacks to increase alignment with Dietary Guidelines for Americans.

Mixed nut consumption improves brain insulin sensitivity: a randomized, single-blinded, controlled, crossover trial in older adults with overweight or obesity.

 Nijssen, K.M., R.P. Mensink, J. Plat, D. Ivanov, H. Preissl, P.J. Joris, 2024. Mixed nut consumption improves brain insulin sensitivity: a randomized, single-blinded, controlled, crossover trial in older adults with overweight or obesity. Am J Clin Nutr. 119(2):314-323. https://doi.org/10.1016/j.ajcnut.2023.12.010

Background: Improving brain insulin sensitivity, which can be assessed by measuring regional cerebral blood flow (CBF) responses to intranasal insulin, may prevent age-related metabolic and cognitive diseases. Objectives: This study aimed to investigate longer-term effects of mixed nuts on brain insulin sensitivity in older individuals with overweight/obesity. Methods: In a randomized, single-blinded, controlled, crossover trial, 28 healthy adults (mean ± standard deviation: 65 ± 3 years; body mass index: 27.9 ± 2.3 kg/m2) received either daily 60-g mixed nuts (15 g of walnuts, pistachio, cashew, and hazelnuts) or no nuts (control) for 16 weeks, separated by an 8-week washout period. Throughout the study, participants were instructed to adhere to the Dutch food-based dietary guidelines. During follow-up, brain insulin action was assessed by quantifying acute effects of intranasal insulin on regional CBF using arterial spin labeling magnetic resonance imaging. Furthermore, effects on peripheral insulin sensitivity (oral glucose tolerance test), intrahepatic lipids, and cardiometabolic risk markers were assessed. Results: Body weight and composition did not change. Compared with control, mixed nut consumption improved regional brain insulin action in 5 clusters located in the left (difference in CBF responses to intranasal insulin: -4.5 ± 4.7 mL/100 g/min; P < 0.001; -4.6 ± 4.8 mL/100 g/min; P < 0.001; and -4.3 ± 3.6 mL/100 g/min; P = 0.007) and right occipital lobes (-4.3 ± 5.6 mL/100 g/min; and -3.9 ± 4.9 mL/100 g/min; P = 0.028). A fifth cluster was part of the left frontal lobe (-5.0 ± 4.6 mL/100 g/min; P < 0.001). Peripheral insulin sensitivity was not affected. Intrahepatic lipid content (-0.7%-point; 95% CI: -1.3%-point to -0.1%-point; P = 0.027), serum low-density lipoprotein cholesterol concentration (-0.24 mmol/L; 95% CI: -0.44 to -0.04 mmol/L; P = 0.019), and systolic blood pressure (-5 mm Hg; 95% CI: -8 to -1 mm Hg; P = 0.006) were lower after the mixed nut intervention. Conclusions: Longer-term mixed nut consumption affected insulin action in brain regions involved in the modulation of metabolic and cognitive processes in older adults with overweight/obesity. Intrahepatic lipid content and different cardiometabolic risk markers also improved, but peripheral insulin sensitivity was not affected.