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Original Investigation
July 13, 2020

Association Between Plant and Animal Protein Intake and Overall and Cause-Specific Mortality

Author Affiliations
  • 1Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Department of Health and Human Services, Bethesda, Maryland
JAMA Intern Med. Published online July 13, 2020. doi:10.1001/jamainternmed.2020.2790
Key Points

Question  Does an association exist between dietary protein choice, particularly from various food sources, and long-term overall mortality or cause-specific mortality in the US population?

Findings  In this cohort of 237 036 men and 179 068 women with 16 years of observation and nearly 78 000 deaths, greater intake of plant protein was significantly associated with lower overall mortality and cardiovascular disease mortality independent of several other risk factors.

Meaning  This study provides evidence for public health recommendations regarding dietary modifications in choice of protein sources that may promote health and longevity.

Abstract

Importance  Although emphasis has recently been placed on the importance of high-protein diets to overall health, a comprehensive analysis of long-term cause-specific mortality in association with the intake of plant protein and animal protein has not been reported.

Objective  To examine the associations between overall mortality and cause-specific mortality and plant protein intake.

Design, Setting, and Participants  This prospective cohort study analyzed data from 416 104 men and women in the US National Institutes of Health–AARP Diet and Health Study from 1995 to 2011. Data were analyzed from October 2018 through April 2020.

Exposures  Validated baseline food frequency questionnaire dietary information, including intake of plant protein and animal protein.

Main Outcomes and Measures  Hazard ratios and 16-year absolute risk differences for overall mortality and cause-specific mortality.

Results  The final analytic cohort included 237 036 men (57%) and 179 068 women. Their overall median (SD) ages were 62.2 (5.4) years for men and 62.0 (5.4) years for women. Based on 6 009 748 person-years of observation, 77 614 deaths (18.7%; 49 297 men and 28 317 women) were analyzed. Adjusting for several important clinical and other risk factors, greater dietary plant protein intake was associated with reduced overall mortality in both sexes (hazard ratio per 1 SD was 0.95 [95% CI, 0.94-0.97] for men and 0.95 [95% CI, 0.93-0.96] for women; adjusted absolute risk difference per 1 SD was −0.36% [95% CI, −0.48% to −0.25%] for men and −0.33% [95% CI, −0.48% to −0.21%] for women; hazard ratio per 10 g/1000 kcal was 0.88 [95% CI, 0.84-0.91] for men and 0.86 [95% CI, 0.82-0.90] for women; adjusted absolute risk difference per 10 g/1000 kcal was −0.95% [95% CI, −1.3% to −0.68%] for men and −0.86% [95% CI, −1.3% to −0.55%] for women; all P < .001). The association between plant protein intake and overall mortality was similar across the subgroups of smoking status, diabetes, fruit consumption, vitamin supplement use, and self-reported health status. Replacement of 3% energy from animal protein with plant protein was inversely associated with overall mortality (risk decreased 10% in both men and women) and cardiovascular disease mortality (11% lower risk in men and 12% lower risk in women). In particular, the lower overall mortality was attributable primarily to substitution of plant protein for egg protein (24% lower risk in men and 21% lower risk in women) and red meat protein (13% lower risk in men and 15% lower risk in women).

Conclusions and Relevance  In this large prospective cohort, higher plant protein intake was associated with small reductions in risk of overall and cardiovascular disease mortality. Our findings provide evidence that dietary modification in choice of protein sources may influence health and longevity.

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    4 Comments for this article
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    Plant protein intake and subsequent mortality: a risk assessment
    Tomoyuki Kawada, MD | Nippon Medical School
    Huang et al. conducted a long-term prospective study to examine the effect of plant protein intake on all-cause and cause-specific mortality (1). Higher plant protein intake was significantly associated with small reductions in the risk of all-cause and cardiovascular disease mortality. Risk reduction of all-cause mortality by the replacement of 3% energy from animal protein with plant protein was 10% in both men and women, and risk reduction of cardiovascular disease mortality by the same amount of replacement were 11% in men and 12% in women. The replacement from specific sources such as egg protein and red meat protein with plant protein contributed to larger reduction in mortality, and the authors recommended dietary modifications for keeping health and longevity. The authors cited the following two prospective studies for specifying the significance of their study, and I want to describe the content of two references precisely to improve the understanding the relationship.

    Song et al. reported that high animal protein intake was positively associated with cardiovascular disease mortality and high plant protein intake was inversely associated with all-cause and cardiovascular disease mortality (2). They also recommended substitution of plant protein for animal protein, especially that from processed red meat, for keeping lower mortality. Budhathoki et al. evaluated the association between animal and plant protein intake and all-cause and cause-specific mortality (3). Higher plant protein intake was inversely associated with all-cause and cardiovascular disease mortality, but animal protein intake was not significantly associated with mortality. They also clarified that hazard ratios (95% confidence intervals) of substituting processed meat protein by plant protein for all-cause and cancer mortalities were 0.54 (0.38-0.75) and 0.50 (0.30-0.85), respectively.

    Although small discrepancies of the results existed in these studies, I think that dietary habits of taking plant protein might be related to other desirable lifestyles for keeping health, which would lead to subsequent longevity.


    References

    1. Huang J, Liao LM, Weinstein SJ, Sinha R, Graubard BI, Albanes D. Association Between Plant and Animal Protein Intake and Overall and Cause-Specific Mortality. JAMA Intern Med. 2020 doi:10.1001/jamainternmed.2020.2790

    2. Song M, Fung TT, Hu FB, et al. Association of Animal and Plant Protein Intake With All-Cause and Cause-Specific Mortality. JAMA Intern Med. 2016;176(10):1453-1463. doi:10.1001/jamainternmed.2016.4182

    3. Budhathoki S, Sawada N, Iwasaki M, et al. Association of Animal and Plant Protein Intake With All-Cause and Cause-Specific Mortality in a Japanese Cohort. JAMA Intern Med. 2019;179(11):1509-1518. doi:10.1001/jamainternmed.2019.2806
    CONFLICT OF INTEREST: None Reported
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    Subgroup analysis-Query
    Suryakanta Acharya, MD Radiation Oncology | Swami Vivekananada Cancer Hospital
    The association between plant protein intake and overall mortality was similar across the subgroups of smoking status, diabetes, fruit consumption, vitamin supplement use, and self-reported health status.

    I have query on this, if I am understanding correctly, a smoker & non-smoker have similar risk of death if both are taking similar plant protein. Kindly correct i am wrong.
    CONFLICT OF INTEREST: None Reported
    Re: Subgroup analysis-Query
    Jiaqi Huang, PhD | Division of Cancer Epidemiology and Genetics, National Cancer Institute
    Thank you for your interest in our paper, Dr. Acharya. To answer your question, it does not mean “a smoker & non-smoker have similar risk of death if both are taking similar plant protein”. With the plant protein association being similar across the smoking subgroups, it means that smoking status did not modify the observed protective association for plant protein intake. That is, both smokers and nonsmokers had similar inverse associations between plant protein intake and risk of mortality, not that higher intake led to similar smoker-nonsmoker death rates (which are well-known to differ substantially).
    CONFLICT OF INTEREST: None Reported
    Why does plant protein prevent accidental death?
    George Henderson | Auckland University of Technology
    The authors of the current analysis of data from the NIH-AARP cohort are to be commended for making the hazard ratios for accidental death available, as did the authors of a similar 2009 NIH-AARP analysis.[1, 2]
    Accidental death (defined as death by accidents, adverse effects, suicide, self-inflicted injury, homicide, and legal intervention) was associated with meat-eating in Sinha et al 2009 (though not directly measured in the paper of Huang et al). There was an increased risk associated with higher consumption of red meat (highest vs lowest quintile) in men HR 1.26 (1.04-1.54) p=0.008, but not in women. This
    HR for accidental death was of a similar size to the HR for CVD mortality and several other common causes of death in Sinha 2009; in the current paper it is greater than most at 0.76 (0.61-0.93) p=0.009.
    Could it be that the consumption of plant protein strongly prevents accidents, perhaps because of an effect on cognitive ability? This latter seems unlikely, given that heme iron had a protective association with Alzheimer's disease mortality, 0.84 (0.72,0.97) p=<0.05, in the 2017 NIH-AARP analysis of Etemadi et al, for which accidental death HRs were not supplied.[3]
    Plant protein intake is associated with a healthy lifestyle, and may signify conscientiousness and an aversion to risk-taking, including potential routes of infection exposure and dangerous or polluted occupations. Residual confounding in this case could therefore lead to an inverse association between plant protein intake and accidental and other causes of death. In contrast, consumption of meat, milk products, and cheese contributes to animal protein intake and is related to an unhealthier lifestyle which may include greater risk-taking behavior; residual confounding in this case could therefore lead to a positive association between animal protein intake and accidental and other causes of death. For this reason, it is important that HRs for mortality from injuries and sudden deaths always be provided in studies analyzing dietary behaviours that may be associated with the longevity-promoting trait of contentiousness.[4]


    [1] Huang J, Liao LM, Weinstein SJ, Sinha R, Graubard BI, Albanes D. Association Between Plant and Animal Protein Intake and Overall and Cause-Specific Mortality. JAMA Intern Med. Published online July 13, 2020. doi:10.1001/jamainternmed.2020.2790

    [2] Sinha R, Cross AJ, Graubard BI, Leitzmann MF, Schatzkin A. Meat intake and mortality: a prospective study of over half a million people. Arch Intern Med. 2009;169(6):562-571. doi:10.1001/archinternmed.2009.6

    [3]E temadi A, Sinha R, Ward MH, et al. Mortality from different causes associated with meat, heme iron, nitrates, and nitrites in the NIH-AARP Diet and Health Study: population based cohort study. BMJ. 2017;357:j1957. Published 2017 May 9. doi:10.1136/bmj.j1957

    [4] Hill PL, Turiano NA, Hurd MD, Mroczek DK, Roberts BW. Conscientiousness and longevity: an examination of possible mediators. Health Psychol. 2011;30(5):536-541. doi:10.1037/a0023859
    CONFLICT OF INTEREST: None Reported
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