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"

Two researchers (F.B and S.K.F.-P.) reviewed the abstracts and titles of all of the acknowledged research to determine whether it was eligible for inclusion in the present meta-analysis according to the inclusion criteria. The authors included all of the relevant available data from 17 articles on interventional studies. Regarding the objection raised about the effect size calculation, the inclusion of the various effect sizes from 1 study is a routine approach used in numerous meta-analyses, and their inclusion in the study did not impair the accuracy of the findings. The included studies were homogeneous in terms of intervention, outcomes, and participants, and the high rate of heterogeneity between the included studies for the majority of the study outcomes may have derived from the different characteristics of the participant populations, especially differences in their health status. As no study included in the review reported the correlation coefficient between the placebo conditions and the experimental conditions, the authors reanalyzed the data by inputting a moderate correlation coefficient of 0.5. Our study showed that pistachio consumption has a positive effect in terms of reducing the components of metabolic syndrome. In conclusion, this study reanalyzed the data and justified the methods used for showing the positive effect of pistachio consumption on metabolic syndrome components, and the potential for further research to identify the underlying mechanisms and the effects on various populations. The study's protocol was registered, and Comprehensive Meta-Analysis software was used in the statistical analyses. The authors recommend further research to investigate the potential effect of the consumption of pistachios. Systematic Review Registration: PROSPERO registration no. CRD42021285424.

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

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 (57 g/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 57 g/d of dry roasted unsalted pistachios (319 kcal; fat 26 g; 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. This trial was registered at clinicaltrials.gov as NCT04056208.

Can different types of tree nuts and peanuts induce varied effects on specific blood lipid parameters? A systematic review and network meta-analysis

Tree nuts and peanuts have shown cardioprotective effects through the modulation of blood lipid levels. Despite the abundance of scientific evidence available, it remains uncertain whether the type of nut consumed influences these changes. The objective of this study was to evaluate and rank the effects of six types of nuts on total cholesterol (total-c), low-density lipoprotein (LDL-c), triglyceride (TG) and high-density lipoprotein (HDL-c) levels through a systematic search of randomized controlled trials (RCTs), a frequentist network meta-analysis (NMA), and the estimation of SUCRA values. A total of 76 RCTs were ultimately analyzed. The total c for pistachios, almond, and walnuts; LDL-c for cashews, walnuts, and almond; and TG for hazelnuts and walnuts significantly decreased, while only peanuts exhibited a significant increase in HDL-c levels. According to the rankings, the most effective type of nut for reducing total cholesterol was pistachio, cashew for LDL-c, hazelnut for TG, and peanut for increasing HDL-c levels. It should be noted that every type of nut analyzed exhibited a significant positive impact on some parameters, and specific types demonstrated enhanced advantages for particular blood lipids. These results endorse the use of personalized nutritional strategies to address and prevent dyslipidemia.Registration: PROSPERO database CRD42021270779.

Nuts and seeds consumption and risk of cardiovascular disease, type 2 diabetes and their risk factors: a systematic review and meta-analysis

Objectives

We aimed to systematically review studies and evaluate the strength of the evidence on nuts/seeds consumption and cardiometabolic diseases and their risk factors among adults.

Methods

A protocol was pre-registered in PROSPERO (CRD42021270554). We searched MEDLINE, Embase, Cochrane Central Register of Controlled Trials and Scopus up to September 20, 2021 for prospective cohort studies and ≥12-week randomized controlled trials (RCTs). Main outcomes were cardiovascular disease (CVD), coronary heart disease (CHD), stroke and type 2 diabetes (T2D), secondary total-/low density lipoprotein (LDL)-cholesterol, blood pressure and glycaemic markers. Data extraction and risk of bias (RoB) assessments (using RoB 2.0 and RoB-NObS) were performed in duplicate. Effect sizes were pooled using random-effects meta-analyses and expressed as relative risk (RR) or weighted mean differences with 95% confidence intervals (CI); heterogeneity quantified as I ². One-stage dose-response analyses assessed the linear and non-linear associations with CVD, CHD, stroke and T2D. The strength of evidence was classified per the World Cancer Research Fund criteria.

Results

After screening 23,244 references, we included 42 papers from cohort studies (28 unique cohorts, 1,890,573 participants) and 18 RCTs (2,266 participants). In the cohorts, mainly populations with low consumption, high versus low total nuts/seeds consumption was inversely associated with total CVD (RR 0.81; 95% CI 0.75, 0.86; I ² = 67%), CVD mortality (0.77; 0.72, 0.82; I ² = 59.3%), CHD (0.82; 0.76, 0.89; I ² = 64%), CHD mortality (0.75; 0.65, 0.87; I ² = 66.9%) and non-fatal CHD (0.85; 0.75, 0.96; I ² = 62.2%). According to the non-linear dose-response analyses, consumption of 30 g/day of total nuts/seeds was associated with RRs of similar magnitude. For stroke and T2D the summary RR for high versus low intake was 0.91 (95% CI 0.85, 0.97; I ² = 24.8%) and 0.95 (0.75, 1.21; I ² = 82.2%). Intake of nuts (median ~50 g/day) lowered total (-0.15 mmol/L; -0.22, -0.08; I ² = 31.2%) and LDL-cholesterol (-0.13 mmol/L; -0.21, -0.05; I ² = 68.6%), but not blood pressure. Findings on fasting glucose, HbA1c and insulin resistance were conflicting. The results were robust to sensitivity and subgroup analyses. We rated the associations between nuts/seeds and both CVD and CHD as probable. There was limited but suggestive evidence for no association with stroke. No conclusion could be made for T2D.

Conclusion

There is a probable relationship between consumption of nuts/seeds and lower risk of CVD, mostly driven by CHD, possibly in part through effects on blood lipids. More research on stroke and T2D may affect the conclusions. The evidence of specific nuts should be further investigated.