Nut consumption and risk of stroke in US male physicians

doi:10.1016/j.clnu.2010.03.005

Clinical Nutrition

Volume 29, Issue 5, October 2010, Pages 605-609

https://doi.org/10.1016/j.clnu.2010.03.005 Get rights and content

Summary

Background & aims

While nut consumption has been shown to lower the risk of hypertension and coronary disease, it is not known whether nut consumption is associated with the risk of stroke. We sought to examine whether nut consumption is associated with total and subtypes of stroke.

Methods

Prospective cohort of 21,078 participants from the Physicians’ Health Study (1982–2008) who were free of stroke at baseline. Nut consumption was assessed using a simple 19-item food questionnaire and stroke cases were confirmed after reviewing medical records. We used Cox’s proportional hazards regression to estimate relative risks of total, ischemic, and hemorrhagic stroke according to consumption of any nuts.

Results

During a mean follow up of 21.1 years, 1424 incident cases of stroke occurred (219 hemorrhagic, 1189 ischemic, and 16 of undetermined cause). There was no statistically significant association between nut consumption and total or ischemic stroke. In contrast, there was a suggestive non-linear relation between nut intake and hemorrhagic stroke: compared to subjects who did not consume nuts, multivariable-adjusted hazard ratios (95% CI) for hemorrhagic stroke for subjects consuming nuts <1, 1, 2–4, 5–6, and ≥7 times/week were 1.13 (0.78–1.62), 1.05 (0.70–1.58), 0.49 (0.27–0.89), 1.50 (0.79–2.84), and 1.84 (0.95–3.57), respectively (p for quadratic trend 0.12).

Conclusions

Our data showed no association between nuts and ischemic stroke and suggested a J-shaped relation between nut consumption and hemorrhagic stroke. Replication of our findings in the general population is warranted.

Introduction

Despite a decline in the rate of stroke in the US,1, 2 it remains a major public health issue and is associated with disability, mortality, and major direct and indirect costs.3, 4 This underscores the importance of prevention strategies aiming at reducing the incidence of stroke given the limited acute treatment options. Hypertension is a major risk factor for stroke⁵ and can be influenced by modifiable lifestyle factors including diet. Among dietary factors, nuts are important source of macro- and micronutrients with health benefits⁶ as they are low in sodium and also contain a variety of nutrients including unsaturated fatty acids, and minerals such as magnesium and potassium. Previous studies have suggested that nuts may have beneficial effects on blood pressure,7, 8, 9 lipids,10, 11 and insulin sensitivity.¹² In a feeding trial, a Mediterranean diet enriched with 30 g/d of nuts (walnuts – 15 g/d, hazelnuts – 7.5 g/d, and almonds – 7.5 g/d) was associated with reduced blood pressure compared to low-fat diet.¹³ We have previously reported an inverse relation between nut intake and hypertension in male physicians.¹⁴ It is thus possible that these physiologic effects of nuts may confer a lower risk of stroke among people who consume them on a regular basis. However, there is a lack of data on the relation between nut consumption and the risk of total stroke or stroke subtypes. Since omega-3 fatty acids contained in nuts have been shown to inhibit platelet aggregation,15, 16 it is possible that nut consumption may prevent or attenuate the progression of thrombo-embolic events. The current study sought to prospectively examine whether nut consumption is associated with the risk of total stroke and stroke subtypes.

Section snippets

Study population

Participants in this project were drawn from the Physicians’ Health Study (PHS), which is a completed randomized, double-blind, placebo-controlled trial designed to study low-dose aspirin and beta-carotene for the primary prevention of cardiovascular disease and cancer. A detailed description of the PHS has been published previously.¹⁷ Each participant gave written informed consent and the Institutional Review Board at Brigham and Women’s Hospital approved the study protocol. Of the total

Results

Table 1 presents the crude baseline characteristics of 21,078 study participants according to categories of nut consumption. The mean age was 54.6 ± 9.5 years (range 40.7–86.7). Higher consumption of nuts was associated with a lower prevalence of hypertension and smoking, and a higher proportion of fruit and vegetable, dairy, and breakfast cereal consumption. During the follow up, 1424 new cases of stroke occurred (1189 ischemic, 219 hemorrhagic, and 16 of undetermined cause). Table 2 provides

Discussion

In this large prospective cohort of apparently healthy men at baseline, we found no evidence for an association between nut consumption and the risk of total or ischemic stroke after an average follow up of 21.1 years. For hemorrhagic stroke, we observed suggestive evidence for a J-shaped relation with nut consumption. Despite advances in medical and surgical treatment, stroke is still associated with major disability and is the 3rd leading cause of death. This underscores the importance of

Conflict of interest

None to disclose.

Acknowledgements

We are indebted to the participants in the PHS for their outstanding commitment and cooperation and to the entire PHS staff for their expert and unfailing assistance.

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To assess the association of nuts with mortality and cardiovascular disease (CVD).
The Prospective Urban Rural Epidemiology study is a large multinational prospective cohort study of adults aged 35–70 y from 16 low-, middle-, and high-income countries on 5 continents. Nut intake (tree nuts and ground nuts) was measured at the baseline visit, using country-specific validated FFQs. The primary outcome was a composite of mortality or major cardiovascular event [nonfatal myocardial infarction (MI), stroke, or heart failure].
We followed 124,329 participants (age = 50.7 y, SD = 10.2; 41.5% male) for a median of 9.5 y. We recorded 10,928 composite events [deaths (n = 8,662) or major cardiovascular events (n = 5,979)]. Higher nut intake (>120 g per wk compared with <30 g per mo) was associated with a lower risk of the primary composite outcome of mortality or major cardiovascular event [multivariate HR (mvHR): 0.88; 95% CI: 0.80, 0.96; P-trend = 0.0048]. Significant reductions in total (mvHR: 0.77; 95% CI: 0.69, 0.87; P-trend <0.0001), cardiovascular (mvHR: 0.72; 95% CI: 0.56, 0.92; P-trend = 0.048), and noncardiovascular mortality (mvHR: 0.82; 95% CI: 0.70, 0.96; P-trend = 0.0046) with a trend to reduced cancer mortality (mvHR: 0.81; 95% CI: 0.65, 1.00; P-trend = 0.081) were observed. No significant associations of nuts were seen with major CVD (mvHR: 0.91; 95% CI: 0.81, 1.02; P-trend = 0.14), stroke (mvHR: 0.98; 95% CI: 0.84, 1.14; P-trend = 0.76), or MI (mvHR: 0.86; 95% CI: 0.72, 1.04; P-trend = 0.29).
Higher nut intake was associated with lower mortality risk from both cardiovascular and noncardiovascular causes in low-, middle-, and high-income countries.
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Consumption of approximately 30 g of nuts per day has been associated with various health benefits, including reduced risk of cardiovascular disease, some cancers and type 2 diabetes, improved blood pressure and weight maintenance (Aune et al., 2016; Crews and Vattem, 2015; De Souza et al., 2017; Flores-Mateo et al., 2013; Gopinath et al., 2015; Luo et al., 2014; Mohammadifard et al., 2015; Sabate, 2003; Sabate et al., 2010; Yong et al., 2017). However, much of this evidence is obtained from food frequency questionnaires obtained from population studies focusing on consumption whole nuts, with limited exploration of nut intake from multi-ingredient foods (Bao et al., 2013; Djousse et al., 2010; Guasch-Ferre et al., 2013). Including nut intake from multi-ingredient foods (as well as from whole nuts) would thus produce a more accurate estimation of the dose of nuts associated with favourable health outcomes.
Databases specifying the amount of core foods present in multi-ingredient foods are required to accurately explore the effect of food consumption on health outcomes. Habitual consumption of nuts, a core food, has been associated with reduced risk of cardiovascular disease. However, in Australia, a lack of information on the amount of nuts in different foods including multi-ingredient foods means that estimations of population nut intake may be misrepresented. The aim of this study was to develop a database for the estimation of nut content in Australian single-ingredient and multi-ingredient foods. A nut-specific database based on AUSNUT 2011-13 was developed via a systematic approach, which defined nut content and type for Australian foods and beverages. The nut database identified 236 nuts and nut-containing foods and beverages. Foods were identified in 14 of the 24 major AUSNUT 2011-13 food groups, including ‘Cereal based products and dishes’ and ‘Confectionery and cereal/nut/fruit/seed bars’. Nuts were found in a wide range of foods, highlighting the importance of developing specific databases to facilitate estimation of core food intake. This database can be used to estimate nut intake in the Australian population and explore associations between nut intake and health outcomes.
Dietary Protein and the Risk of Stroke
2015, Foods and Dietary Supplements in the Prevention and Treatment of Disease in Older Adults
Stroke is the fourth leading cause of death in the United States, and one of the leading causes of serious long-term disability. The type of protein one consumes is a modifiable behavior that can have a significant impact on one’s risk of stroke. This chapter reviews dietary protein sources, daily protein requirements, and the relation between major sources of protein in relation to stroke. These sources include those from animal and vegetable sources combined, as well as those, separately, from red and processed meat, poultry, fish, dairy, eggs, nuts, legumes, and grains. A critical review of the literature, including meta-analyses, prospective cohort studies, and clinical trials, is provided to allow for an understanding of current knowledge and to identify gaps in knowledge. The chapter concludes with recommendations for the prevention of stroke through modification of dietary protein intake.
Contribution of Nuts to the Mediterranean Diet
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Like all tree nuts, Mediterranean nuts (almonds, hazelnuts, pine nuts, pistachios, and walnuts) are nutrient-dense foods rich in unsaturated fatty acids, protein, fiber, healthy minerals, tocopherols, phytosterols, and polyphenols. By virtue of their unique composition, nuts beneficially affect health outcomes. Epidemiologic studies have associated nut consumption with a reduced incidence of coronary heart disease (in both sexes) and diabetes (only in women). Randomized clinical trials demonstrate that nut intake has a cholesterol-lowering effect regardless of the background diet, and there is emerging evidence of beneficial effects on insulin sensitivity, oxidative stress, inflammation, and vascular reactivity. The large 5-year PREDIMED trial tested a nut-enriched Mediterranean diet against a control diet for cardiovascular health outcomes in older participants at high risk. Results to date have shown protection from cardiovascular diseases, particularly stroke, diabetes, and the metabolic syndrome. A beneficial effect on intermediate markers such as blood pressure, lipids, insulin resistance, oxidation, and inflammation also has been uncovered in the PREDIMED study. Also, chronic nut intake does not promote weight gain. In conclusion, the evidence is convincing that nuts, an integral component of the Mediterranean diet, are nutrient-rich foods with wide-ranging cardiometabolic benefits.
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Dietary changes are an integral component of LSM aimed at prevention of CVD. Reduction in the consumption of fats and refined carbohydrates along with increased consumption of fiber, nuts, fruits, and vegetables are associated with improvements in glycemic indices; lipid parameters; weight reduction; reduced risk for diabetes and hypertension; and a lower CV mortality [2,4–11]. Of all these different food components, nuts, particularly pistachios, almonds, and walnuts, are known to have numerous health benefits [12–14].
Previous studies have demonstrated beneficial effects of regular consumption of pistachio nuts on glycemic, lipid, and oxidative stress parameters. The aim of this study was to determine its effect on vascular health, which has not been adequately studied so far.
In this open label, randomized parallel-group study, 60 adults with mild dyslipidemia were randomized to lifestyle modification (LSM) alone or LSM with consumption of 80 g (in-shell) pistachios (equivalent to 40 g or 1.5 oz shelled pistachios) daily for 3 mo. Biochemical parameters, brachial artery flow-mediated vasodilation (BAFMD), and carotid-femoral and brachial-ankle pulse wave velocity (cfPWV and baPWV, respectively) were measured before and after the intervention.
At 3 mo, there was no change in any of the clinical or biochemical parameters in the LSM group. However, the patients in the pistachio group had a significant increase in high-density lipoprotein cholesterol (HDL-C; 35.7 ± 8.8 mg/dL versus 37.8 ± 10.1 mg/dL; P = 0.04) and a reduction in low-density lipoprotein cholesterol (137.2 ± 32.6 mg/dL versus 127.6 ± 34.0 mg/dL; P = 0.02), total cholesterol (TC)-to-HDL-C ratio (5.8 ± 1.3 mg/dL versus 5.3 ± 1.1 mg/dL; P = 0.001), and fasting blood sugar (88.8 ± 7.1 mg/dL versus 86.6 ± 6.3 mg/dL; P = 0.05). Additionally, whereas LSM alone was associated with no improvement in BAFMD or PWV, individuals in the pistachio group had significant reduction in left baPWV (1261.7 ± 187.5 cm/sec versus 1192.4 ± 152.5 cm/sec; P = 0.02) and statistically nonsignificant improvement in most other parameters, including BAFMD. As a result, at 3 mo the patients in the pistachio group had lower cfPWV (770.9 ± 96.5 cm/sec versus 846.4 ± 162.0 cm/sec; P = 0.08), lower left baPWV (1192.4 ± 152.5 cm/sec versus 1326.3 ± 253.7 cm/sec; P = 0.05), and lower average baPWV (1208.2 ± 118.4 cm/sec versus 1295.8 ± 194.1 cm/sec; P = 0.08) compared with the LSM group. Two-way analysis of variance revealed significant treatment effect of pistachio consumption on cfPWV, left baPWV, average baPWV, and BAFMD (P = 0.037, 0.01, 0.07, and 0.046, respectively).
The present study demonstrates that regular consumption of pistachio nuts not only improves glycemic and lipid parameters, but also results in improvements in vascular stiffness and endothelial function. Importantly, these improvements were seen in apparently healthy individuals and with a diet (including pistachios) and exercise regimen that every adult individual is expected to follow.
Consumption of nuts and legumes and risk of stroke: A meta-analysis of prospective cohort studies
2014, Nutrition, Metabolism and Cardiovascular Diseases
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Meta-regression analysis showed no variables were significant factors for the association between dietary nut intake and stroke risk. Three studies provided results for stroke types [17,18], and one for total fetal stroke [19]. The SRR for the highest versus lowest level of dietary nut intake was 0.97 (95% CI: 0.84–1.10; Pheterogeneity = 0.838, I2 = 0) for IS and 1.17 (95% CI: 0.54–2.54; Pheterogeneity = 0.036, I2 = 77.3%) for ICH.
The relationships between dietary nuts and legume intake and risk of stroke are inconsistent. We summarized the evidence by a meta-analysis of prospective cohort studies.
We systematically searched the MEDLINE and EMBASE databases up to 31 January 2014. Random-effects models were used to calculate summary relative risks (SRRs) and 95% confidence intervals (CIs). Between-study heterogeneity was assessed using the Cochran's Q and I² statistics.
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The current meta-analysis provides some evidences for the hypothesis that high intake of dietary nut was inversely associated with stroke risk, whereas dietary legumes intake was not associated with stroke risk.

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^☆: Funding: The Physicians’ Health Study is supported by grants CA-34944, CA-40360, CA-097193, HL-26490 and HL-34595 from the National Institute of Health, Bethesda, MD.

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Published by Elsevier Ltd.

Original ArticleNut consumption and risk of stroke in US male physicians☆

Summary

Background & aims

Methods

Results

Conclusions

Introduction

Section snippets

Study population

Results

Discussion

Conflict of interest

Acknowledgements

J Nutr

Clin Nutr

Am J Clin Nutr

Am J Clin Nutr

Am J Clin Nutr

Am J Clin Nutr

Lancet

Am J Clin Nutr

J Clin Epidemiol

Heart disease and stroke statistics–2008 update: a report from the American heart association statistics committee and stroke statistics subcommittee

Circulation

Trends in incidence, lifetime risk, severity, and 30-day mortality of stroke over the past 50 years

JAMA

Lifetime cost of stroke in the United States

Stroke

Predictors of acute hospital costs for treatment of ischemic stroke in an academic center

Stroke

Meta-analysis of hypertension as a risk factor of cerebrovascular disorders in Koreans

J Korean Med Sci

Olive oil and reduced need for antihypertensive medications

Arch Intern Med

Effect of potassium supplementation on blood pressure in African Americans on a low-potassium diet. A randomized, double-blind, placebo-controlled trial

Arch Intern Med

Nutritional effects on blood pressure

Curr Opin Lipidol

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

Diabetes Care

Original Article
Nut consumption and risk of stroke in US male physicians☆