Generated Summary
This study, published in *JAMA Internal Medicine*, investigates the relationship between plant and animal fat intake and overall and cardiovascular disease (CVD) mortality. The research utilizes data from a large cohort of 407,531 participants and employs Cox proportional hazards regression models to analyze the association between dietary fat intake and the risk of mortality, including mortality due to heart disease and stroke. The study also used cause-specific hazard models and the Fine-Gray model to ensure robustness. The researchers adjusted for various factors, including age, sex, body mass index, race, smoking status, physical activity, and other dietary factors, to isolate the impact of different fat sources. The study further explored whether the associations differed by high versus low protein intake.
Key Findings & Statistics
- The study found that a higher intake of plant fat was associated with a lower risk of overall mortality. For instance, in Model 2 (Multivariable-adjusted), the hazard ratio (HR) for overall mortality was 0.88 (95% CI: 0.86, 0.90) for those in the highest quintile of plant fat intake compared to the reference group.
- Conversely, higher animal fat intake was associated with a higher risk of overall mortality. In the same model, the HR for overall mortality was 1.03 (95% CI: 1.01, 1.05) for those in the highest quintile of animal fat intake.
- The association between plant fat intake and reduced risk of overall mortality was observed across different models. Specifically, in Model 3 (Model 2 + relevant foods), the HR was 0.95 (95% CI: 0.94, 0.97) for overall mortality.
- Regarding CVD mortality, higher plant fat intake was also associated with a lower risk. In Model 2, the HR was 0.92 (95% CI: 0.90, 0.95).
- The study reported an absolute risk difference (ARD) for overall mortality. Specifically, plant fat intake showed a -2.0 (-2.3, -1.7) % ARD.
- For CVD mortality, higher animal fat intake was associated with an increased risk. In Model 2, the HR was 1.04 (1.01, 1.08).
- In the analysis of heart disease mortality, the HR for animal fat in the highest quintile was 1.03 (1.01, 1.05) in Model 3.
- The analyses showed that replacing 5% energy from total animal fat, red meat fat, dairy fat, or egg fat with total plant fat, fat from grains, or vegetable oils, was associated with a 4% to 24% lower risk of overall mortality and a 5% to 30% lower risk of CVD mortality.
- Subgroup analyses revealed that the inverse association of plant fat intake with overall mortality was stronger among younger participants (HR=0.89, 95% CI: 0.85, 0.93, P for interaction=0.0041), and those who consumed 1-3 alcoholic drinks/day (HR=0.89, 95% CI: 0.84, 0.95, P for interaction<0.0001).
- The positive association of animal fat intake with overall mortality seemed to be greater in men (HR=1.16, 95% CI: 1.12, 1.21), participants 60-65 years of age (HR=1.21, 95% CI: 1.14, 1.28), individuals with a lower BMI (<25 kg/m², HR=1.22, 95% CI: 1.16, 1.29), those consuming 1-3 alcoholic drinks/day (HR=1.16, 95% CI: 1.12, 1.21), and during the first 5 years of follow-up (HR=1.37, 95% CI: 1.22, 1.55) (all P for interaction<0.005, Figure 1a).
Other Important Findings
- The positive association of animal fat intake with CVD mortality was stronger among younger participants (HR=1.27, 95% CI: 1.11, 1.44), and during the 5 to 10 year period of follow-up (HR=1.34, 95% CI: 1.14, 1.59) (both P for interaction<0.0001, Figure 1b).
- The study also examined the effects of excluding the initial 2 and 5 years of follow-up. The associations remained consistent, with only slight changes to the HRs, suggesting that the findings were not overly influenced by reverse causality.
- The research explored the effect of adjusting for protein intake from specific foods on the associations, which did not substantially alter the findings.
Limitations Noted in the Document
- The study acknowledges potential limitations related to the observational nature of the study.
- The reliance on self-reported dietary data may introduce measurement errors.
- While the study adjusted for a wide range of covariates, residual confounding may still exist.
- The study excluded participants with a history of diabetes at baseline to reduce the impact of preexisting diseases, but this may limit the generalizability of the findings.
- The study did not include a summary of the subgroup analyses.
- The study was limited to the population in the study, and the findings may not be generalizable to different populations.
Conclusion
The study concludes that higher plant fat intake is associated with a lower risk of overall and CVD mortality, while higher animal fat intake is associated with an increased risk. These findings are consistent across different models and sensitivity analyses, suggesting the robustness of the associations. The results reinforce the importance of dietary recommendations that promote increased consumption of plant-based fats and reduced intake of animal fats for improving cardiovascular health. For instance, substituting 5% energy from animal fat with plant fat led to significantly reduced mortality risk. The subgroup analyses provided nuanced insights into the variability of these associations across different populations. Overall, the study contributes to the evidence base supporting dietary strategies for reducing cardiovascular risk. The findings emphasize the need for considering the source of dietary fat, with a clear advantage to plant-based sources for improved health outcomes. The study results are relevant for public health and clinical guidelines related to dietary recommendations, highlighting the potential benefits of shifting toward diets with lower animal fat and higher plant fat content to improve CVD outcomes.