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Research Nut: Walnuts

Favourable nutrient intake and displacement with long-term walnut supplementation among elderly: Results of a randomised trial.

Bitok, E., K. Jaceldo-Siegl, S. Rajaram, M. Serra-Mir, I. Roth, T. Feitas-Simoes, E. Ros, J. Sabaté, 2017. Favourable nutrient intake and displacement with long-term walnut supplementation among elderly: Results of a randomised trial. Br J Nutr. 118(3):201-209.

Abstract: Older adults tend to require fewer energy content and higher levels of nutrients to promote and maintain optimal health. Regrettably, dietary variety and quality are known to decline with advancing age. We conducted a 2-year prospective, randomised, dietary intervention trial where we asked free-living elderly subjects (63–79 years) on self-selected habitual diets to incorporate walnuts daily into their diet (15 % energy). We then compared their nutrient intake with that of a similar group of concurrent participants on self-selected habitual diets but abstaining from walnut consumption (control). No recipes or advice on use of nuts were provided. Dietary intake was assessed by multiple unannounced 24-h telephone dietary recalls. On average, walnut supplement consumption was 43 g/d or 1171·5 kJ (281 kcal). The mean daily energy intake was 954 kJ (228 kcal) higher in the walnut group than in the control group (P<0·001). Compared with control, participants in the walnut group reported significantly higher intake of total protein, vegetable protein, total PUFA and n-3 and n-6 PUFA; and significantly lower intake of total carbohydrate, animal protein, SFA, and Na. An estimated 19 % of total energy and 25 % of total fat from other food sources was displaced. Displacement of MUFA and total PUFA was 21 and 16 %, respectively. Thus adding a daily supplement of walnuts to an ad libitum diet of older adults can induce favourable modifications to the nutrient profile in a way that addresses declining nutrient intake associated with aging.

A walnut-enriched diet reduces lipids in healthy Caucasian subjects, independent of recommended macronutrient replacement and time point of consumption: a prospective, randomized, controlled trial.

Bamberger, C., A. Rossmeier, K. Lechner, L. Wu, E. Waldmann, R.G. Stark, J. Altenhofer, K. Henze, K.G. Parhofer, 2017. A walnut-enriched diet reduces lipids in healthy Caucasian subjects, independent of recommended macronutrient replacement and time point of consumption: a prospective, randomized, controlled trial. Nutrients. Oct 6;9(10). pii: E1097. doi: 10.3390/nu9101097.

Studies indicate a positive association between walnut intake and improvements in plasma lipids. We evaluated the effect of an isocaloric replacement of macronutrients with walnuts and the time point of consumption on plasma lipids. We included 194 healthy subjects (134 females, age 63 ± 7 years, BMI 25.1 ± 4.0 kg/m²) in a randomized, controlled, prospective, cross-over study. Following a nut-free run-in period, subjects were randomized to two diet phases (8 weeks each). Ninety-six subjects first followed a walnut-enriched diet (43 g walnuts/day) and then switched to a nut-free diet. Ninety-eight subjects followed the diets in reverse order. Subjects were also randomized to either reduce carbohydrates (n = 62), fat (n = 65), or both (n = 67) during the walnut diet, and instructed to consume walnuts either as a meal or as a snack. The walnut diet resulted in a significant reduction in fasting cholesterol (walnut vs control: -8.5 ± 37.2 vs. -1.1 ± 35.4 mg/dL; p = 0.002), non-HDL cholesterol (-10.3 ± 35.5 vs. -1.4 ± 33.1 mg/dL; p ≤ 0.001), LDL-cholesterol (-7.4 ± 32.4 vs. -1.7 ± 29.7 mg/dL; p = 0.029), triglycerides (-5.0 ± 47.5 vs. 3.7 ± 48.5 mg/dL; p = 0.015) and apoB (-6.7 ± 22.4 vs. -0.5 ± 37.7; p ≤ 0.001), while HDL-cholesterol and lipoprotein (a) did not change significantly. Neither macronutrient replacement nor time point of consumption significantly affected the effect of walnuts on lipids. Thus, 43 g walnuts/d improved the lipid profile independent of the recommended macronutrient replacement and the time point of consumption.

Prebiotic nut compounds and human microbiota.

Lamuel-Raventos, R.M., M.-P. St. Onge, 2017. Prebiotic nut compounds and human microbiota. Critical Reviews in Food Science and Nutrition. 57(14): 3154–3163.

Nut consumption is clearly related to human health outcomes. Its beneficial effects have been mainly attributed to nut fatty acid profiles and content of vegetable protein, fiber, vitamins, minerals, phytosterols and phenolics. However, in this review we focus on the prebiotics properties in humans of the nonbioaccessible material of nuts (polymerized polyphenols and polysaccharides), which provides substrates for the human gut microbiota and on the formation of new bioactive metabolites and the absorption of that may partly explain the health benefits of nut consumption.

Intermuscular adipose tissue and thigh muscle area dynamics during an 18-month randomized weight loss trial.

Yaskolka, M.A., I. Shelef, D. Schwarzfuchs, Y. Gepner, L. Tene, H. Zelicha, G. Tsaban, A. Bilitzky, O. Komy, N. Cohen, N. Bril, M. Rein, D. Serfaty, S. Kenigsbuch, Y. Chassidim, L. Zeller, U. Ceglarek, M. Stumvoll, M. Blüher, J. Thiery, M.J. Stampfer, A. Rudich, I. Shai, 2016. Intermuscular adipose tissue and thigh muscle area dynamics during an 18-month randomized weight loss trial. J Appl Physiol. 121:518-527.

It remains unclear whether intermuscular adipose tissue (IMAT) has any metabolic influence or whether it is merely a marker of abnormalities, as well as what are the effects of specific lifestyle strategies for weight loss on the dynamics of both IMAT and thigh muscle area (TMA). We followed the trajectory of IMAT and TMA during 18-mo lifestyle intervention among 278 sedentary participants with abdominal obesity, using magnetic resonance imaging. We measured the resting metabolic rate (RMR) by an indirect calorimeter. Among 273 eligible participants (47.8 ± 9.3 yr of age), the mean IMAT was 9.6 ± 4.6 cm(2) Baseline IMAT levels were directly correlated with waist circumference, abdominal subdepots, C-reactive protein, and leptin and inversely correlated with baseline TMA and creatinine (P < 0.05 for all). After 18 mo (86.3% adherence), both IMAT (-1.6%) and TMA (-3.3%) significantly decreased (P < 0.01 vs. baseline). The changes in both IMAT and TMA were similar across the lifestyle intervention groups and directly corresponded with moderate weight loss (P < 0.001). IMAT change did not remain independently associated with decreased abdominal subdepots or improved cardiometabolic parameters after adjustments for age, sex, and 18-mo weight loss. In similar models, 18-mo TMA loss remained associated with decreased RMR, decreased activity, and with increased fasting glucose levels and IMAT (P < 0.05 for all). Unlike other fat depots, IMAT may not represent a unique or specific adipose tissue, instead largely reflecting body weight change per se. Moderate weight loss induced a significant decrease in thigh muscle area, suggesting the importance of resistance training to accompany weight loss programs.

Effects of walnut consumption on mood in young adults-a randomized controlled trial.

Pribis, P., 2016. Effects of walnut consumption on mood in young adults-a randomized controlled trial. Nutrients.  8(11), 668; doi:10.3390/nu8110668.

Abstract: Walnuts contain a number of potentially neuroprotective compounds like vitamin E, folate, melatonin, several antioxidative polyphenols and significant amounts of ω-3 fatty acids. The present study sought to determine the effect of walnuts on mood in healthy volunteers. Sixty-four college students were randomly assigned to two treatment sequences in a crossover fashion: walnut-placebo or placebo-walnut. At baseline mood was assessed using Profiles of Mood States (POMS). Data was collected again after eight weeks of intervention. After six-weeks of washout, the intervention groups followed the diets in reverse order. Data was collected once more at the end of the eight-week intervention period. No significant changes in mood were observed in the analyses with both genders combined and in females. However, we have observed a significant medium effect size improvement in the Total Mood Disturbance score (-27.49%, p = 0.043, Cohen’s d = 0.708) in males. In non-depressed healthy young males, walnuts seem to have the ability to improve mood.

Effects of diet composition on weight loss, metabolic factors and biomarkers in a 1-year weight loss intervention in obese women examined by baseline insulin resistance status.

Rock, C.L., S.W. Flatt, B. Pakiz, E.L.Quintana, D.D. Heath, B.K. Rana, L. Natarajan, 2016. Effects of diet composition on weight loss, metabolic factors and biomarkers in a 1-year weight loss intervention in obese women examined by baseline insulin resistance status. Metabolism. 65(11):1605-1613.

Background: Obesity is a risk factor for postmenopausal breast cancer incidence and pre- and postmenopausal breast cancer mortality, which may be explained by several metabolic and hormonal factors (sex hormones, insulin resistance, and inflammation) that are biologically related. Differential effects of dietary composition on weight loss and these metabolic factors may occur in insulin-sensitive vs. insulin-resistant obese women. Objective. To examine the effect of diet composition on weight loss and metabolic, hormonal and inflammatory factors in overweight/obese women stratified by insulin resistance status in a 1-year weight loss intervention. Methods and Results. Nondiabetic women who were overweight/obese (n = 245) were randomly assigned to a lower fat (20% energy), higher carbohydrate (65% energy) diet; a lower carbohydrate (45% energy), higher fat (35% energy) diet; or a walnut-rich (18% energy), higher fat (35% energy), lower carbohydrate (45% energy) diet. All groups lost weight at follow-up (P < 0.0001), with mean (SEM) percent loss of 9.2 (1.1)% in lower fat, 6.5 (0.9)% in lower carbohydrate, and 8.2 (1.0)% in walnut-rich groups at 12 months. The diet x time x insulin resistance status interaction was not statistically significant in the model for overall weight loss, although insulin sensitive women at 12 months lost more weight in the lower fat vs. lower carbohydrate group (7.5 kg vs 4.3 kg, P = 0.06), and in the walnut-rich vs. lower carbohydrate group (8.1 kg vs 4.3 kg, P = 0.04). Sex hormone binding globulin increased within each group except in the lower carbohydrate group at 12 months (P < 0.01). C-reactive protein and interleukin-6 decreased at follow-up in all groups (P < 0.01). Conclusions. Findings provide some support for differential effects of diet composition on weight loss depending on insulin resistance status. Prescribing walnuts is associated with weight loss comparable to a standard lower fat diet in a behavioral weight loss intervention. Weight loss itself may be the most critical factor for reducing the chronic inflammation associated with increased breast cancer risk and progression.

 

Inclusion of walnut in the diets of adults at risk for type 2 diabetes and their dietary pattern changes: a randomized, controlled, cross-over trial.

Njike VY, Yarandi N, Petraro P, Ayettey RG, Treu JA, Katz DL, 2016. Inclusion of walnut in the diets of adults at risk for type 2 diabetes and their dietary pattern changes: a randomized, controlled, cross-over trial. BMJ Open Diabetes Res Care. 4(1):e000293.

Abstract: Background: In our recently published study, including walnuts in the diets of adults with prediabetes led to overall improvement in diet quality. This report adds to those study findings by examining the food groups displaced during walnut inclusion in the diets of those adults with prediabetes. Methods: Randomized, controlled, modified Latin square parallel design with 2 treatment arms. The 112 participants (31 men, 81 women) were randomly assigned to a diet with or without dietary counseling to regulate calorie intake in a 1:1 ratio. Within each treatment arm, participants were further randomized to 1 of 2 sequence permutations to receive a walnut included diet with 56 g (366 kcal) of walnuts per day and a walnut-excluded diet. Participants in the calorie regulated arm received advice from a dietitian to preserve an isocaloric condition while including walnuts. We analyzed the 12 components of the 2010 Healthy Eating Index to examine dietary pattern changes of study participants. Results: Seafood and plant protein foods intake significantly increased with walnut inclusion, compared with their exclusion (2.14±2.06 vs −0.49±2.33; p=0.003). The ingestion of healthful fatty acids also significantly increased with walnut inclusion, compared with their exclusion (1.43±4.53 vs −1.76±4.80; p=0.02). Dairy ingestion increased with walnut inclusion in the calorie-regulated phase, compared with walnut inclusion without calorie regulation (1.06±4.42 vs −2.15±3.64; p=0.02). Conclusions: Our data suggest that walnut inclusion in the diets of adults at risk for diabetes led to an increase in intake of other healthful foods.

Effects of walnut consumption on colon carcinogenesis and microbial community structure.

Nakanishi, M., Y. Chen, V. Qendro, S. Miyamoto, E. Weinstock, G.M. Weinstock, D.W. Rosenberg, 2016. Effects of walnut consumption on colon carcinogenesis and microbial community structure.Cancer Prev Res. 9(8):692-703.

Walnuts are comprised of a complex array of biologically active constituents with individual cancer-protective properties. Here, we assessed the potential benefit of whole walnut consumption in a mouse tumor bioassay using azoxymethane (AOM). In study 1, a modest reduction (1.3-fold) in tumor numbers was observed in mice fed a standard diet (AIN-76A) containing 9.4% walnuts (15% of total fat). In Study 2, the effects of walnut supplementation were tested in the Total Western Diet (TWD). There was a significant reduction (2.3-fold; p<0.02) in tumor numbers in male mice fed TWD containing 7% walnuts (10.5% of total fat). Higher concentrations of walnuts lacked inhibitory effects, particularly in female mice, indicating there may be optimal levels of dietary walnut intake for cancer prevention. Since components of the Mediterranean diet have been shown to affect the gut microbiome, the effects of walnuts were therefore tested in fecal samples using 16S rRNA gene sequencing. Carcinogen treatment reduced the diversity and richness of the gut microbiome, especially in male mice, which exhibited lower variability and greater sensitivity to environmental changes. Analysis of individual operational taxonomic units (OTUs) identified specific groups of bacteria associated with carcinogen exposure, walnut consumption and/or both variables. Correlation analysis also identified specific OTU-clades that were strongly associated with the presence and number of tumors. Taken together, our results indicate that walnuts afford partial protection to the colon against a potent carcinogenic insult, and this may be due in part to walnut-induced changes to the gut microbiome.

Consumption of walnuts in combination with other whole foods produces physiologic, metabolic, and gene expression changes in obese C57BL/6J high-fat–fed male mice.

Luo, T., O. Miranda-Garcia, A. Adamson, J. Hamilton-Reeve, D.K. Sullivan, J.M. Kinchen, N.F. Shay, 2016.  Consumption of walnuts in combination with other whole foods produces physiologic, metabolic, and gene expression changes in obese C57BL/6J high-fat–fed male mice. J Nutr. 146(9):1641-50.

Background: Although a reductionist approach has sought to understand the roles of individual nutrients and biochemicals in foods, it has become apparent that there can be differences when studying food components in isolation or within the natural matrix of a whole food. Objective: The objective of this study was to determine the ability of whole-food intake to modulate the development of obesity and other metabolic dysfunction in mice fed a high-fat, Western-style obesogenic diet. To test the hypothesis that an n–3 (ω-3) polyunsaturated fatty acid-rich food could synergize with other, largely polyphenol-rich foods by producing greater reductions in metabolic disease conditions, the intake of English walnuts was evaluated in combination with 9 other whole foods. Methods: Eight-week-old male C57Bl/6J mice were fed low-fat (LF; 10% fat) and high-fat (HF) control diets, along with an HF diet with 8.6% (wt:wt) added walnuts for 9 wk. The HF control diet contained 46% fat with added sucrose (10.9%, wt:wt) and cholesterol (1%, wt:wt); the added sucrose and cholesterol were not present in the LF diet. Other groups were provided the walnut diet with a second whole food—raspberries, apples, cranberries, tart cherries, broccoli sprouts, olive oil, soy protein, or green tea. All of the energy-containing whole foods were added at an energy level equivalent to 1.5 servings/d. Body weights, food intake, and glucose tolerance were determined. Postmortem, serum lipids and inflammatory markers, hepatic fat, gene expression, and the relative concentrations of 594 biochemicals were measured. Results: The addition of walnuts with either raspberries, apples, or green tea reduced glucose area under the curve compared with the HF diet alone (−93%, −64%, and −54%, respectively, P < 0.05). Compared with HF-fed mice, mice fed walnuts with either broccoli sprouts or green tea (−49% and −61%, respectively, P < 0.05) had reduced hepatic fat concentrations. There were differences in global gene expression patterns related to whole-food content, with many examples of differences in LF- and HF-fed mice, HF- and walnut-fed mice, and mice fed walnuts and walnuts plus other foods. The mean ± SEM increase in relative hepatic concentrations of the n–3 fatty acids α-linolenic acid, eicosapentanoic acid, and docosapentanoic acid in all walnut-fed groups was 124% ± 13%, 159% ± 11%, and 114% ± 10%, respectively (P < 0.0001), compared with LF- and HF-fed mice not consuming walnuts. Conclusions: In obese male mice, walnut consumption with a high-fat Western-style diet caused changes in hepatic fat concentrations, gene expression patterns, and fatty acid concentrations. The addition of a second whole food in combination with walnuts produced other changes in metabolite concentrations and gene expression patterns and other physiologic markers. Importantly, these substantial changes occurred in mice fed typical amounts of intake, representing only 1.5 servings each food/d.

Greater adherence to the Alternative Healthy Eating Index is associated with lower incidence of physical function impairment in the Nurses’ Health Study.

Hagan, K.A., S.E. Chiuve, M.J. Stampfer, J.N. Katz, F. Grodstein, 2016. Greater adherence to the Alternative Healthy Eating Index is associated with lower incidence of physical function impairment in the Nurses’ Health Study. J Nutr. 146:1341-7.

Background: Physical function is integral to healthy aging, in particular as a core component of mobility and independent living in older adults, and is a strong predictor of mortality. Limited research has examined the role of diet, which may be an important strategy to prevent or delay a decline in physical function with aging. Objective: We prospectively examined the association between the Alternative Healthy Eating Index-2010 (AHEI-2010), a measure of diet quality, with incident impairment in physical function among 54,762 women from the Nurses’ Health Study. Methods: Physical function was measured by the Medical Outcomes Short Form-36 (SF-36) physical function scale and was administered every 4 y from 1992 to 2008. Cumulative average diet was assessed using food frequency questionnaires, administered approximately every 4 y. We used multivariable Cox proportional hazards models to estimate the HRs of incident impairment of physical function. Results: Participants in higher quintiles of the AHEI-2010, indicating a healthier diet, were less likely to have incident physical impairment than were participants in lower quintiles (P-trend < 0.001). The multivariable-adjusted HR of physical impairment for those in the top compared with those in the bottom quintile of the AHEI-2010 was 0.87 (95% CI: 0.84, 0.90). For individual AHEI-2010 components, higher intake of vegetables (P-trend = 0.003) and fruits (P-trend = 0.02); lower intake of sugar-sweetened beverages (P-trend < 0.001), trans fats (P-trend = 0.03), and sodium (P-trend < 0.001); and moderate alcohol intake (P-trend < 0.001) were each significantly associated with reduced rates of incident physical impairment. Among top contributors to the food components of the AHEI-2010, the strongest relations were found for increased intake of oranges, orange juice, apples and pears, romaine or leaf lettuce, and walnuts. However, associations with each component and with specific foods were generally weaker than the overall score, indicating that overall diet pattern is more important than individual parts. Conclusions: In this large cohort of older women, a healthier diet was associated with a lower risk of developing impairments in physical function.