Nice New Paper From The Nurses’ Health Study 1 And 2 And Health Professionals Follow-up Study (total Of 206404 Participants And 54536 Deaths) Finds Higher Adherence To A Planetary Health Diet Index Is Associated With A 23% Lower Risk Of All-cause Mortality And Lower Risk Of

Generated Summary

This document presents findings from the Nurses’ Health Study 1 and 2, and the Health Professionals Follow-up Study, which included a total of 206,404 participants and 54,536 deaths. The study investigates the association between adherence to a Planetary Health Diet Index (PHDI) and the risk of all-cause mortality and cause-specific mortality. The research utilizes a prospective cohort study design, examining the relationship between dietary patterns and health outcomes over time. The methodology includes assessing dietary intake, calculating PHDI scores, and analyzing hazard ratios to quantify the risk associated with different levels of adherence to the PHDI. The study also considers various covariates such as age, race, smoking status, and other lifestyle factors to adjust for potential confounding variables. The scope of the study covers a broad population and aims to provide insights into the impact of dietary choices on overall health.

Key Findings & Statistics

• The study found that higher adherence to the Planetary Health Diet Index (PHDI) is associated with a 23% lower risk of all-cause mortality.
• The multivariable-adjusted hazard ratio (HR) for the highest quintile (Q5) compared to the lowest (Q1) was 0.77 (0.75, 0.80) indicating a significant reduction in mortality risk.
• When using deciles instead of quintiles, stronger reductions in risk were observed, further emphasizing the impact of dietary adherence.
• In the Nurses’ Health Study 1 and 2 (NHS1 & NHS2), the multivariable-adjusted HR for Q5 vs. Q1 was 0.77 (0.75, 0.80)
• In the Health Professionals Follow-up Study (HPFS), the multivariable-adjusted HR for Q5 vs. Q1 was 0.78 (0.74, 0.81).
• The study observed a 23% lower risk of mortality from all causes.
• Cause-specific mortality reductions included: non-trauma causes (23%), cardiovascular disease (14%), cancer (10%), respiratory disease (47%), neurodegenerative disease (28%), and infectious disease (28%).
• When using only a baseline diet assessment, only a 7% reduction in all-cause mortality was observed (vs. 23% with repeated measures).
• The association between adherence to the Planetary Health Diet and mortality risk was consistent across various subgroups, including age, sex, race, smoking status, and alcohol consumption.
• The hazard ratios (HRs) for total mortality were stratified and adjusted for various factors. The HRs (95% CIs) by quintiles of the PHDI for pooled data: Q1 (HR=1), Q2 (HR=0.86 (0.84, 0.88)), Q3 (HR=0.77 (0.75, 0.79)), Q4 (HR=0.69 (0.67, 0.71)), and Q5 (HR=0.59 (0.58, 0.61)).
• In the NHS1 & NHS2 cohorts: Q1 (HR=1), Q2 (HR=0.86 (0.83, 0.89)), Q3 (HR=0.75 (0.72, 0.78)), Q4 (HR=0.68 (0.66, 0.70)), and Q5 (HR=0.58 (0.56, 0.60)).
• In the HPFS cohort: Q1 (HR=1), Q2 (HR=0.86 (0.82, 0.89)), Q3 (HR=0.79 (0.76, 0.82)), Q4 (HR=0.71 (0.68, 0.74)), and Q5 (HR=0.61 (0.59, 0.62)).
• The study used fixed effects meta-analysis based on the Dersimonian-Laird approach.
• Table 3 shows the hazard ratios (95% CIs) for total mortality according to quintiles of PHDI.
• Model 1 (Cumulative average PHDI) shows the following HRs: All causes: 0.77 (0.75, 0.80), Non-trauma causes: 0.77 (0.74, 0.79), Cardiovascular disease: 0.86 (0.81, 0.91), Cancer: 0.90 (0.85, 0.95), Respiratory disease: 0.53 (0.48, 0.59), Neurodegenerative disease: 0.72 (0.67, 0.78), and Infectious disease: 0.78 (0.63, 0.98).
• When assessing the impacts, Greenhouse gas emissions were 29% lower, fertilizer needs 21% lower, cropland use 51% lower, and irrigation water needs were 13% lower for those that adhered the most to this index.
• Subgroup analysis demonstrated consistent inverse associations between the PHDI and total mortality across various subgroups, including age, sex, race, smoking status, alcohol consumption, and other factors, with p for interaction values generally being non-significant (typically >0.05), suggesting the effects of PHDI were consistent across different groups. For example, for age, <75 years HR 0.82 (0.80,0.85) with p = 0.0001 and >=75 years HR 0.85 (0.83,0.87) with p = 0.0001

Other Important Findings

• The study showed that using deciles (10 groups) instead of quintiles (5 groups) of the PHDI led to even stronger reductions in mortality risk.
• The inverse associations between the Planetary Health Diet and mortality risk were observed across all strata of confounding factors (e.g., smoking, alcohol consumption, physical activity), suggesting confounding by those factors is less likely to explain the findings.
• In the European Prospective Investigation into Cancer and Nutrition (EPIC)-Oxford study, the highest adherence to EAT-Lancet diet was associated with a 9% lower risk of all-cause mortality, 28% lower risk of ischemic heart disease, and 59% risk of diabetes than the lowest adherence.
• In the Malmö Diet and Cancer cohort, the highest adherence to the EAT-Lancet diet was associated with 25% lower risk of all-cause mortality, 24% lower risk of cancer mortality, and 32% lower risk of cardiovascular mortality.

Limitations Noted in the Document

• The study notes that when using only a baseline diet assessment, a smaller reduction in all-cause mortality (7%) was observed compared to studies using repeated measures (23%), indicating that single dietary assessments may underestimate the impact of dietary patterns.
• The study acknowledges that the analysis is based on observational data, which may be subject to unmeasured or residual confounding, although the study adjusted for many potential confounders.
• While the study adjusted for many factors, it is possible that some residual confounding exists.
• The study did not provide a detailed list of the specific foods and quantities that make up the PHDI, so it might be difficult to replicate.

Conclusion

The Nurses’ Health Study 1 and 2 and the Health Professionals Follow-up Study provide compelling evidence supporting the benefits of adhering to a Planetary Health Diet (PHDI). The findings demonstrate a significant reduction in all-cause mortality and various cause-specific mortalities, indicating the potential of this dietary pattern to improve overall health and longevity. The study highlights the importance of sustained dietary adherence, as evidenced by the stronger risk reductions observed with repeated dietary assessments. The consistent inverse associations across various subgroups underscore the robustness of the findings. The study’s comparison with other studies, such as the EPIC-Oxford and Malmö Diet and Cancer cohort, further emphasizes the positive health outcomes associated with plant-based diets. The study’s results support the adoption of more plant-based diets, promoting not only individual health but also environmental sustainability. The strong inverse association between the PHDI and mortality risk supports the broader adoption of sustainable dietary patterns for improved population health and environmental outcomes. The research underscores the potential of dietary interventions in reducing the risk of chronic diseases and promoting a healthier, more sustainable future. Furthermore, the study’s findings have implications for public health recommendations, suggesting that promoting diets rich in plant-based foods can contribute to both individual well-being and global sustainability.