Abstract
IMPORTANCE High intake of nuts has been linked to a reduced risk of mortality. Previous studies, however, were primarily conducted among people of European descent, particularly those of high socioeconomic status. OBJECTIVE To examine the association of nut consumption with total and cause-specific mortality in Americans of African and European descent who were predominantly of low socioeconomic status (SES) and in Chinese individuals in Shanghai, China. DESIGN, SETTING, AND PARTICIPANTS Three large cohorts were evaluated in the study. One included 71 764 US residents of African and European descent, primarily of low SES, who were participants in the Southern Community Cohort Study (SCCS) in the southeastern United States (March 2002 to September 2009), and the other 2 cohorts included 134 265 participants in the Shanghai Women’s Health Study (SWHS) (December 1996 to May 2000) and the Shanghai Men’s Health Study (SMHS) (January 2002 to September 2006) in Shanghai, China. Self-reported nut consumption in the SCCS (approximately 50% were peanuts) and peanut-only consumption in the SMHS/SWHS were assessed using validated food frequency questionnaires. MAIN OUTCOMES AND MEASURES Deaths were ascertained through linkage with the National Death Index and Social Security Administration mortality files in the SCCS and annual linkage with the Shanghai Vital Statistics Registry and by biennial home visits in the SWHS/SMHS. Cox proportional hazards regression models were used to calculate hazard ratios (HRs) and 95% CIs. RESULTS With a median follow-up of 5.4 years in the SCCS, 6.5 years in the SMHS, and 12.2 years in the SWHS, 14 440 deaths were identified. More than half of the women in the SCCS were ever smokers compared with only 2.8% in the SWHS. The ever-smoking rate for men was 77.1% in the SCCS and 69.6% in the SMHS. Nut intake was inversely associated with risk of total mortality in all 3 cohorts (all P < .001 for trend), with adjusted HRs associated with the highest vs lowest quintiles of intake being 0.79 (95% CI, 0.73-0.86) and 0.83 (95% CI, 0.77-0.88), respectively, for the US and Shanghai cohorts. This inverse association was predominantly driven by cardiovascular disease mortality (P < .05 for trend in the US cohort; P < .001 for trend in the Shanghai cohorts). When specific types of cardiovascular disease were examined, a significant inverse association was consistently seen for ischemic heart disease in all ethnic groups (HR, 0.62; 95% CI, 0.45-0.85 in blacks; HR, 0.60; 95% CI, 0.39-0.92 in whites; and HR, 0.70; 95% CI, 0.54-0.89 in Asians for the highest vs lowest quintile of nut intake). The associations for ischemic stroke (HR, 0.77; 95% CI, 0.60-1.00 for the highest vs lowest quintile of nut intake) and hemorrhagic stroke (HR, 0.77; 95% CI, 0.60-0.99 for the highest vs lowest quintile of nut intake) were significant only in Asians. The nut-mortality association was similar for men and women and for blacks, whites, and Asians and was not modified by the presence of metabolic conditions at study enrollment. CONCLUSIONS AND RELEVANCE Nut consumption was associated with decreased overall and cardiovascular disease mortality across different ethnic groups and among individuals from low SES groups. Consumption of nuts, particularly peanuts given their general affordability, may be considered a cost-effective measure to improve cardiovascular health.
Generated Summary
This research article is a prospective cohort study that investigates the association between nut/peanut consumption and mortality rates among diverse populations. The study evaluated three large cohorts: the Southern Community Cohort Study (SCCS) in the southeastern United States, the Shanghai Women’s Health Study (SWHS), and the Shanghai Men’s Health Study (SMHS) in Shanghai, China. The SCCS included predominantly low-income African and European descent residents, while the SWHS and SMHS comprised Chinese individuals. The primary objective was to examine the association of nut consumption with total and cause-specific mortality. The study assessed self-reported nut consumption via validated food frequency questionnaires and tracked mortality through linkages with national and local mortality registries. Hazard ratios (HRs) and 95% confidence intervals (CIs) were calculated using Cox proportional hazards regression models to determine the associations.
Key Findings & Statistics
- Study Population and Follow-up: The study included a total of 71,764 participants in the SCCS, 134,265 participants in the SWHS/SMHS. The median follow-up periods were 5.4 years for SCCS, 12.2 years for SWHS, and 6.5 years for SMHS.
- Total Mortality Association: Nut intake was inversely associated with total mortality in all three cohorts.
- SCCS findings: Adjusted HRs for the highest vs. lowest quintiles of nut intake were 0.79 (95% CI, 0.73-0.86) in the US cohort and 0.83 (95% CI, 0.77-0.88) for the Shanghai cohorts.
- Ischemic Heart Disease: A significant inverse association was consistently observed for ischemic heart disease across all ethnic groups (HR, 0.62; 95% CI, 0.45-0.85 in blacks; HR, 0.60; 95% CI, 0.39-0.92 in whites; and HR, 0.70; 95% CI, 0.54-0.89 in Asians).
- Stroke: Associations were found with ischemic stroke (HR, 0.77; 95% CI, 0.60-1.00) and hemorrhagic stroke (HR, 0.77; 95% CI, 0.60-0.99) but were only significant in Asians.
- Nut/Peanut and Total Mortality (SCCS): Among those who ate nuts and peanut butter in SCCS, there were 1473 deaths in the lowest quintile and 1142 deaths in the highest quintile. The adjusted HR was 0.79 (95% CI, 0.73-0.86). When analyzing nut intake only in SCCS, the adjusted HR was 0.73 (0.67-0.79) for the highest quintile. For peanut butter, the HR was 0.86 (0.79-0.94).
- Nut/Peanut and Total Mortality (SMHS/SWHS): In the combined Shanghai studies, those in the highest quintile of peanut intake had an HR of 0.83 (0.77-0.88).
- CVD Mortality: In all ethnic groups, the inverse association was consistent for ischemic heart disease (HR, 0.62 for blacks, 0.60 for whites, and 0.70 for Asians). The inverse association with CVD was significant in all 3 cohorts.
- Cancer Mortality: The study found no significant association between nut consumption and cancer mortality.
- Diabetes Mortality: The study found no significant association between nut consumption and diabetes mortality.
Other Important Findings
- The inverse association between nut consumption and total mortality was predominantly driven by cardiovascular disease mortality.
- The study found that the nut-mortality association was similar for men and women.
- The inverse association between nut consumption and mortality was not modified by the presence of metabolic conditions at study enrollment.
- Nut consumption was associated with decreased overall and cardiovascular disease mortality across different ethnic groups and among individuals from low SES groups.
Limitations Noted in the Document
- The study’s reliance on self-reported data, particularly through food frequency questionnaires, may have introduced recall bias.
- The follow-up time was relatively short, especially in the SCCS and SMHS cohorts, which could have limited the statistical power for certain analyses.
- The study did not have information on tree nut consumption in the SMHS/SWHS, potentially limiting the generalizability of the findings.
- The study was unable to fully account for all potential confounding variables, such as residual confounding.
Conclusion
The study’s findings suggest that nut/peanut consumption is associated with a decreased risk of total mortality and CVD mortality across various ethnic groups, particularly in low-SES populations. The inverse association with total mortality was consistent across all three cohorts. The study emphasizes the affordability of peanuts, suggesting that increased nut consumption could be a cost-effective measure for improving cardiovascular health. The results support previous research and provide evidence that incorporating nuts into the diet, specifically peanuts, may have significant benefits for public health, particularly for those in low-income communities. Despite the limitations, the study underscores the potential public health benefits of nut/peanut consumption, given their affordability. The findings align with previous studies showing similar patterns and suggest that these benefits are consistent across different populations. The results emphasize the importance of diet in reducing mortality risk and supporting cardiovascular health. The consistency of these results across such diverse groups strengthens the implications of nut/peanut consumption, making it a viable component in public health recommendations. It highlights the need for further research into the specific mechanisms behind these effects and emphasizes the need to improve dietary guidelines.
IFFS Team Summary
- 71000 USA residents with low socioeconomic status, 134000 Chinese Shanghai Health Study, self reported nut intake
- Mixed nut intake, but 50% were peanuts among nut eaters
- follow up 5 years for USA residents (77% were current or ex smokers in this low socio-economic group), 6.5 years Chinese Men, 12 years Chinese women.
- comparisons for highest to lowest quintiles of consumption
- 20% less total mortality in highest nut eating group, 38% less ischemic heart disease, 23% less ischemic stroke
- 23% less hemorrhagic stroke only in Chinese group
- many other studies show benefits of nuts, this is most recent and largest trial
- benefits of Mediterranean diet likely has more to do with nuts and olive oil than fish
- affordability of peanuts makes it an attractive health food