Mortality

Plant protein is linked with a longer life, and animal protein is not

By WhyStopHarmingAnimals.com

People who get more of their protein from plants die at lower rates than people who get it from animals[1][2][5]. The pattern shows up in pooled data on more than 700,000 people[1], in decades of follow-up on American nurses and health professionals[5], in the NIH-AARP cohort[4] and among Adventists[6]. Plant protein tracks with lower all-cause and cardiovascular mortality[1][2]. Animal protein shows no such protection[1][2], and meat, especially red and processed meat, sits on the side of the ledger that goes the wrong way[4][5].

The largest pooled analyses

The biggest single piece of evidence is a dose-response meta-analysis published in the BMJ in 2020[1]. Naghshi and colleagues pooled data on 715,128 people and found plant protein linked with lower all-cause and cardiovascular mortality[1]. The relationship kept going as intake rose: in the dose-response analysis, more plant protein tracked with fewer deaths[1]. Animal protein did not show that protection[1].

A 2020 analysis in the European Journal of Epidemiology combined the Rotterdam cohort with pooled data from other cohorts and came out the same way[2]. Higher plant protein intake went with lower all-cause and cardiovascular mortality[2], animal protein showed no matching benefit[2], and the authors read the result as support for shifting protein from animals to plants[2].

A 2022 systematic review in Nutrients gathered substitution studies in older adults, the kind that ask what happens when one source of protein replaces another[3]. Swapping animal protein for plant protein tracked with lower cardiovascular mortality and less type 2 diabetes[3].

What happens when you make the swap

Substitution models come closest to the question most people are actually asking. Huang and colleagues used the NIH-AARP cohort, reported in JAMA Internal Medicine in 2020, to estimate the effect of replacing animal protein with plant protein[4]. The replacement was linked with about 10% lower overall mortality, in men and in women[4]. The researchers expressed the swap in steps of 3% of energy, which is a unit of measurement and not a recommended stopping point[4]. The drop was larger when the protein being replaced came from eggs or red meat[4]. Since the benefit comes from the swap itself, nothing in the result argues for stopping at a small slice[4].

Song and colleagues reached the same place from a different direction[5]. Drawing on decades of data from the Nurses’ Health Study and the Health Professionals Follow-up Study, they found higher animal protein intake linked with higher mortality, especially in people who already had a risk factor, and higher plant protein linked with lower mortality[5]. Most of the extra risk from animal protein sat with red meat[5]. Total protein didn’t explain the difference; where the protein came from did.

Vegetarians and vegans

The Adventist Health Study-2 compares diets inside one community[6]. Orlich and colleagues followed 73,308 Adventists and reported in JAMA Internal Medicine in 2013 that all vegetarians combined had 12% lower all-cause mortality than nonvegetarians, a hazard ratio of 0.88[6]. Pesco-vegetarians came in at 0.81[6]. Vegans came in at 0.85, with a confidence interval of 0.73 to 1.01, which just crosses 1.0 and leaves the vegan estimate short of statistical significance on its own[6]. The clearest links were with deaths from cardiovascular, kidney and endocrine disease, and the association was stronger in men[6]. The NIH’s summary of the study described lower death rates from cardiovascular disease, diabetes and kidney disorders among the vegetarians.

Adventists already tend not to smoke[6], which takes out one of the largest confounders in diet research. Even in a group that health-conscious to begin with, leaving meat off the plate still went with fewer deaths[6].

Dinu’s 2017 meta-analysis in Critical Reviews in Food Science and Nutrition found vegetarian diets linked with lower ischemic heart disease and cancer incidence[7]. Its pooled estimate for vegan all-cause mortality was a relative risk of 0.88, but it rested on only two cohorts and had a wide interval, so that specific question is still open[7]. The direction matches AHS-2[7].

Chicken is no way out

People cutting back on red meat often switch to chicken. In a competing-risk analysis published in Nutrients, eating more than 300 g of poultry a week was associated with higher all-cause mortality and higher mortality from gastrointestinal cancer[8]. Like the other studies here it is observational, and it gives no support to the idea that a paler meat is a safe middle ground[8].

How far the evidence goes

Every study above is observational or a pooling of observational studies. People who eat more beans and less meat differ from other people in ways that adjustment for smoking, weight and exercise can only partly capture. The vegan-specific estimates, from AHS-2 and from Dinu, are imprecise and don’t settle the question by themselves[6][7].

What the evidence does have is consistency. Adventists[6], American health professionals[5], NIH-AARP participants[4], the Rotterdam cohort[2] and 715,128 people in pooled data[1] all point the same way: more plant protein goes with fewer deaths[1][2][4][5], and animal protein, especially from red meat, eggs and poultry, buys no extra years[1][2][4][5][8]. The protein we need is available from plants, and so is a longer life[1][2][4][5], without the animals who would otherwise be killed for it.