Abstract
Dietary recommendations regarding protein intake have been focused on the amount of protein. However, such recommendations without considering specific protein sources may be simplistic and insufficient. METHODS AND RESULTS: We included 102 521 postmenopausal women enrolled in the Women’s Health Initiative between 1993 and 1998, and followed them through February 2017. During 1 876 205 person-years of follow-up, 25 976 deaths occurred. Comparing the highest with the lowest quintile, plant protein intake was inversely associated with all-cause mortality (hazard ratio [HR], 0.91 [0.86, 0.96]), cardiovascular disease mortality (HR, 0.88 [0.79, 0.97]), and dementia mortality (HR, 0.79 [0.67, 0.94]). Among major protein sources, comparing the highest with the lowest quintile of consumption, processed red meat (HR, 1.06 [1.01, 1.10]) or eggs (HR, 1.14 [1.10, 1.19]) was associated with higher risk of all-cause mortality. Unprocessed red meat (HR, 1.12 [1.02, 1.23]), eggs (HR, 1.24 [1.14, 1.34]), or dairy products (HR, 1.11 [1.02, 1.22]) was associated with higher risk of cardiovascular disease mortality. Egg consumption was associated with higher risk of cancer mortality (HR, 1.10 [1.02, 1.19]). Processed red meat consumption was associated with higher risk of dementia mortality (HR, 1.20 [1.05, 1.32]), while consumption of poultry (HR, 0.85 [0.75, 0.97]) or eggs (HR, 0.86 [0.75, 0.98]) was associated with lower risk of dementia mortality. In substitution analysis, substituting of animal protein with plant protein was associated with a lower risk of all-cause mortality, cardiovascular disease mortality, and dementia mortality, and substitution of total red meat, eggs, or dairy products with nuts was associated with a lower risk of all-cause mortality. CONCLUSIONS: Different dietary protein sources have varying associations with all-cause mortality, cardiovascular disease mortality, and dementia mortality. Our findings support the need for consideration of protein sources in future dietary guidelines.
Generated Summary
This study investigates the association between major dietary protein sources and all-cause and cause-specific mortality in postmenopausal women. It utilized data from the Women’s Health Initiative (WHI), a large prospective cohort study, and examined the relationship between the intake of animal and plant protein, as well as specific protein sources (such as red meat, poultry, eggs, and dairy products), and mortality outcomes. The study included over 100,000 women and followed them for an average of 18 years, allowing for the examination of long-term health impacts. The methodology involved assessing dietary intake through a self-administered food frequency questionnaire and utilizing Cox proportional hazards models to estimate hazard ratios and 95% confidence intervals for mortality associated with protein intake. The analysis adjusted for various demographic, lifestyle, and health factors. Moreover, they estimated the effect of replacing animal protein with plant protein and other sources to investigate the relationship with mortality risk.
Key Findings & Statistics
- Study Population: The study included 102,521 postmenopausal women enrolled in the Women’s Health Initiative between 1993 and 1998, with follow-up through February 2017. During 1,876,205 person-years of follow-up, 25,976 deaths occurred.
- Protein Intake: The median percent intake of total energy from animal protein was 7.5% in the lowest quintile and 16.0% in the highest, while plant protein intake was 3.5% in the lowest and 6.8% in the highest quintile.
- All-Cause Mortality: Plant protein intake was inversely associated with all-cause mortality (HR, 0.91 [0.86, 0.96]). Substituting 5% energy of animal protein with plant protein was associated with a lower risk of all-cause mortality (HR, 0.86; 95% CI, 0.81–0.91).
- CVD Mortality: Plant protein intake was inversely associated with CVD mortality (HR, 0.88 [0.79, 0.97]). Substituting 5% energy of animal protein with plant protein was associated with a lower risk of CVD mortality (HR, 0.78, 95% CI, 0.70–0.87).
- Dementia Mortality: Plant protein intake was inversely associated with dementia mortality (HR, 0.79 [0.67, 0.94]). Substituting 5% energy of animal protein with plant protein was associated with a lower risk of dementia mortality (HR, 0.81, 95% CI, 0.68–0.97).
- Processed Red Meat: Consumption of processed red meat (HR, 1.06 [1.01, 1.10]) or eggs (HR, 1.14 [1.10, 1.19]) was associated with higher risk of all-cause mortality.
- Eggs: Egg consumption was associated with a higher risk of cancer mortality (HR, 1.10 [1.02, 1.19]). Egg consumption was associated with higher risk of cancer mortality (HR, 1.10 [1.02, 1.19]).
- Unprocessed Red Meat, Eggs, Dairy: Unprocessed red meat (HR, 1.12 [1.02, 1.23]), eggs (HR, 1.24 [1.14, 1.34]), or dairy products (HR, 1.11 [1.02, 1.22]) was associated with higher risk of cardiovascular disease mortality.
- Dementia Mortality: Processed red meat consumption was associated with higher risk of dementia mortality (HR, 1.20 [1.05, 1.32]), while consumption of poultry (HR, 0.85 [0.75, 0.97]) or eggs (HR, 0.86 [0.75, 0.98]) was associated with lower risk of dementia mortality.
- Substitution Analysis: Substituting 2 oz equivalent/d of total red meat with nuts (HR, 0.89; 95% CI, 0.81–0.98), eggs (HR, 0.53; 95% CI, 0.45–0.61), dairy products (HR, 0.88; 95% CI, 0.80–0.97), or legumes (HR, 0.86; 95% CI, 0.74–0.99) with nuts was associated with lower risk of all-cause mortality.
Other Important Findings
- The study found that different dietary protein sources have varying associations with all-cause mortality, cardiovascular disease mortality, and dementia mortality.
- Substituting 2 oz equivalent/d of eggs, dairy products or legumes with nuts was associated with lower risk of all-cause mortality.
- In substitution analysis, substituting of animal protein with plant protein was associated with a lower risk of all-cause mortality, cardiovascular disease mortality, and dementia mortality.
- Replacing 5% of energy from animal protein with plant protein showed benefits.
- Unprocessed red meat and dairy products were associated with higher risk of CVD mortality.
- For cause-specific mortality: substituting 2 oz equivalent/d of eggs (HR, 0.44; 95% CI, 0.33–0.58), dairy products (HR, 0.81; 95% CI, 0.67–0.97), or legumes (HR, 0.70; 95% CI, 0.53–0.92) with nuts was associated with lower risk of CVD mortality.
- Egg consumption was associated with higher risk of cancer mortality (HR, 1.10; 95% CI, 1.02–1.19) comparing the highest with the lowest quintile.
- Processed red meat consumption was associated with higher risk of dementia mortality (HR, 1.20; 95% CI, 1.05–1.36).
Limitations Noted in the Document
- The study acknowledges residual confounding as a limitation, despite adjusting for a wide range of covariates.
- Measurement errors in dietary assessment and covariate data were possible, although these are expected to be non-differential.
- Dietary assessment was only at baseline, and dietary habits may have changed over time.
- Lack of detailed information on specific protein sources (e.g., high-fat vs. low-fat dairy, or raw vs. salted nuts) prevented deeper investigation.
- Findings may not apply to women at a younger age, or premenopausal or perimenopausal women, or men.
- The definition of CVD mortality included deaths from all types of CVD instead of mortality from atherosclerotic CVD only.
- The substitution analysis does not reflect real substitution, but rather a mimic of such replacement.
Conclusion
This prospective cohort study involving over 100,000 postmenopausal women revealed significant associations between dietary protein sources and mortality outcomes. The results emphasize the importance of considering the source of protein in relation to health outcomes, rather than focusing solely on the total amount of protein consumed. The study showed that plant protein intake was associated with a lower risk of all-cause, cardiovascular disease, and dementia mortality, underscoring the potential benefits of incorporating more plant-based protein sources into the diet. Moreover, replacing animal protein with plant protein was associated with a lower risk of all-cause mortality, CVD mortality, and dementia mortality, suggesting that the substitution of animal proteins with plant proteins could offer substantial health benefits. The findings on specific protein sources revealed that processed red meat and eggs consumption were associated with higher mortality risk. Additionally, there were increased risks of cardiovascular disease mortality with unprocessed red meat and dairy products, further highlighting the need to consider the source of dietary protein. Furthermore, the study indicated that substituting certain animal protein sources with nuts may have a protective effect, as it was associated with a lower risk of all-cause mortality. The study’s insights support the need for refined dietary guidelines that consider protein sources and provide recommendations for incorporating plant-based proteins into the diet and limiting the intake of specific animal proteins such as processed red meat. The research supports the idea that dietary guidelines worldwide should distinguish healthier choices for dietary protein from unhealthier choices.
IFFS Team Summary
- 102 521 postmenopausal women from Women’s Health Initiative
- between followed starting between 1993 and 1998, until February 2017
- 1 876 205 person‐years of follow‐up, 25 976 deaths
- between followed starting between 1993 and 1998, until February 2017
- 1 876 205 person‐years of follow‐up, 25 976 deaths
- Comparing highest to lowest quintile of plant protein intake
- All cause mortality HR = 0.91
- Cardiovascular mortality HR = 0.88
- Dementia mortality HR = 0.79
- All cause mortality HR = 0.91
- Cardiovascular mortality HR = 0.88
- Dementia mortality HR = 0.79
- Highest to lowest quintile of animal products for all cause mortality
- Process red meat HR = 1.06
- Eggs HR =1.14
- Process red meat HR = 1.06
- Eggs HR =1.14
- Highest to lowest quintile of animal products for cardiovascular mortality
- Unprocessed red meat HR = 1.12
- Eggs HR = 1.24
- Dairy products HR = 1.11
- Unprocessed red meat HR = 1.12
- Eggs HR = 1.24
- Dairy products HR = 1.11
- Highest to lowest quintile of animal products for cancer mortality
- Eggs HR = 1.10
- Eggs HR = 1.10
- Highest to lowest quintile of animal products for dementia mortality
- Processed red meat HR = 1.20
- Poultry HR = 0.85
- Eggs HR = 0.86
- Processed red meat HR = 1.20
- Poultry HR = 0.85
- Eggs HR = 0.86
- Substitution analysis,
- Substituting of animal protein with plant protein was associated with a lower risk of all‐cause mortality, cardiovascular disease mortality, and dementia mortality
- Substitution of total red meat, eggs, or dairy products with nuts was associated with a lower risk of all‐cause mortality
- Substituting of animal protein with plant protein was associated with a lower risk of all‐cause mortality, cardiovascular disease mortality, and dementia mortality
- Substitution of total red meat, eggs, or dairy products with nuts was associated with a lower risk of all‐cause mortality
- Note for animal protein consumption (median intake within quintile)
- Lowest quintile 7.5% of total energy
- Highest was 16.0% of daily energy
- Lowest quintile 7.5% of total energy
- Highest was 16.0% of daily energy
- Note for plant protein consumption (median intake within quintile)
- Lowest quintile 3.5% of total energy
- Highest was 6.8% of daily energy
- Lowest quintile 3.5% of total energy
- Highest was 6.8% of daily energy
- Limitations of benefits / harms for each food consumed must be interpreted with considerations of how much was consumed
- Relatively small increments of plant protein showed benefit, which is impressive.
- Relatively small increments of plant protein showed benefit, which is impressive.
- The study is does not show us
- Which plant proteins offered the most benefits – some may have stronger benefits than the average, and others lower
- Which plant proteins offered the most benefits – some may have stronger benefits than the average, and others lower