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Research Nut: Walnuts

Cultural and historical aspects of Mediterranean nuts with emphasis on their attributed healthy and nutritional properties.

Salas-Salvadó J, Casas-Agustench P, Salas-Huetos A., 2011. Cultural and historical aspects of Mediterranean nuts with emphasis on their attributed healthy and nutritional properties. Nutr Metab Cardiovasc Dis. 21(Suppl 1):S1-6.

BACKGROUND AND AIMS: Nuts have been part of the human diet since prehistoric times. The aim of the present article is to describe the most important historical and cultural aspects of nut consumption throughout history. DATA SYNTHESIS: We discuss the following historical aspects of nuts originating in the Mediterranean: prehistory, the Egyptian civilization, their spread through the Mediterranean region by the Greek, Phoenician and Roman civilizations, and their reintroduction into Europe by means of the Al-Andalus culture. Particular emphasis is placed on the healthy and nutritional attributes that nuts have had throughout history. We also consider the role of the first globalization of food–the exchange of nuts between continents–and discuss the symbolism that nuts have had for humans throughout history in the context of cultural aspects of the Mediterranean region. CONCLUSIONS: Nuts and fruits are probably the earliest foods consumed by humans and are considered to be important because of their nutritional properties. Nuts have also been used in the past by different civilizations as drugs to prevent or treat several diseases.

Nut consumption and blood lipid levels: A pooled analysis of 25 intervention trials

Sabate´, J., K. Oda, E. Ros, 2010. Nut Consumption and Blood Lipid Levels A Pooled Analysis of 25 Intervention Trials. Arch Intern Med. 170(9):821-827.

Background: Epidemiological studies have consistently associated nut consumption with reduced risk for coronary heart disease. Subsequently, many dietary intervention trials investigated the effects of nut consumption on blood lipid levels. The objectives of this study were to estimate the effects of nut consumption on blood lipid levels and to examine whether different factors modify the effects. Methods: We pooled individual primary data from 25 nut consumption trials conducted in 7 countries among 583 men and women with normolipidemia and hypercholesterolemia who were not taking lipid-lowering medications. In a pooled analysis, we used mixed linear models to assess the effects of nut consumption and the potential interactions. Results: With a mean daily consumption of 67 g of nuts, the following estimated mean reductions were achieved: total cholesterol concentration (10.9 mg/dL [5.1% change]), low-density lipoprotein cholesterol concentration (LDL-C) (10.2 mg/dL [7.4% change]), ratio of LDL-C to high-density lipoprotein cholesterol concentration (HDL-C) (0.22 [8.3% change]), and ratio of total cholesterol concentration to HDL-C (0.24 [5.6% change]) (P<.001 for all) (to convert all cholesterol concentrations to millimoles per liter, multiply by 0.0259). Triglyceride levels were reduced by 20.6 mg/dL (10.2%) in subjects with blood triglyceride levels of at least 150 mg/dL (P<.05) but not in those with lower levels (to convert triglyceride level to millimoles per liter, multiply by 0.0113). The effects of nut consumption were dose related, and different types of nuts had similar effects on blood lipid levels. The effects of nut consumption were significantly modified by LDL-C, body mass index, and diet type: the lipid-lowering effects of nut consumption were greatest among subjects with high baseline LDL-C and with low body mass index and among those consuming Western diets. Conclusion: Nut consumption improves blood lipid levels in a dose-related manner, particularly among subjects with higher LDL-C or with lower BMI.

Long-term walnut supplementation without dietary advice induces favorable serum lipid changes in free-living individuals.

Torabian S., E. Haddad, Z. Cordero-MacIntyre, J. Tanzman, M.L. Fernandez, J. Sabate, 2010. Long-term walnut supplementation without dietary advice induces favorable serum lipid changes in free-living individuals. Eur J Clin Nutr. 64(3):274-9.

BACKGROUND/OBJECTIVES: Walnuts have been shown to reduce serum lipids in short-term well-controlled feeding trials. Little information exists on the effect and sustainability of walnut consumption for longer duration in a free-living situation. SUBJECTS/METHODS: A randomized crossover design in which 87 subjects with normal to moderate high plasma total cholesterol were initially assigned to a walnut-supplemented diet or habitual (control) diet for a 6-month period, then switched to the alternate dietary intervention for a second 6-month period. Each subject attended seven clinics 2 months apart. At each clinic, body weight was measured, and in five clinics (months 0, 4, 6, 10 and 12), a blood sample was collected. RESULTS: Our study showed that supplementing a habitual diet with walnuts (12% of total daily energy intake equivalent) improves the plasma lipid profile. This beneficial effect was more significant in subjects with high plasma total cholesterol at baseline. Significant changes in serum concentrations of total cholesterol (P=0.02) and triglycerides (P=0.03) were seen and nearly significant changes in low-density lipoprotein cholesterol (LDL-C) (P=0.06) were found. No significant change was detected in either high-density lipoprotein (HDL) cholesterol LDL to HDL ratio. CONCLUSIONS: Including walnuts as part of a habitual diet favorably altered the plasma lipid profile. The lipid-lowering effects of walnuts were more evident among subjects with higher lipid baseline values, precisely those people with greater need of reducing plasma total and LDL-C.

Cross-sectional association of nut intake with adiposity in a Mediterranean population.

Casas-Agustench P., M. Bulló, E. Ros, J. Basora, J. Salas-Salvadó; on behalf of the Nureta-PREDIMED investigators, 2011. Cross-sectional association of nut intake with adiposity in a Mediterranean population. Nutr Metab Cardiovasc Dis. 21(7):518-525.

BACKGROUND AND AIMS: Nut intake has been inversely related to body mass index (BMI) in prospective studies. We examined dietary determinants of adiposity in an elderly Mediterranean population with customarily high nut consumption. METHODS AND RESULTS: A cross-sectional study was conducted in 847 subjects (56% women, mean age 67 years, BMI 29.7kg/m(2)) at high cardiovascular risk recruited into the PREDIMED study. Food consumption was evaluated by a validated semi-quantitative questionnaire, energy expenditure in physical activity by the Minnesota Leisure Time Activity questionnaire, and anthropometric variables by standard measurements. Nut intake decreased across quintiles of both BMI and waist circumference (P-trend <0.005; both). Alcohol ingestion was inversely related to BMI (P-trend=0.020) and directly to waist (P-trend=0.011), while meat intake was directly associated with waist circumference (P-trend=0.018). In fully adjusted multivariable models, independent dietary associations of BMI were the intake of nuts inversely (P=0.002) and that of meat and meat products directly (P=0.042). For waist circumference, independent dietary associations were intake of nuts (P=0.002) and vegetables (P=0.040), both inversely, and intake of meat and meat products directly (P=0.009). From the regression coefficients, it was predicted that BMI and waist circumference decreased by 0.78kg/m(2) and 2.1cm, respectively, for each serving of 30g of nuts. Results were similar in men and women. CONCLUSION:  Nut consumption was inversely associated with adiposity independently of other lifestyle variables. It remains to be explored whether residual confounding related to a healthier lifestyle of nut eaters might in part explain these results.

Identification of the 100 richest dietary sources of polyphenols: an application of the Phenol-Explorer database.

Pérez-Jiménez, J., V. Neveu, F. Vos, A. Scalbert, 2010. Identification of the 100 richest dietary sources of polyphenols: an application of the Phenol-Explorer database. European Journal of Clinical Nutrition. 64: S112–S120.

Background/Objectives: The diversity of the chemical structures of dietary polyphenols makes it difficult to estimate their total content in foods, and also to understand the role of polyphenols in health and the prevention of diseases. Global redox colorimetric assays have commonly been used to estimate the total polyphenol content in foods. However, these assays lack specificity. Contents of individual polyphenols have been determined by chromatography. These data, scattered in several hundred publications, have been compiled in the Phenol-Explorer database. The aim of this paper is to identify the 100 richest dietary sources of polyphenols using this database. Subjects/Methods: Advanced queries in the Phenol-Explorer database (www.phenol-explorer.eu) allowed retrieval of information on the content of 502 polyphenol glycosides, esters and aglycones in 452 foods. Total polyphenol content was calculated as the sum of the contents of all individual polyphenols. These content values were compared with the content of antioxidants estimated using the Folin assay method in the same foods. These values were also extracted from the same database. Amounts per serving were calculated using common serving sizes. Results: A list of the 100 richest dietary sources of polyphenols was produced, with contents varying from 15 000mg per 100g in cloves to 10mg per 100 ml in rose´ wine. The richest sources were various spices and dried herbs, cocoa products, some darkly coloured berries, some seeds (flaxseed) and nuts (chestnut, hazelnut) and some vegetables, including olive and globe artichoke heads. A list of the 89 foods and beverages providing more than 1mg of total polyphenols per serving was established. A comparison of total polyphenol contents with antioxidant contents, as determined by the Folin assay, also showed that Folin values systematically exceed the total polyphenol content values. Conclusions: The comprehensive Phenol-Explorer data were used for the first time to identify the richest dietary sources of polyphenols and the foods contributing most significantly to polyphenol intake as inferred from their content per serving.

A 3-year Mediterranean-style dietary intervention may modulate the association between adiponectin gene variants and body weight change.

Razquin, C., J.A. Martínez, M.A. Martínez-González, J. Salas-Salvadó, R. Estruch, A. Marti, 2010. A 3-year Mediterranean-style dietary intervention may modulate the association between adiponectin gene variants and body weight change. Eur J Nutr. 49(5):311-9.

Purpose Adiponectin gene variations have been associated with obesity. There are few interventional studies analyzing this association. The aim of this study was to analyze the effects of a nutritional intervention with Mediterranean-style diet and three (-4034A/C, +45T/G, and +276 G/T) adiponectin gene variants on 3-year body weight changes in high cardiovascular risk patients. Subjects and methods A total of 737 participants, aged 55–80 at high cardiovascular risk were assigned to a low-fat diet or to a Mediterranean-style diet (MD) groups, one with high intake of virgin olive oil (VOO) and the other with high intake of nuts. Anthropometric parameters were taken at baseline and after 3-year follow-up, and the genotyping of the -4034A/C, +45T/G, and +276 G/T polymorphisms was done. Results GG genotype of the +45T/G polymorphism was associated with 3-year higher body weight gain (B = 1.399; B = 0.043). TT genotype of the +276G/T polymorphism was linked to the highest 3-year body weight gain in men. Both Mediterranean diets appeared to reverse this effect (p for interaction = 0.053). Conclusion Adiponectin gene variation appeared to be associated with 3-year body weight changes in a high cardiovascular risk population. This association may be modulated by a nutritional intervention with a Mediterranean-style diet.

Effects of walnut consumption on endothelial function in type 2 diabetics: a randomized, controlled, cross-over trial.

Ma, Y., V.Y. Njike, J. Millet, S. Dutta, K. Doughty, J.A. Treu, D.L. Katz, 2010. Effects of walnut consumption on endothelial function in type 2 diabetics: a randomized, controlled, cross-over trial. Diabetes Care. 33(2):227-32.

Objective: To determine the effects of daily walnut consumption on endothelial function, cardiovascular biomarkers, and anthropometric measures in type 2 diabetics. Methods: This study was a randomized, controlled, single-blind, cross-over trial. Twenty-four participants with type 2 diabetes (mean age 58 years; 14 women, 10 men) were randomly assigned to one of the two possible sequence permutations to receive an ad libitum diet enriched with 56 g (366 kcal) of walnuts per day and an ad libitum diet without walnuts for 8 weeks. Subjects underwent endothelial function testing (measured as flow-mediated dilatation or FMD) and assessment of cardiovascular biomarkers before and after each 8-week treatment phase. The primary outcome measure was the change in FMD after 8 weeks. Secondary outcome measures included changes in plasma lipids, HbA1c, fasting glucose, insulin sensitivity, and anthropometric measures. Results: Endothelial function significantly improved after consumption of a walnut-enriched ad libitum diet compared to an ad libitum diet without walnuts (2.2 ± 1.7 % vs. 1.2 ± 1.6 %; p=0.04). The walnut-enriched diet increased fasting serum glucose, lowered serum total cholesterol and low-density lipoprotein cholesterol from baseline (10.0 ± 20.5 mg/dL; p=0.04, -9.7 ± 14.5 mg/dL; p<0.01; and -7.7 ± 10 mg/dL; p<0.01 respectively), though these changes were not significant when compared to an ad libitum diet without walnuts. There were no significant changes in anthropometric measures, plasma HbA1c, and insulin sensitivity. Conclusions: A walnut-enriched ad libitum diet improves endothelium-dependent vasodilatation in type 2 diabetics, suggesting a potential reduction in overall cardiac ris

Effect of whole walnuts and walnut-skin extracts on oxidant status in mice.

Bulló, M., M.R. Nogués, P. López-Uriarte, J. Salas-Salvadó, M. Romeu, 2010. Effect of whole walnuts and walnut-skin extracts on oxidant status in mice. Nutrition. 26(7-8):823-8.

Objective: To evaluate the effect of the intake of whole walnuts and walnut fractions on the oxidant status in mice. Methods: Thirty-six C57BL/6J male mice were randomized to be fed one of three diets: 1) a standard diet (control group), 2) a standard diet with 10% of whole walnuts (walnut-diet group), or 3) a standard diet with 2% of walnut skins (walnut-skin-diet group) for 8 wk. The plasma antioxidant capacity was measured by oxygen radical-absorbance capacity and plasma ferric-reducing antioxidant potential. Conjugated diene formation and reduced glutathione levels were also analyzed. Results: We observed no changes in plasma oxidation capability between the walnut and walnut skin groups with the exception of conjugated dienes. Plasma total antioxidant capacity and the ratio between reduced and oxidized forms of glutathione were lower in the walnut and walnut skin groups than in the control group. Conclusion: The decrease in the antioxidant burden observed in enzymatic and non-enzymatic antioxidant systems after sustained consumption of a whole-walnut or a walnut-skin diet in mice may be related to the plasma oxidation capability being maintained in the groups consuming the walnut diets.

Walnut extract inhibits LPS-induced activation of Bv-2 microglia via internalization of TLR4: possible involvement of phospholipase D2.

Willis, L.M., D.F. Bielinski, D.R. Fisher, N.R. Matthan, J.A. Joseph, 2010. Walnut extract inhibits LPS-induced activation of Bv-2 microglia via internalization of TLR4: possible involvement of phospholipase D2. Inflammation DOI: 10.1007/s10753-010-9189-0.

Walnuts are a rich source of essential fatty acids, including the polyunsaturated fatty acids alpha-linolenic acid and linoleic acid. Essential fatty acids have been shown to modulate a number of cellular processes in the brain, including the activation state of microglia. Microglial activation can result in the generation of cytotoxic intermediates and is associated with a variety of age-related and neurodegenerative conditions. In vitro, microglial activation can be induced with the bacterial cell wall component lipopolysaccharide (LPS). In the present study, we generated a methanolic extract of English walnuts (Juglans regia) and examined the effects of walnut extract exposure on LPS-induced activation in BV-2 microglial cells. When cells were treated with walnut extract prior to LPS stimulation, production of nitric oxide and expression of inducible nitric oxide synthase were attenuated. Walnut extract also induced a decrease in tumor necrosis-alpha (TNFα) production. We further found that walnut extract induced internalization of the LPS receptor, toll-like receptor 4, and that the anti-inflammatory effects of walnut were dependent on functional activation of phospholipase D2. These studies represent the first to describe the anti-inflammatory effects of walnuts in microglia, which could lead to nutritional interventions in the prevention and treatment of neurodegeneration.

Lifestyle counseling and supplementation with flaxseed or walnuts influence the management of metabolic syndrome.

Wu, H., A. Pan, Z. Yu, Q. Qi, L. Lu, G. Zhang, D. Yu, G. Zong, Y. Zhou, X. Chen, L. Tang, Y. Feng, H. Zhou, X. Chen, H. Li,W. Demark-Wahnefried, F.B. Hu, X. Lin, 2010. Lifestyle counseling and supplementation with flaxseed or walnuts influence the management of metabolic syndrome. J. Nutr. 140(11):1937-42. .

A healthy lifestyle may ameliorate metabolic syndrome (MetS); however, it remains unclear if incorporating nuts or seeds into lifestyle counseling (LC) has additional benefit. A 3-arm, randomized, controlled trial was conducted among 283 participants screened for MetS using the updated National Cholesterol Education Program Adult Treatment Panel III criteria for Asian Americans. Participants were assigned to a LC on the AHA guidelines, LC + flaxseed (30 g/d) (LCF), or LC + walnuts (30 g/d) (LCW) group. After the 12-wk intervention, the prevalence of MetS decreased significantly in all groups: -16.9% (LC), -20.2% (LCF), and -16.0% (LCW). The reversion rate of MetS, i.e. those no longer meeting the MetS criteria at 12 wk, was not significantly different among groups (LC group, 21.1%; LCF group, 26.6%; and LCW group, 25.5%). However, the reversion rate of central obesity was higher in the LCF (19.2%; P = 0.008) and LCW (16.0%; P = 0.04) groups than in the LC group (6.3%). Most of the metabolic variables (weight, waist circumference, serum glucose, total cholesterol, LDL cholesterol, apolipoprotein (Apo) B, ApoE, and blood pressure) were significantly reduced from baseline in all 3 groups. However, the severity of MetS, presented as the mean count of MetS components, was significantly reduced in the LCW group compared with the LC group among participants with confirmed MetS at baseline (P = 0.045). Our results suggest that a low-intensity lifestyle education program is effective in MetS management. Flaxseed and walnut supplementation may ameliorate central obesity. Further studies with larger sample sizes and of longer duration are needed to examine the role of these foods in the prevention and management of MetS.