A public health priority is to identify strategies to promote healthy aging [
More specifically, observational epidemiologic studies and randomized controlled trials provide evidence supporting the association of regular nut consumption with decreased risk in cardiovascular disease and all-cause [
Thus, we utilized the NHS to examine consumption of nuts at midlife and likelihood of subsequent healthy aging in women; as women live longer than men on average, understanding healthy aging in women is particularly important.
The NHS is a prospective cohort study that began in 1976, when female nurses aged 30 to 55 years from 11 US states completed mailed questionnaires. Follow-up questionnaires every two years update information about health and lifestyle; follow-up remains approximately 90%.
In 1980, participants completed a semiquantitative food frequency questionnaire (FFQ) [
To determine the population for analysis in the present study, we used 1998–2002 as the study baseline, corresponding to the years when detailed data on nut consumption were first available. We focused on this relatively early time period for baseline, since we were concerned that, at older ages, underlying health could influence diet choices and lead to bias in analyses. Moreover, scientifically, many chronic diseases and health conditions take years to develop, and thus, it is biologically likely that risk factors at earlier timepoints are most important to later health. We defined healthy aging from the 2012 follow-up questionnaire, which was the first time we collected information simultaneously on chronic diseases, memory concerns, physical function, and mental health from the full cohort. Among the 55,318 nurses who responded to the questions on healthy aging in 2012, we excluded 13,353 women who had already been diagnosed with one of the 11 major chronic diseases of interest (see list below) at study baseline and 7,479 women who did not provide baseline dietary data in 1998 and 2002, as well as 555 women who were missing adequate data to calculate diet quality (AHEI score). Thus, 33,931 participants were included in analyses.
To assess nut consumption at midlife, we averaged nut intake from the FFQs in 1998 and 2002, when more detailed information on nuts was available; thus, 1998–2002 represented our baseline here. Averaging diet over several timepoints provides a measure of longer-term intake (which is likely most relevant to chronic diseases and conditions) and also reduces variability of the measurement. We separately asked participants how often they had consumed (1) peanuts, (2) walnuts, and (3) other nuts (serving size 28 g (1 oz)) during the preceding year: never or almost never, 1 to 3 times a month, once a week, 2 to 4 times a week, 5 or 6 times a week, once a day, 2 or 3 times a day, 4 to 6 times a day, or more than 6 times a day. Consumption of peanut butter was assessed separately, with the same 9 responses (serving size 15 g (1 tablespoon)). Total nut consumption was the sum of peanuts, walnuts, other nuts, and peanut butter. We also examined total nut consumption excluding peanut butter, since peanut butter can contain added oils, such as hydrogenated fats.
To separate “healthy” from “usual” aging, we considered 4 health domains, all measured in 2012. We considered as “healthy” agers women who survived beyond 65 years of age, with no history of chronic diseases, no reported memory impairment, no physical disabilities, and intact mental health; remaining women who survived but did not achieve good health in one or more domains were “usual” agers [
For the chronic disease domain, we considered history of 11 chronic diseases, reported by women on the biennial questionnaires [
The memory domain was assessed with 7 questions (yes/no) to assess memory concerns [
Impairment of physical function was assessed by the SF-36 [
Mental health was assessed through the Geriatric Depression Scale with 15 items (GDS-15) [
Sociodemographic, lifestyle, and health-related covariates (age, educational level, marital status, multivitamin use, aspirin use, smoking, and energy intake) were obtained from the biennial questionnaires; median income was determined from census tract data. All covariates were ascertained in 1998, except the educational level and marital status, which were only available in 1992 and 1996, respectively. Body mass index (BMI) was calculated as weight in kilograms divided by height in meters squared. Physical activity was assessed every 2–4 years by using validated Nurses’ Health Study Physical Activity Questionnaire [
We assessed nut consumption (1998–2002) when nurses were in their late 50 s and early 60 s. To investigate the relation between nut consumption at midlife and healthy aging, we used age-adjusted and multivariable-adjusted logistic regression models. We categorized participants into 5 groups according to frequency of consumption of (i) total nuts and (ii) total nuts excluding peanut butter: never or <1 per month, 1–<4 per month, 1–<2 per week, 2–<3 per week, and ≥3 per week and into 4 groups according to consumption of walnuts, peanuts, other nuts and peanut butter: never or <1 per month, 1–<4 per month, 1–<2 per week, and ≥2 per week. The first logistic regression model was adjusted for age (years), and a second model for age and sociodemographic, lifestyle, and health-related covariates, including education (registered nurse, bachelor’s degree, master, or doctorate), marital status (widowed, married, and single/separated/divorced), median income from census tract (quintiles), BMI (<22, 22–24.9, 25–29.9, and ≥30), energy intake (quintiles of kcal/day), multivitamin use (yes/no), aspirin use (<1, 1–2, or >2 tablets/week), pack-years of smoking (quintiles), and physical activity (quintiles of MET-h/week). The third model was further adjusted for diet quality (AHEI-2010 score, excluding the component of nuts; quintiles).
We conducted several secondary analyses. In one, we slightly revised the “usual aging” definition to add 1,302 women who died during follow-up (i.e., between baseline and 2012), resulting in a reference group of 29,695 rather than 28,393 women. In addition, we conducted analyses separately examining each healthy aging domain (e.g., any chronic disease versus none) in logistic models. All
Of 33,931 women, 5,538 (16%) were considered “healthy” agers; the remaining 28,393 (84%) were “usual” agers (data not shown in table). There was a mix of factors which led to classification as usual aging; that is, one-third of women with usual aging had one or more chronic diseases, and over half had a limitation in functional domains of aging (memory function, mental health, and physical function).
We compared characteristics of healthy versus usual agers at study baseline (Table
Characteristics at study baselinea of usual agers and healthy agers in the Nurses’ Health Study.
Characteristicsb | Healthy agers ( |
Usual agers ( |
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Mean age, years | 58 (4.9) | 62 (6.5) |
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Educational level (1992), % ( |
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Registered nurse | 59 (3267) | 68 (19307) |
Bachelor’s degree | 25 (1385) | 21 (5963) |
Master or doctorate | 16 (886) | 11 (3123) |
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Marital status (1996), % ( |
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Widowed | 5 (277) | 10 (2839) |
Married | 86 (4763) | 82 (23282) |
Separated/divorced | 9 (498) | 8 (2271) |
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Median neighborhood income, $ | 69,517 (27,170) | 64,929 (24,843) |
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Body mass index, % ( |
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<22 | 26 (1440) | 16 (4543) |
22–24.9 | 35 (1938) | 27 (7666) |
25–29.9 | 31 (1717) | 36 (10221) |
≥30 | 8 (443) | 22 (6246) |
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Mean alternate healthy eating index-2010 score (excluding nuts) | 47 (9) | 45 (9) |
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Mean alcohol intake, g/day | 6 (8) | 5 (9) |
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Multivitamin use, % ( |
61 (3378) | 62 (17604) |
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Aspirin use, tablets per week, % ( |
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<1 | 68 (3766) | 62 (17604) |
1‐2 | 7 (388) | 7 (1988) |
>2 | 25 (1384) | 31 (8802) |
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Pack-years of smoking | 7 (12) | 11 (17) |
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Mean physical activity, metabolic equivalent task-hours/week | 26 (27) | 18 (21) |
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History of high blood pressure, % ( |
21 (1163) | 39 (11073) |
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History of high cholesterol, % ( |
39 (4984) | 56 (15900) |
aStudy baseline is 1998 for this table, unless otherwise noted. Measures in table were calculated among nonmissing values (≤5% of data were missing). bData expressed as mean (SD) or as percent.
When we examined the relation of nut consumption at midlife and subsequent odds of healthy aging (Table
Odds of healthy aging, according to frequency of total consumption of nuts at midlife in the Nurses’ Health Study.
Servings (28 grams for nuts and 15 grams for peanut butter) | ||||||
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<1/month | 1–<4/month | 1–<2/week | 2–<3/week | ≥3/week |
| |
Total nuts | ||||||
Healthy agers ( |
6.6 | 21.6 | 21.6 | 14.8 | 35.3 | |
Age-adjusted OR (95% CIs) of healthy vs usual aging | 1.0 (Ref.) | 1.02 (0.90, 1.17) | 1.02 (0.89, 1.16) | 1.05 (0.91, 1.21) | 1.18 (1.04, 1.34) | <0.0001 |
Multivariable-adjusteda OR (95% CIs) of healthy vs usual aging | 1.0 (Ref.) | 1.07 (0.93, 1.24) | 1.04 (0.90, 1.20) | 1.08 (0.93, 1.25) | 1.14 (1.00, 1.31) | 0.031 |
Multivariable-adjustedb OR (95% CIs) of healthy vs usual aging | 1.0 (Ref.) | 1.06 (0.92, 1.22) | 1.02 (0.88, 1.17) | 1.05 (0.90, 1.22) | 1.10 (0.96, 1.26) | 0.160 |
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Total nuts excluding peanut butter | ||||||
Healthy agers ( |
20.8 | 35.2 | 20.2 | 8.2 | 15.6 | |
Age-adjusted OR (95% CIs) of healthy vs usual aging | 1.0 (Ref.) | 1.12 (1.03, 1.22) | 1.17 (1.07, 1.29) | 1.32 (1.17, 1.49) | 1.46 (1.32, 1.62) | <0.0001 |
Multivariable-adjusteda OR (95% CIs) of healthy vs usual aging | 1.0 (Ref.) | 1.10 (1.01, 1.20) | 1.08 (0.97, 1.19) | 1.14 (1.00, 1.31) | 1.21 (1.09, 1.35) | 0.001 |
Multivariable-adjustedb OR (95% CIs) of healthy vs usual aging | 1.0 (Ref.) | 1.08 (0.99, 1.18) | 1.04 (0.94, 1.15) | 1.09 (0.95, 1.25) | 1.14 (1.02, 1.28) | 0.046 |
aLogistic regression model adjusted for age (years), education in 1992 (registered nurse, bachelor’s degree, and master or doctorate), marital status in 1996 (widowed, married, and single/separated/divorced), census tract median income (quintiles), BMI (kg/m2; <22, 22–24.9, 25–29.9, and ≥30), energy intake (quintiles of kcal/day), multivitamin use (yes/no), aspirin use (<1, 1‐2, or >2 tablets/week), pack-years of smoking (quintiles), physical activity (quintiles of METs-h/week), and physical function impairment in 2000 (yes/no). All covariates were collected in 1998 unless stated otherwise. bLogistic regression model further adjusted for Alternative Healthy Eating Index-2010 score (quintiles), excluding nuts as a component.
We also considered each type of nut (peanuts, peanut butter, walnuts, and other nuts) (Table
Odds of healthy aging, according to frequencies of consumption of specific types of nuts at midlife in the Nurses’ Health Study.
Servings (28 grams for nuts) | |||||
---|---|---|---|---|---|
<1 per month | 1–<4 per month | 1–<2 per week | ≥2 per week |
| |
Peanuts | |||||
Healthy agers ( |
39.2 | 45.6 | 7.4 | 7.9 | |
Age-adjusted OR (95% CIs) of healthy vs usual aging | 1.0 (Ref.) | 1.01 (0.94, 1.07) | 1.05 (0.93, 1.18) | 1.20 (1.06, 1.35) | 0.011 |
Multivariable-adjusteda OR (95% CIs) of healthy vs usual aging | 1.0 (Ref.) | 1.00 (0.93, 1.07) | 0.96 (0.85, 1.10) | 1.08 (0.95, 1.22) | 0.524 |
Multivariable-adjustedb OR (95% CIs) of healthy vs usual aging | 1.0 (Ref.) | 0.99 (0.92, 1.06) | 0.94 (0.83, 1.07) | 1.04 (0.92, 1.19) | 0.960 |
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Peanut butter | |||||
Healthy agers ( |
21.5 | 38.8 | 14.6 | 25.2 | |
Age-adjusted OR (95% CIs) of healthy vs usual aging | 1.0 (Ref.) | 0.95 (0.88, 1.03) | 0.94 (0.85, 1.04) | 0.94 (0.86, 1.03) | 0.220 |
Multivariable-adjusted2 OR (95% CIs) of healthy vs usual aging | 1.0 (Ref.) | 1.00 (0.92, 1.09) | 1.01 (0.90, 1.12) | 1.00 (0.91, 1.10) | 0.946 |
Multivariable-adjusted3 OR (95% CIs) of healthy vs usual aging | 1.0 (Ref.) | 1.00 (0.92, 1.09) | 1.00 (0.90, 1.12) | 0.99 (0.90, 1.09) | 0.839 |
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Walnuts | |||||
Healthy agers ( |
51.8 | 40.1 | 4.6 | 3.5 | |
Age-adjusted OR (95% CIs) of healthy vs usual aging | 1.0 (Ref.) | 1.25 (1.17, 1.33) | 1.49 (1.29, 1.73) | 1.63 (1.38, 1.93) | <0.0001 |
Multivariable-adjusteda OR (95% CIs) of healthy vs usual aging | 1.0 (Ref.) | 1.17 (1.10, 1.26) | 1.25 (1.07, 1.47) | 1.28 (1.07, 1.53) | <0.0001 |
Multivariable-adjustedb OR (95% CIs) of healthy vs usual aging | 1.0 (Ref.) | 1.14 (1.07, 1.22) | 1.19 (1.01, 1.39) | 1.20 (1.00, 1.44) | 0.0001 |
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Other nuts | |||||
Healthy agers ( |
47.0 | 39.1 | 7.3 | 6.6 | |
Age-adjusted OR (95% CIs) of healthy vs usual aging | 1.0 (Ref.) | 1.11 (1.04, 1.19) | 1.37 (1.22, 1.55) | 1.35 (1.19, 1.53) | <0.0001 |
Multivariable-adjusteda OR (95% CIs) of healthy vs usual aging | 1.0 (Ref.) | 1.05 (0.98, 1.13) | 1.19 (1.04, 1.36) | 1.09 (0.95, 1.25) | 0.018 |
Multivariable-adjustedb OR (95% CIs) of healthy vs usual aging | 1.0 (Ref.) | 1.03 (0.96, 1.10) | 1.14 (1.00, 1.30) | 1.03 (0.90, 1.18) | 0.205 |
aLogistic regression model adjusted for age (years), education in 1992 (registered nurse, bachelor’s degree, master, or doctorate), marital status in 1996 (widowed, married, and single/separated/divorced), census tract median income tract (quintiles), BMI (kg/m2; <22, 22–24.9, 25–29.9, and ≥30), energy intake (quintiles), multivitamin use (yes/no), aspirin use (<1, 1–2, or >2 tablets/week), pack-years of smoking (quintiles), physical activity (quintiles of METs-h/week), and physical function impairment in 2000 (yes/no). All covariates were collected in 1998 unless stated otherwise. bLogistic regression model further adjusted for Alternative Healthy Eating Index-2010 score (quintiles) excluding the component of nuts.
In secondary analyses (data not shown in table), on adding women who died during follow-up to the “usual aging” group, the results remained highly similar; for example, for total nut intake, the odds ratio for 3 + servings/week versus <1/month remained 1.10 and the overall
In this large cohort of women, we observed a significant association between consumption of nuts at midlife and healthy aging, broadly defined across four domains—chronic diseases, mental health, and cognitive and physical function. When analyzing several specific types of nuts, walnut consumption appeared to have the strongest relation with healthy aging. Importantly, our findings that nut consumption is associated with broad-based health in aging is particularly relevant to public health and suggests that small dietary changes have potential as simple and relatively inexpensive approaches to promote health and well-being in aging.
Our findings are consistent with scientific literature supporting cardiometabolic benefits of nuts [
Our study has limitations. First, in this observational study, confounding is a limitation; however, we considered a broad array of potential confounding factors, including overall diet quality. In addition, the homogeneity of our population of nurses reduces confounding by many factors (such as health consciousness and healthcare access) and helps to provide strong internal validity. Third, nut intake was self-reported and some measurement errors are inevitable. However, we administered a validated FFQ to assess nut consumption, and averaged consumption over two reports, four years apart, which decreases variability; moreover, it is most likely that this error was random; thus, the error would have led to bias to the null or an underestimate of relations between nuts and healthy aging.
Our study has strengths, including a large sample size, the long duration of follow-up, the high follow-up, and the comprehensive, multidomain evaluation of healthy aging. Importantly, the long follow-up period allowed us to evaluate nut consumption at midlife, a critical period of initiation and development for many aging conditions.
In summary, we found that consumption of nuts at midlife was related to a greater likelihood of overall health and well-being at older ages. The association was particularly robust for walnuts, a source of alpha-linolenic acid and ellagitannins. Since many health conditions of aging develop over decades and, thus, earlier lifestyle factors likely have the most influence on later health, our results support the notion that long-term consumption of nuts, a fairly low-cost dietary intervention, merits further confirmation as a strategy contributing to healthier lifespan.
The Nurses’ Health Study data used to generate the results in this manuscript are available upon request. Procedures to access data are described at
The funding agencies had no input in the study design, data collection, analyses, or writing and submission of the manuscript. Aleix Sala-Vila and Francine Grodstein have received unrestricted research funds through their institutions from the California Walnut Commission, Folsom, U.S. Dr. Grodstein has received an unrestricted research award from Nestle Waters, Inc, Paris, France.
The authors declare that they have no conflicts of interest.
Tania-Marisa Freitas-Simoes and Maude Wagner contributed equally to this work. Francine Grodstein, Tania-Marisa Freitas-Simoes, Maude Wagner, and Cecilia Samieri designed the research. Francine Grodstein conducted research. Tania-Marisa Freitas-Simoes and Maude Wagner analysed the data. Tania-Marisa Freitas-Simoes, Maude Wagner, Cecilia Samieri, Aleix Sala-Vila, and Francine Grodstein wrote the manuscript. All authors had primary responsibility for the final content. All authors read and approved the final manuscript.
The Nurses’ Health Study was supported by the NIH (grant UM1CA186107). An unrestricted research award from the California Walnut Commission, Sacramento, CA, US, was provided to Francine Grodstein. A fellowship award from the Instituto de Salud Carlos III Miguel Servet in Spain (grant CP12/03299) was given to Aleix Sala-Vila.