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Research Nut: Walnuts

Long-term consumption of nuts (including peanuts, peanut butter, walnuts, and other nuts) in relation to risk of frailty in older women: evidence from a cohort study.

Wang, R., M.T. Hannan, M. Wang, A.W. Schwartz, E. Lopez-Garcia, F. Grodstein, 2023. Long-term consumption of nuts (including peanuts, peanut butter, walnuts, and other nuts) in relation to risk of frailty in older women: evidence from a cohort study. J Nutr. 153(3):820-7. https://doi.org/10.1016/j.tjnut.2023.01.003

Background: Adherence to a healthy diet is inversely associated with frailty. However, the relationship between nuts, a key food group of Mediterranean diet, and frailty is unclear. Objectives: This study aimed to evaluate the association between nut consumption and frailty in an aging female population. Methods: This population-based observational study included nonfrail women (60 y old) in the NHS from 11 states of the United States. Outcome was incident frailty, defined as having 3 of the FRAIL components (fatigue, lower strength, reduced aerobic capacity, multiple chronic conditions, and significant weight loss) and assessed every 4 y from 1992 to 2016. From 1990 to 2014, FFQs were used to assess the intakes of peanuts, peanut butter, walnuts (added in 1998), and other nuts at 4-y intervals. Exposure was total nut consumption, calculated as the sum of intakes of peanuts, peanut butter, walnuts, and other nuts and categorized into <1 serving/mo, 1–3 servings/mo, 1 serving/wk, 2 4 servings/wk, and  5 servings/wk. The relations of intakes of peanuts, peanut butter, and walnuts with frailty were also investigated separately. Cox proportional hazards models were used to assess the associations between nut consumption and frailty after adjusting for age, smoking, BMI, EI, diet quality, and medication use. Results: Among 71,704 participants, 14,195 incident frailty cases occurred over 1,165,290 person-years. The adjusted HR (95% CI) for consuming 5 servings/wk of nuts was 0.80 (0.73, 0.87), as compared with <1 serving/mo. Higher intakes of peanuts and walnuts, but not peanut butter, were also inversely associated with frailty. Conclusions: This large prospective cohort study showed a strong and consistent inverse association between regular nut consumption and incident frailty. This suggests that nut consumption should be further tested as a convenient public health intervention for the preservation of health and well-being in older adults.

Key Area: Body Weight and Composition

Adding walnuts to the usual diet can improve diet quality in the United States: diet modeling study based on NHANES 2015–2018.

Spence, L.A., B. Henschel, R. Li, C.D. Tekwe, K. Thiagarajah, 2023. Adding walnuts to the usual diet can improve diet quality in the United States: diet modeling study based on NHANES 2015–2018. Nutrients. 15(2):258. https://doi.org/10.3390/nu15020258

Background: The under-consumption of calcium, potassium, fiber, and vitamin D is considered a U.S. public health concern. Shifts in eating patterns that increase the consumption of vegetables, fruits, whole grains, nuts/seeds, and dairy products can help achieve the recommended intakes of these nutrients, leading to healthier diets. Objective: We assessed the impact of adding 1 ounce (28.35 g) of walnuts to usual diets on diet quality and nutrients of concern, including magnesium, fiber, and potassium. Methods: We utilized 24 h dietary recalls obtained from the What We Eat in America, National Health and Nutrition Examination Survey (NHANES) and modeled the addition of 1 ounce (28.35 g) of walnuts to the usual diets of no-nut consumers. No-nut consumers aged ≥4 years (n = 7757) from the 2015–2018 NHANES study were included. Population percentages with intakes below the estimated average requirement (EAR) values for calcium, magnesium, folate, and vitamin E and above the adequate intake (AI) values for potassium and fiber were examined. Diet quality was assessed using the Healthy Eating Index-2015 (HEI-2015). The National Cancer Institute method was used to estimate the usual and modeled intakes. Significant differences between usual (current) and modeled intakes were determined using non-overlapping 95% confidence intervals. All analyses included sample weights to account for the NHANES survey design. Results: Adding 1 ounce (28.35 g) of walnuts to the usual diet resulted in significant reductions in the percentages of adults with intakes below the EAR for magnesium and folate (69.6% vs. 52.0%; 49.2% vs. 40.6%, respectively), and increased the percentage of adults above the AI for potassium (22.8% vs. 26.5%). A similar trend was observed among children (4–18 years). HEI scores improved significantly from 49.1 (95% CI: 48.0–50.4) to 58.5 (95% CI: 57.5–59.6) in children and from 52.4 (95% CI: 51.0–53.8) to 59.2 (95% CI: 58.0–60.5) in adults. Conclusions: Adding 1 ounce (28.35 g) of walnuts to the usual diet of no-nut consumers improved the diet quality and adequacy of some under-consumed nutrients.

A dietary model of partial meat replacement with walnuts demonstrates changes in the nutrient profile and quality of the United States Population’s Diet.

Spence, L.A., B. Henschel, R. Li, C.D. Tekwe, K. Thiagarajah, 2023. A dietary model of partial meat replacement with walnuts demonstrates changes in the nutrient profile and quality of the United States population’s diet. Nutrients. 15(21):4518. https://doi.org/10.3390/nu15214518

The purpose of the study is to assess the impact of partial meat replacement with walnuts using a dose–escalation approach on nutrient intake and diet quality in the usual US diet. Food modeling was implemented using the nationally representative 2015–2018 National Health and Examination Survey (NHANES), with a focus on non-nut consumers, which included 2707 children and adolescents and 5190 adults. Walnuts replaced meat in a dose-escalating manner (0.5, 1, 1.5, and 2 oz walnuts per day replaced 1, 2, 3, and 4 oz meat, respectively). Diet quality was estimated using the population ratio method of the 2015 Healthy Eating Index. The usual intake of nutrients was estimated using the National Cancer Institute method. Significant differences were determined using non-overlapping 95% confidence intervals. The partial replacement of meat with walnuts demonstrated significant increases in the mean intake of fiber, magnesium, and omega-3 fatty acids and significant decreases in cholesterol and vitamin B12 in the modeled diets for children, adolescents, and adults. Additionally, the partial replacement of meat with walnuts improved overall diet quality. Walnut consumption at 1–2 oz as a replacement for some meat may improve nutrient intake and diet quality across age groups.

Walnut consumption and gut microbial metabolism: Results of an exploratory analysis from a randomized, crossover, controlled-feeding study.

Petersen, K.S., M. Chandra, J.R. Chen See, J. Leister, F. Jafari, A. Tindall, P.M. Kris-Etherton, R. Lamendella, 2023. Walnut consumption and gut microbial metabolism: Results of an exploratory analysis from a randomized, crossover, controlled-feeding study. Clin Nutr. 42(11):2258-2269. https://doi.org/10.1016/j.clnu.2023.09.023

Background & aims: The effect of walnut-related modulation of gut microbiota composition on microbiota functionality is unknown. The aim was to characterize the effect of a walnut-enriched diet (WD), compared to a fatty acid-matched diet devoid of walnuts (WFMD) and a diet where oleic acid replaces alpha-linolenic acid (ORAD), on bacterial gene expression. Methods: A 3-period, randomized, crossover, controlled-feeding study was conducted. Participants were provided a 2-week run-in standard western diet (SWD; 50% kcal carbohydrate, 16% protein, 34% fat, 12% SFA). Following the SWD in random sequence order, participants were provided the WD, WFMD, and ORAD (48% carbohydrate; 17% protein; fat 35%; 7% SFA). The WD contained 18% of energy from walnuts (57 g/d/2100 kcal). The WFMD and ORAD were devoid of walnuts; liquid non-tropical plant oils were included in these diets. Metatranscriptomic analyses were performed as an exploratory outcome. Results: The analytical sample included 35 participants (40% female) with a mean ± SD age of 43 ± 10 y and BMI of 30.3 ± 4.9 kg/m2. The ⍺-diversity of taxa actively expressing genes, assessed by observed species (p = 0.27) and Pielou’s Evenness (p = 0.09), did not differ among the diets. The ⍺-diversity of actively expressed genes was greater following the WD compared to the WFMD and ORAD as assessed by the observed genes and Pielou’s Evenness metrics (p < 0.05). β-Diversity of the actively expressed genes differed following the WD compared to the WFMD (p = 0.001) and ORAD (p = 0.001); β-diversity did not differ between the WFMD and ORAD. Active composition analyses showed increased Gordonibacter (p < 0.001) activity following the WD vs. the ORAD. Greater expression of many genes was observed following the WD compared to the WFMD and ORAD. Following the WD, greater expression of metabolism-related genes encoding glycine amidinotransferase (GATM; K00613) and arginine deiminase (K01478) was observed compared to the WFMD. Greater expression of glycine amidinotransferase (GATM; K00613) by Gordonibacter was also observed following the WD vs. the WFMD and ORAD. Conclusion: Our results suggest walnut intake may increase endogenous production of homoarginine through gut microbiota-mediated upregulation of GATM, which is a novel mechanism by which walnuts may lower cardiovascular disease risk. However, given the exploratory nature replication is needed.