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Research Nut: Walnuts

Edible nuts for memory.

Arslan, J., A.-U.-H. Gilani, H. Jamshed, S.F. Khan, M.A. Kamal, 2020. Edible nuts for memory. Curr Pharm Des. 26(37):4712-4720.

Nuts hold prime significance throughout the world as they offer multiple health benefits owing to their highly nutritious profile. A number of scientific studies have demonstrated their actions against inflammation, oxidative damage, the aging process, as well as dementia or memory loss. However, only walnuts, followed by almonds, hazelnuts and pistachios, have shown promising results in empirical studies for memory improvements. So, the current review focuses on presenting hypotheses regarding anti-dementia property of nine different nuts: almond, walnut, pistachio, Brazil nut, peanut, pecans, cashew, hazelnut, and chestnut. The nutritious profile of nuts contains essential fats (mostly mono- and poly-unsaturated fatty acids), proteins (source for arginine, lysine and tryptophan), vitamins (riboflavin, folate, and various tocopherols), fibers, minerals (calcium, sodium, magnesium, phosphorus and potassium) and trace elements (copper, zinc, and selenium). Interestingly, the constituents of natural products, nuts being an excellent example, work synergistically and/or in a side-effect neutralizing manner. These latter properties can make nuts an alternate therapy for humankind to fight against memory loss.

Clinical and molecular characterization of walnut and pecan allergy (NUT CRACKER Study).

Elizur, A., M.Y. Appel, L. Nachshon, M.B. Levy, N. Epstein-Rigbi, B. Pontoppidan, J. Lidholm, M.R. Goldberg, 2020. Clinical and molecular characterization of walnut and pecan allergy (NUT CRACKER Study). J Allergy Clin Immunol: In Practice. 8(1):157-165.e2

Background: Diagnostic methods for distinguishing walnut-allergic patients from walnut-sensitized but walnut-tolerant individuals are limited. Furthermore, characteristics of single walnut versus dual walnut-pecan allergy are lacking. Objective: To provide clinical and molecular characteristics of walnut- and pecan-allergic patients. Methods: A prospective cohort study of 76 walnut-sensitized patients was performed. Walnut skin prick test and serum measurements of specific IgE to walnut and its components were performed. Patients were challenged to walnut and pecan unless they regularly consumed walnut and pecan. Results: Of the 76 patients studied, 61 were diagnosed as walnut-allergic and 15 as walnut-tolerant. IgE levels greater than or equal to 0.35 kUA/L to Jug r 1 or 4 provided the best diagnostic method for identifying walnut-allergic patients (accuracy, 0.93). Of the 61 walnut-allergic patients, 49 were pecan-allergic whereas 12 were pecan-tolerant. None of the walnut-tolerant patients was allergic to pecan. Dual allergic patients had significantly lower walnut reaction dose (median, 100 mg vs 1230 mg; P < .001). IgE levels greater than or equal to 0.35 kUA/L to Jug r 4, low-molecular-weight vicilins, or high-molecular-weight vicilins best segregated dual walnut-pecan–allergic patients from single walnut-allergic patients. Inhibition studies demonstrated that walnut pretreatment completely blocked IgE binding to pecan, whereas in some patients, pecan incubation only partially blocked IgE binding to walnut. Conclusions: Walnut components are helpful in diagnosing walnut allergy and in identifying patients with pecan coallergy. Competitive ELISA indicates that pecan comprises a subset of the allergenic determinants of walnut.

The effect of green Mediterranean diet on cardiometabolic risk; a randomised controlled trial.

Tsaban, G., A. Yaskolka Meir, E. Rinott, H. Zelicha, A. Kaplan, A. Shalev, A. Katz, A. Rudich, A. Tirosh, I. Shelef, I. Youngster, S. Lebovitz,  N. Israeli, M. Shabat, D. Brikner, E. Pupkin, M. Stumvoll, J. Thiery, U. Ceglarek, J.T. Heiker, A. Körner, K. Landgraf, M. von Bergen, M. Blüher, M.J. Stampfer, I. Shai, 2020. The effect of green Mediterranean diet on cardiometabolic risk; a randomised controlled trial. Heart. heartjnl-2020-317802.  doi: 10.1136/heartjnl-2020-317802.

Background: A Mediterranean diet is favourable for cardiometabolic risk. Objective To examine the residual effect of a green Mediterranean diet, further enriched with green plant-based foods and lower meat intake, on cardiometabolic risk. Methods:  For the DIRECT-PLUS parallel, randomised clinical trial we assigned individuals with abdominal obesity/dyslipidaemia 1:1:1 into three diet groups: healthy dietary guidance (HDG), Mediterranean and green Mediterranean diet, all combined with physical activity. The Mediterranean diets were equally energy restricted and included 28 g/day walnuts. The green Mediterranean diet further included green tea (3–4 cups/day) and a Wolffia globosa (Mankai strain; 100 g/day frozen cubes) plant-based protein shake, which partially substituted animal protein. We examined the effect of the 6-month dietary induction weight loss phase on cardiometabolic state. Results Participants (n=294; age 51 years; body mass index 31.3 kg/m2; waist circumference 109.7 cm; 88% men; 10-year Framingham risk score 4.7%) had a 6-month retention rate of 98.3%. Both Mediterranean diets achieved similar weight loss ((green Mediterranean −6.2 kg; Mediterranean −5.4 kg) vs the HDG group −1.5 kg; p<0.001), but the green Mediterranean group had a greater reduction in waist circumference (−8.6 cm) than the Mediterranean (−6.8 cm; p=0.033) and HDG (−4.3 cm; p<0.001) groups. Stratification by gender showed that these differences were significant only among men. Within 6 months the green Mediterranean group achieved greater decrease in low-density lipoprotein cholesterol (LDL-C; green Mediterranean −6.1 mg/dL (−3.7%), −2.3 (-0.8%), HDG −0.2 mg/dL (+1.8%); p=0.012 between extreme groups), diastolic blood pressure (green Mediterranean −7.2 mm Hg, Mediterranean −5.2 mm Hg, HDG −3.4 mm Hg; p=0.005 between extreme groups), and homeostatic model assessment for insulin resistance (green Mediterranean −0.77, Mediterranean −0.46, HDG −0.27; p=0.020 between extreme groups). The LDL-C/high-density lipoprotein cholesterol (HDL-C) ratio decline was greater in the green Mediterranean group (−0.38) than in the Mediterranean (−0.21; p=0.021) and HDG (−0.14; p<0.001) groups. High-sensitivity C-reactive protein reduction was greater in the green Mediterranean group (−0.52 mg/L) than in the Mediterranean (−0.24 mg/L; p=0.023) and HDG (−0.15 mg/L; p=0.044) groups. The green Mediterranean group achieved a better improvement (−3.7% absolute risk reduction) in the 10-year Framingham Risk Score (Mediterranean−2.3%; p=0.073, HDG−1.4%; p<0.001). Conclusions: The green MED diet, supplemented with walnuts, green tea and Mankai and lower in meat/poultry, may amplify the beneficial cardiometabolic effects of Mediterranean diet.

Walnuts and vegetable oils containing oleic acid differentially affect the gut microbiota and associations with cardiovascular risk factors: Follow-up of a randomized, controlled, feeding trial in adults at risk for cardiovascular disease.

Tindall, A.M., C.J. McLimans, K.S. Petersen, P.M. Kris-Etherton, R. Lamendella, 2020.  Walnuts and vegetable oils containing oleic acid differentially affect the gut microbiota and associations with cardiovascular risk factors: Follow-up of a randomized, controlled, feeding trial in adults at risk for cardiovascular disease. J Nutr. 150(4):806-817.

Background: It is unclear whether the favorable effects of walnuts on the gut microbiota are attributable to the fatty acids, including α-linolenic acid (ALA), and/or the bioactive compounds and fiber. Objective: This study examined between-diet gut bacterial differences in individuals at increased cardiovascular risk following diets that replace SFAs with walnuts or vegetable oils. Methods: Forty-two adults at cardiovascular risk were included in a randomized, crossover, controlled-feeding trial that provided a 2-wk standard Western diet (SWD) run-in and three 6-wk isocaloric study diets: a diet containing whole walnuts (WD; 57-99 g/d walnuts; 2.7% ALA), a fatty acid-matched diet devoid of walnuts (walnut fatty acid-matched diet; WFMD; 2.6% ALA), and a diet replacing ALA with oleic acid without walnuts (oleic acid replaces ALA diet; ORAD; 0.4% ALA). Fecal samples were collected following the run-in and study diets to assess gut microbiota with 16S rRNA sequencing and Qiime2 for amplicon sequence variant picking. RESULTS: Subjects had elevated BMI (30 ± 1 kg/m2), blood pressure (121 ± 2/77 ± 1 mmHg), and LDL cholesterol (120 ± 5 mg/dL). Following the WD, Roseburia [relative abundance (RA) = 4.2%, linear discriminant analysis (LDA) = 4], Eubacterium eligensgroup (RA = 1.4%, LDA = 4), LachnospiraceaeUCG001 (RA = 1.2%, LDA = 3.2), Lachnospiraceae UCG004 (RA = 1.0%, LDA = 3), and Leuconostocaceae (RA = 0.03%, LDA = 2.8) were most abundant relative to taxa in the SWD (P ≤ 0.05 for all). The WD was also enriched in Gordonibacter relative to the WFMD. Roseburia (3.6%, LDA = 4) and Eubacterium eligensgroup (RA = 1.5%, LDA = 3.4) were abundant following the WFMD, and Clostridialesvadin BB60group (RA = 0.3%, LDA = 2) and gutmetagenome (RA = 0.2%, LDA = 2) were most abundant following the ORAD relative to the SWD (P ≤ 0.05 for all). Lachnospiraceae were inversely correlated with blood pressure and lipid/lipoprotein measurements following the WD. Conclusions: The results indicate similar enrichment of Roseburia following the WD and WFMD, which could be explained by the fatty acid composition. Gordonibacter enrichment and the inverse association between Lachnospiraceae and cardiovascular risk factors following the WD suggest that the gut microbiota may contribute to the health benefits of walnut consumption in adults at cardiovascular risk. This trial was registered at clinicaltrials.gov as NCT02210767.