Liu, W., E. Li, M. Hu, 2024. Efficacy of walnut supplementation in managing overweight and obesity: A meta-analysis of randomized clinical trials. J. Funct. Foods. Volume 122, 106515. https://doi.org/10.1016/j.jff.2024.106515.
This study aimed to assess how effective walnut supplementation is in managing overweight and obesity. A thorough search of PubMed, Embase, and Cochrane Central Register of Controlled Trials was carried out until March 2024. Two reviewers independently examined the suitability of studies and assessed the quality of reporting in the randomized controlled trials (RCTs) that were included. The results indicated that adding walnuts to the diet significantly lowered total cholesterol (TC) levels (p < 0.0001) and low-density lipoprotein-cholesterol (LDL-C) levels (p < 0.001). However, there was no notable difference in weight loss (p > 0.05) and body mass index (BMI) (p > 0.05) between those who received walnut supplementation and the control groups. Based on the RCT data, it appears that walnut supplementation can effectively decrease TC and LDL-C levels. Additionally, it seems to be a safe choice for individuals who are overweight or obese, as it did not have an adverse effect on body weight.
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.
Nijssen, K.M.R., M.A. Chavez-Alfaro, P.J. Joris, J. Plat, R.P. Mensink, 2024. Effects of longer-term mixed nut consumption on lipoprotein particle concentrations in older adults with overweight or obesity. Nutrients. 17(1):8. https://doi.org/10.3390/nu17010008
Background: Recently, we reported that longer-term mixed nut intake significantly reduced serum total and low-density lipoprotein (LDL)-cholesterol, but these markers may not fully capture lipoprotein-related cardiovascular disease (CVD) risk. Objectives: This randomized, controlled, single-blinded, crossover trial in older adults with overweight or obesity examined the effects of longer-term mixed nut consumption on lipoprotein particle size, number, and lipid distribution. Methods: Twenty-eight participants (aged 65 ±3years; BMI 27.9 ± 2.3 kg/m2) completed two 16-week periods (control [no nuts] vs. mixed nuts (60 g/day: 15g of walnuts, pistachios, cashews, and hazelnuts), separated by an 8-week washout. Plasma lipoprotein particle numbers, sizes, and lipid distributions across subclasses were analyzed using high-throughput nuclear magnetic resonance (NMR) spectroscopy. Results: Mixed nut consumption significantly reduced Apolipoprotein B (ApoB) concentrations (−0.07 g/L; p = 0.009), total cholesterol (−0.27 mmol/L; p = 0.047), non-HDL cholesterol (−0.28 mmol/L; p = 0.022), and total triacylglycerol (TAG) (−0.27 mmol/L; p = 0.008). Total very large-density lipoprotein (VLDL) particle numbers decreased by 24 nmol/L (p < 0.001), with reductions observed across all VLDL subclasses. Total LDL particle numbers (p = 0.044), specifically intermediate-density lipoprotein (IDL) (p = 0.002) and large LDL particles (p = 0.015), were also reduced, while HDL particle numbers and sizes were unaffected. The mixed nut intervention significantly reduced cholesterol concentrations across all VLDL subclasses and IDL (all p < 0.01), with no changes in LDL or HDL subclasses. TAG concentrations showed reductions across all lipoprotein subclasses (all p < 0.05). Conclusions: Longer-term mixed nut consumption may lower CVD risk in older adults and favorable shifts in ApoB-containing lipoprotein subclasses towards a less atherogenic profile.
Sumislawski, K., A. Widmer, R.R. Suro, M.E. Robles, K. Lillegard, D. Olson, J.R. Koethe, H.J. Silver, 2023. Consumption of tree nuts as snacks reduces metabolic syndrome risk in young adults: a randomized trial. Nutrients. 15(24):5051. doi: 10.3390/nu15245051.
Metabolic syndrome (MetSx) and its chronic disease consequences are major public health concerns worldwide. Between-meal snacking may be a modifiable risk factor. We hypothesized that consuming tree nuts as snacks, versus typical carbohydrate snacks, would reduce risk for MetSx in young adults. A prospective, randomized, 16-week parallel-group diet intervention trial was conducted in 84 adults aged 22-36 with BMI 24.5 to 34.9 kg/m2 and ≥1 MetSx clinical risk factor. Tree nuts snacks (TNsnack) were matched to carbohydrate snacks (CHOsnack) for energy (kcal), protein, fiber, and sodium content as part of a 7-day eucaloric menu. Difference in change between groups was tested by analysis of covariance using general linear models. Multivariable linear regression modeling assessed main effects of TNsnack treatment and interactions between TNsnack and sex on MetSx score. Age, BMI, and year of study enrollment were included variables. There was a main effect of TNsnack on reducing waist circumference in females (mean difference: -2.20 ± 0.73 cm, p = 0.004) and a trend toward reduced visceral fat (-5.27 ± 13.05 cm2, p = 0.06). TNsnack decreased blood insulin levels in males (-1.14 ± 1.41 mIU/L, p = 0.05) and multivariable modeling showed a main effect of TNsnack on insulin. Main effects of TNsnack on triglycerides and TG/HDL ratio were observed (p = 0.04 for both) with TG/HDL ratio reduced ~11%. A main effect of TNsnack (p = 0.04) and an interaction effect between TNsnack and sex (p < 0.001) on total MetSx score yielded 67% reduced MetSx score in TNsnack females and 42% reduced MetSx score in TNsnack males. To our knowledge, this is the first randomized parallel-arm study to investigate cardiometabolic responses to TNsnacks versus typical CHOsnacks among young adults at risk of MetSx. Our study suggests daily tree nut consumption reduces MetSx risk by improving waist circumference, lipid biomarkers, and/or insulin sensitivity-without requiring caloric restriction.
