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Research Nut: Walnuts

Impact of γ-irradiation and thermal processing on the antigenicity of almond, cashew nut and walnut proteins.

Su, M., M. Venkatachalam, S.S. Teuber, K.H. Roux, S.K. Sathe, 2004. Impact of γ-irradiation and thermal processing on the antigenicity of almond, cashew nut and walnut proteins. J Sci Food Agric. 84:1119–1125.

Whole unprocessed almonds, cashew nuts and walnuts were each subjected to γ -irradiation (1, 5, 10 and 25 kGy) followed by heat processing including autoclaving (121°C, 15 psi for 15 and 30min), dry roasting (138 and 160°C for 30 min each, 168 and 177◦C for 12 min each), blanching (100°C for 5 and 10 min), oil roasting (191°C, 1min) and microwave heating (500W for 1 and 3min). Rabbit polyclonal antibodies were raised against each major protein isolated from defatted, but not subjected to γ -irradiation and/or any thermal processing, almond, cashew nut and walnut flours. Immunoreactivity of almond, cashew nut and walnut proteins soluble in borate saline buffer, normalised to 1mg protein ml−1 for all samples, was determined by inhibition enzyme-linked immunosorbent assay (ELISA) and Western blotting. ELISAs and Western blotting experiments indicated that almond, cashew nut and walnut proteins exposed to γ -irradiation alone or followed by various thermal treatments remained antigenically stable.

Lipophilic and hydrophilic antioxidant capacities of common foods in the United States

Wu, X., Beecher, G.R., Holden, J.M., Haytowitz, D.B., Gebhardt, S.E., R.L. Prior, 2004.  Lipophilic and hydrophilic antioxidant capacities of common foods in the United States. J Agric Food Chem. 52:4026-37.

Both lipophilic and hydrophilic antioxidant capacities were determined using the oxygen radical absorbance capacity (ORACFL) assay with fluorescein as the fluorescent probe and 2,2´-azobis(2-amidinopropane) dihydrochloride as a peroxyl radical generator on over 100 different kinds of foods, including fruits, vegetables, nuts, dried fruits, spices, cereals, infant, and other foods. Most of the foods were collected from four different regions and during two different seasons in U.S. markets. Total phenolics of each sample were also measured using the Folin-Ciocalteu reagent. Hydrophilic ORACFL values (H-ORACFL) ranged from 0.87 to 2641 μmol of Trolox equivalents (TE)/g among all of the foods, whereas lipophilic ORACFL values (L-ORACFL) ranged from 0.07 to 1611 μmol of TE/g. Generally, L-ORACFL values were <10% of the H-ORACFL values except for a very few samples. Total antioxidant capacity was calculated by combining L-ORACFL and H-ORACFL. Differences of ORACFL values in fruits and vegetables from different seasons and regions were relatively large for some foods but could not be analyzed in detail because of the sampling scheme. Two different processing methods, cooking and peeling, were used on selected foods to evaluate the impact of processing on ORACFL. The data demonstrated that processing can have significant effects on ORACFL. Considering all of the foods analyzed, the relationship between TP and H-ORACFL showed a very weak correlation. Total hydrophilic and lipophilic antioxidant capacity intakes were calculated to be 5558 and 166 μmol of TE/day, respectively, on the basis of data from the USDA Continuing Survey of Food Intakes by Individuals (1994-1996).

Concentrations of proanthocyanidins in common foods and estimations of normal consumption

Gu, L., M.A. Kelm, J.F. Hammerstone, G. Beecher, J. Holden, D. Haytowitz, S. Gebhardt, R.L. Prior, 2004.  Concentrations of proanthocyanidins in common foods and estimations of normal consumption. J Nutr. 134:613-17.

Proanthocyanidins (PAs) have been shown to have potential health benefits. However, no data exist concerning their dietary intake. Therefore, PAs in common and infant foods from the U.S. were analyzed. On the bases of our data and those from the USDA’s Continuing Survey of Food Intakes by Individuals (CSFII) of 1994-1996, the mean daily intake of PAs in the U.S. population (>2 y old) was estimated to be 57.7 mg/person. Monomers, dimers, trimers, and those above trimers contribute 7.1, 11.2, 7.8, and 73.9% of total PAs, respectively. The major sources of PAs in the American diet are apples (32.0%), followed by chocolate (17.9%) and grapes (17.8%). The 2- to 5-y-old age group (68.2 mg/person) and men >60 y old (70.8 mg/person) consume more PAs daily than other groups because they consume more fruit. The daily intake of PAs for 4- to 6-mo-old and 6- to 10-mo-old infants was estimated to be 1.3 mg and 26.9 mg, respectively, based on the recommendations of the American Academy of Pediatrics. This study supports the concept that PAs account for a major fraction of the total flavonoids ingested in Western diets.

Dietary α-linolenic acid reduced inflammatory and lipid cardiovascular risk factors in hypercholesterolemic men and women

Zhao, G., T.D. Etherton, K.R. Martin, S.G. West, P.J. Gillies, P.M. Kris-Etherton, 2004.  Dietary α-linolenic acid reduced inflammatory and lipid cardiovascular risk factors in hypercholesterolemic men and women. J. Nutr. 134:2991-97.

α-Linolenic acid (ALA) reduces cardiovascular disease (CVD) risk, possibly by favorably changing vascular inflammation and endothelial dysfunction. Inflammatory markers and lipids and lipoproteins were assessed in hypercholesterolemic subjects (n=23) fed 2 diets low in saturated fat and cholesterol, and high in PUFA varying in ALA (ALA Diet) and linoleic acid (LA Diet) compared with an average American diet (AAD). The ALA Diet provided 17% energy from PUFA (10.5% LA; 6.5% ALA); the LA Diet provided 16.4% energy from PUFA (12.6% LA; 3.6% ALA); and the AAD provided 8.7% energy from PUFA (7.7% LA; 0.8% ALA). The ALA Diet decreased C-reactive protein (CRP, P < 0.01), whereas the LA Diet tended to decrease CRP (P = 0.08). Although the 2 high-PUFA diets similarly decreased intercellular cell adhesion molecule-1 vs. AAD (-19.1% by the ALA Diet, P < 0.01; -11.0% by the LA Diet, P < 0.01), the ALA Diet decreased vascular cell adhesion molecule-1 (VCAM-1, -15.6% vs. -3.1%, P < 0.01) and E-selectin (-14.6% vs. -8.1%, P < 0.01) more than the LA Diet. Changes in CRP and VCAM-1 were inversely associated with changes in serum eicosapentaenoic acid (EPA) (r = -0.496, P = 0.016; r = -0.418, P = 0.047), or EPA plus docosapentaenoic acid (r = -0.409, P = 0.053; r = -0.357, P= 0.091) after subjects consumed the ALA Diet. The 2 high-PUFA diets decreased serum total cholesterol, LDL cholesterol and triglycerides similarly (P < 0.05); the ALA Diet decreased HDL cholesterol and apolipoprotein AI compared with the AAD (P < 0.05). ALA appears to decrease CVD risk by inhibiting vascular inflammation and endothelial activation beyond its lipid-lowering effects.

Including walnuts in a low-fat/modified-fat diet improves HDL cholesterol-to-total cholesterol ratios in patients with Type 2 diabetes

Tapsell, L.C., L.J. Gillen, C.S. Patch, M. Batterham, A. Owen, M. Baré, M. Kennedy, 2004. Including walnuts in a low-fat/modified-fat diet improves HDL cholesterol-to-total cholesterol ratios in patients with Type 2 diabetes. Diabetes Care. 27:2777-83.

Objective: The aim of this study was to examine the effect of a moderate-fat diet inclusive of walnuts on blood lipid profiles in patients with type 2 diabetes. Research Design and Methods: This was a parallel randomized controlled trial comparing three dietary advice groups each with 30% energy as fat: low fat, modified low fat, and modified low fat inclusive of 30 g of walnuts per day. Fifty-eight men and women, mean age 59.3 ± 8.1 years, started the trial. Dietary advice was given at baseline with monthly follow-up and fortnightly phone calls for support. Body weight, percent body fat, blood lipids, HbA1c, total antioxidant capacity, and erythrocyte fatty acid levels were measured at 0, 3, and 6 months. Data were assessed by repeated-measures ANOVA with an intention-to-treat model. Results: The walnut group achieved a significantly greater increase in HDL cholesterol-to-total cholesterol ratio (P = 0.049) and HDL (P = 0.046) than the two other treatment groups. A 10% reduction in LDL cholesterol was also achieved in the walnut group, reflecting a significant effect by group (P = 0.032) and time (P = 0.036). There were no significant differences between groups for changes in body weight, percent body fat, total antioxidant capacity, or HbA1c levels. The higher dietary polyunsaturated fat-to-saturated fat ratio and intakes of ω-3 fatty acids in the walnut group were confirmed by erythrocyte biomarkers of dietary intake. Conclusions: Structured “whole of diet” advice that included 30 g of walnuts/day delivering substantial amounts of polyunsaturated fatty acid improved the lipid profile of patients with type 2 diabetes.

A walnut diet improves endothelial function in hypercholesterolemic subjects

Ros, E., I. Núñez, A. Pérez-Heras, M. Serra, R. Gilabert, E. Casals, R. Deulofeu, 2004.  A walnut diet improves endothelial function in hypercholesterolemic subjects. Circulation. 109:1609-14.

Background: Epidemiological studies suggest that nut intake decreases coronary artery disease (CAD) risk. Nuts have a cholesterol-lowering effect that partly explains this benefit. Endothelial dysfunction is associated with CAD and its risk factors and is reversed by antioxidants and marine n-3 fatty acids. Walnuts are a rich source of both antioxidants and α-linolenic acid, a plant n-3 fatty acid. Methods and Results: To test the hypothesis that walnut intake will reverse endothelial dysfunction, we randomized in a crossover design 21 hypercholesterolemic men and women to a cholesterol-lowering Mediterranean diet and a diet of similar energy and fat content in which walnuts replaced ~32% of the energy from monounsaturated fat. Participants followed each diet for 4 weeks. After each intervention, we obtained fasting blood and performed ultrasound measurements of brachial artery vasomotor function. Eighteen subjects completing the protocol had suitable ultrasound studies. Compared with the Mediterranean diet, the walnut diet improved endothelium-dependent vasodilation and reduced levels of vascular cell adhesion molecule-1 (P<0.05 for both). Endothelium-independent vasodilation and levels of intercellular adhesion molecule-1, C-reactive protein, homocysteine, and oxidation biomarkers were similar after each diet. The walnut diet significantly reduced total cholesterol (-4.4±7.4%) and LDL cholesterol (-6.4±10.0%) (P<0.05 for both). Cholesterol reductions correlated with increases of both dietary α-linolenic acid and LDL γ-tocopherol content, and changes of endothelium-dependent vasodilation correlated with those of cholesterol to HDL ratios (P<0.05 for all). Conclusions: Substituting walnuts for monounsaturated fat in a Mediterranean diet improves endothelium-dependent vasodilation in hypercholesterolemic subjects. This finding might explain the cardioprotective effect of nut intake beyond cholesterol lowering.

Effect of a Mediterranean-style diet on endothelial dysfunction and markers of vascular inflammation in the metabolic syndrome

Esposito, K., R. Marfella, M. Ciotola, C. Di Palo, F. Giugliano, G. Giugliano, M. D’Armiento, F. D’Andrea, D. Giugliano, 2004.  Effect of a Mediterranean-style diet on endothelial dysfunction and markers of vascular inflammation in the metabolic syndrome. JAMA. 292:1440-6.

Context The metabolic syndrome has been identified as a target for dietary therapies to reduce risk of cardiovascular disease; however, the role of diet in the etiology of the metabolic syndrome is poorly understood. Objective To assess the effect of a Mediterranean-style diet on endothelial function and vascular inflammatory markers in patients with the metabolic syndrome. Design, Setting, and Patients Randomized, single-blind trial conducted from June 2001 to January 2004 at a university hospital in Italy among 180 patients (99 men and 81 women) with the metabolic syndrome, as defined by the Adult Treatment Panel III. Interventions Patients in the intervention group (n=90) were instructed to follow a Mediterranean-style diet and received detailed advice about how to increase daily consumption of whole grains, fruits, vegetables, nuts, and olive oil; patients in the control group (n=90) followed a prudent diet (carbohydrates, 50%-60%; proteins, 15%-20%; total fat, <30%). Main Outcome Measures Nutrient intake; endothelial function score as a measure of blood pressure and platelet aggregation response to L-arginine; lipid and glucose parameters; insulin sensitivity; and circulating levels of high-sensitivity C-reactive protein (hs-CRP) and interleukins 6 (IL-6), 7 (IL-7), and 18 (IL-18). Results After 2 years, patients following the Mediterranean-style diet consumed more foods rich in monounsaturated fat, polyunsaturated fat, and fiber and had a lower ratio of omega-6 to omega-3 fatty acids. Total fruit, vegetable, and nuts intake (274 g/d), whole grain intake (103 g/d), and olive oil consumption (8 g/d) were also significantly higher in the intervention group (P<.001). The level of physical activity increased in both groups by approximately 60%, without difference between groups (P=.22). Mean (SD) body weight decreased more in patients in the intervention group (−4.0 [1.1] kg) than in those in the control group (−1.2 [0.6] kg) (P<.001). Compared with patients consuming the control diet, patients consuming the intervention diet had significantly reduced serum concentrations of hs-CRP (P=.01), IL-6 (P=.04), IL-7 (P=0.4), and IL-18 (P=0.3), as well as decreased insulin resistance (P<.001). Endothelial function score improved in the intervention group (mean [SD] change, +1.9 [0.6]; P<.001) but remained stable in the control group (+0.2 [0.2]; P=.33). At 2 years of follow-up, 40 patients in the intervention group still had features of the metabolic syndrome, compared with 78 patients in the control group (P<.001). Conclusion A Mediterranean-style diet might be effective in reducing the prevalence of the metabolic syndrome and its associated cardiovascular risk.

Extensive in vitro cross-reactivity to seed storage proteins is present among walnut (Juglans) cultivars and species.

Comstock, S.S., G. McGranahan, W.R. Peterson, S.S. Teuber, 2004.  Extensive in vitro cross-reactivity to seed storage proteins is present among walnut (Juglans) cultivars and species. Clin Exp Allergy.34:1583-90.

BACKGROUND: Tree nuts, including English walnuts (Juglans regia), are sources of food allergens often associated with life-threatening allergic reactions. It is unknown if seed storage proteins from other Juglans species have IgE epitopes similar to those of the important English walnut allergens, Jug r 1 (2S albumin) and Jug r 2 (vicilin-like). OBJECTIVE: To screen for potential germplasm sources of hypoallergenic seed storage proteins of relevance in walnut food allergy. We sought to identify English walnut cultivars (cvs) or other Juglans species that showed decreased IgE binding to major seed storage proteins or an inability to cross-react with Jug r 1 or Jug r 2. METHODS: We determined if IgE in sera of patients who have had life-threatening systemic reactions to English walnut bound protein extracts from all tested walnut cvs (57 cvs total) or species (six) by Western immunoblot. Further, we used immunoblot inhibition to determine the in vitro cross-reactivity of Jug r 1 and Jug r 2, native and recombinant, with several walnut species. RESULTS: All walnut cvs and species contain allergenic proteins. Furthermore, as shown by in vitro immunoblot inhibition, the major walnut allergens in the species tested cross-reacted with those in J. regia cv. Chandler and J. nigra cv. Thomas extracts. CONCLUSIONS: Based on our findings, it is unlikely that a composite hypoallergenic walnut could be bred from available germplasm. In addition, patients with severe allergy to English walnut are likely to be clinically allergic to all commercial English walnut cvs and other closely related Juglans species.

Association of nut and seed intake with colorectal cancer risk in the European prospective investigation into cancer and nutrition.

Jenab, M., et al., 2004.  Association of nut and seed intake with colorectal cancer risk in the European prospective investigation into cancer and nutrition. Cancer Epidemiol Biomarkers Prev. 13(10):1595-603.

A link between unsaturated fatty acids or phytonutrients and reduced risk of colorectal cancer has been suggested. However, the effects of higher intake of dietary sources of these nutrients, such as the nuts and seeds food group, are less clear. The objective of this study was to determine the effects of nut and seed intake on colorectal cancer risk within the European Prospective Investigation into Cancer and Nutrition study, a large prospective cohort study involving 10European countries. Total nut and seed intake was determined from country-specific dietary questionnaires. The data set included 478,040 subjects (141,988 men, 336,052 women) with a total of 855 (327 men, 528 women) colon and 474 (215 men, 259 women) rectal cancer cases. A multivariate Cox proportional hazards model, stratified by center and controlled for fruit intake, dietary fiber, energy, height, weight, sex, age, physical activity, and smoking, was used. The data show no association between higher intake of nuts and seeds and risk of colorectal, colon, and rectal cancers in men and women combined, but a significant inverse association was observed in subgroup analyses for colon cancer in women at the highest (>6.2 g/d) versus the lowest (nonconsumers; hazard ratio, 0.69; 95% confidence interval, 0.50-0.95) category of intake and for the linear effect of log-transformed intake (hazard ratio, 0.89; 95% confidence interval, 0.80-0.98), with no associations in men. It is not evident from this data why there may be a stronger association in women or why it may be limited to the colon, suggesting that much further research is necessary.