Archive

Research Nut: Walnuts

Associations between nut consumption and health vary between omnivores, vegetarians, and vegans.

Brown, R.C., A.R. Gray, S.L. Tey, A. Chisholm, V. Burley, D.C. Greenwood, J. Cade, 2017. Associations between nut consumption and health vary between omnivores, vegetarians, and vegans. Nutrients. 7, 9, 1219; doi:10.3390/nu9111219.

Regular nut consumption is associated with reduced risk factors for chronic disease; however, most population-based studies lack consideration of effect modification by dietary pattern. The UK Women’s Cohort Study (UKWCS) provides an ideal opportunity to examine relationships between nut consumption and chronic disease risk factors in a large sample with diverse dietary patterns. Nut and nutrient intake from 34,831 women was estimated using a food frequency questionnaire among self-identified omnivores, vegetarians and vegans. In this cross-sectional analysis, higher nut consumption was associated with lower body weight (difference between highest and lowest consumption categories from adjusted model: 6.1kg; 95% CI: 4.7,7.6) body mass index (BMI, 2.4 units difference; 95% CI:1.9,2.9), and waist circumference (2.6cm difference; 95% CI:1.4,3.8) (all ρ for linear trend<0.001). Higher nut consumption was also associated with reduced prevalence of high cholesterol and high blood pressure; having a history of heart attack, diabetes and gallstones; and markers of diet quality (all adjusted ρ for linear trend ≤ 0.011). Higher nut consumption appeared over all to be associated with greater benefits amongst omnivores compared to vegetarians and vegans. Findings support existing literature around beneficial effects of nut consumption and suggest that benefits may be larger among omnivores. Nut promotion strategies may have the highest population impact by specifically targeting this group.

Longitudinal analysis of nut-inclusive diets and body mass index among overweight and obese African American women living in rural Alabama and Mississippi, 2011–2013.

Sterling, S.R., B. Bertrand, S. Judd, T.L. Carson, P. Chandler-Laney, M.L. Baskin, 2017. Longitudinal analysis of nut-inclusive diets and body mass index among overweight and obese African American women living in rural Alabama and Mississippi, 2011–2013. Prev Chronic Dis 2017;14:160595. DOI: https://doi.org/10.5888/pcd14.160595.

Introduction: Nuts, when eaten alongside other nutritionally rich foods, may decrease obesity and related chronic disease risks, which are high among African American women in the rural South. We monitored changes in nut intake, other obesity-related foods (fruits, vegetables, red or processed meats, added sugars), and body mass index (BMI) over a 2-year weight loss intervention among 383 overweight and obese African American women in rural Alabama and Mississippi. Methods: Two dietary recalls were administered at 4 points over 24 months. Mann–Whitney tests compared differences in median food group intake between nut consumers and non-nut consumers, and t tests identified BMI differences between groups. Mixed linear models tested the relationship between nut intake and intake of the select food groups, and between nut intake and BMI over time. Results: Overall nut consumers ate more fruits and vegetables and less red meat than non-nut consumers. Nut consumers had lower BMI values than non-nut consumers. Weight loss by the end of the intervention was significant for nut consumers but not for non-nut consumers, even after accounting for kilocalorie consumption and physical activity engagement. Conclusion: Nut consumption is associated with consumption of other nutritionally rich foods and lower BMI among African American women in rural Alabama and Mississippi. Future interventions should target increasing daily nut intake, decreasing added sugar intake, and identifying strategies to encourage positive dietary changes to continue after an intervention.

Intramyocellular triacylglycerol accumulation across weight loss strategies; Sub-study of the CENTRAL trial.

Gepner, Y., I. Shelef, D. Schwarzfuchs, N. Cohen, N. Bril, M. Rein, G. Tsaban, H. Zelicha, A. Yaskolka Meir, L. Tene, B. Sarusy, P. Rosen, J.R. Hoffman, J.R. Stout, J. Thiery, U. Ceglarek, M. Stumvoll, M. Blüher, M.J. Stampfer, I. Shai, 2017. Intramyocellular triacylglycerol accumulation across weight loss strategies; Sub-study of the CENTRAL trial. PLoS One. 2017 Nov 30;12(11):e0188431. doi: 10.1371/journal.pone.0188431. eCollection 2017.

BACKGROUND: Intramyocellular triacylglycerol (IMTG) is utilized as metabolic fuel during exercise and is linked to insulin resistance, but the long-term effect of weight loss strategies on IMTG among participants with abdominal fat, remain unclear. METHODS: In an 18-month trial, sedentary participants with abdominal fat/dyslipidemia were randomized to either a low-fat (LF) or Mediterranean/low-carbohydrate (MED/LC) diet (including 28g·day-1 of walnuts). After 6-months, the participants were re-randomized to moderate intense physical activity (PA+) or non-physical activity (PA-). Magnetic resonance imaging (MRI) was used to quantify changes of IMTG, abdominal sub-depots, hepatic and intermuscular fats. RESULTS: Across the 277 participants [86% men, age = 48 years, body-mass-index (BMI) = 31kg/m2, visceral fat = 33%] 86% completed the 18-m trial. At baseline, women had higher IMTG than men (3.4% vs. 2.3%, p<0.001) and increased IMTG was associated with aging and higher BMI, visceral and intermuscular fats, HbA1c%, HDL-c and leptin (p<0.05), but not with intra-hepatic fat. After 18 month of intervention and a -3 kg mean weight loss, participants significantly increased IMTG by 25%, with a distinct effect in the MED/LCPA+ group as compared to the other intervention groups (57% vs. 9.5-18.5%, p<0.05). Changes in IMTG were associated with visceral and intermuscular fat, metabolic syndrome, insulin and leptin (p<0.05 for all), however, these associations did not remain after adjustment for visceral fat changes. CONCLUSIONS: Lifestyle strategies differentially affect IMTG accumulation; combination of exercise with decreased carbohydrate/increased unsaturated fat proportion intake greatly increase IMTG. Our findings suggest that increased IMTG during diet-induced moderate weight loss may not be directly related to cardiometabolic risk.

Effectiveness of a walnut-enriched diet on murine sperm: involvement of reduced peroxidative damage.

Coffua, L.S., P.A. Martin-Deleon, 2017. Effectiveness of a walnut-enriched diet on murine sperm: involvement of reduced peroxidative damage. Heliyon. 2017 Feb 20;3(2):e00250. doi: 10.1016/j.heliyon.2017.e00250.

Abstract: A walnut supplement for a Western-style diet in men was shown to improve sperm motility, vitality, and morphology. To gain further insights into factors underlying this improvement, we administered a parallel walnut-enriched diet to mice [including those with a defect in sperm motility due to deletion of Plasma Membrane Ca2+-ATPase 4 (Pmca4−/−)] to determine if there is a similar improvement that is accompanied by reduced sperm membrane peroxidative damage. Although sperm vitality and acrosome reaction rate were unaffected, the diet led to a significant improvement in motility (P < 0.05) and morphology (P < 0.04) in wild-type sperm and in morphology (P < 0.01) in Pmca4−/−, confirming the diet’s efficacy, which appeared to be more modest in mice than in humans. In both strains of mice, the diet resulted in a significant decrease in sperm lipid peroxidation (oxidative stress) levels, but did not rescue the significantly increased apoptotic levels seen in the testis and epididymis of Pmca4 nulls. Our findings support the effectiveness of walnuts on sperm quality, associated with reduced peroxidative damage; and suggest that oxidative stress is involved in the mechanism(s) underlying male reproductive defects in Pmca4−/−.

Changes in the gut microbial communities following addition of walnuts to the diet.

Byerley, L.O., D. Samuelson, E. Blanchard, M. Luo, B.N. Lorenzen, S. Banks, M.A. Ponder, D.A. Welsh, C.M. Taylor, 2017. Changes in the gut microbial communities following addition of walnuts to the diet. J Nutr Biochem. 48:94-102.

Walnuts are rich in omega-3 fatty acids, phytochemicals and antioxidants making them unique compared to other foods. Consuming walnuts has been associated with health benefits including a reduced risk of heart disease and cancer. Dysbiosis of the gut microbiome has been linked to several chronic diseases. One potential mechanism by which walnuts may exert their health benefit is through modifying the gut microbiome. This study identified the changes in the gut microbial communities that occur following the inclusion of walnuts in the diet. Male Fischer 344 rats (n=20) were randomly assigned to one of two diets for as long as 10 weeks: 1) walnut (W), and 2) replacement (R) in which the fat, fiber, and protein in walnuts were matched with corn oil, protein casein, and a cellulose fiber source. Intestinal samples were collected from the descending colon, the DNA isolated, and the V3-V4 hypervariable region of 16S rRNA gene deep sequenced on an Illumina MiSeq for characterization of the gut microbiota. Body weight and food intake did not differ significantly between the two diet groups. The diet groups had distinct microbial communities with animals consuming walnuts displaying significantly greater species diversity. Walnuts increased the abundance of Firmicutes and reduced the abundance of Bacteriodetes. Walnuts enriched the microbiota for probiotic-type bacteria including Lactobacillus, Ruminococcaceae, and Roseburia while significantly reducing Bacteroides and Anaerotruncus. The class Alphaproteobacteria was also reduced. Walnut consumption altered the gut microbial community suggesting a new mechanism by which walnuts may confer their beneficial health effects.

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.