Animal vs Plant Protein and Long-Term Health Outcomes: What Cohort Studies and Trials Show
What cohort studies and randomized trials found for animal versus plant protein and outcomes such as mortality, LDL cholesterol and muscle, and what these studies cannot prove.
Content last updated . This page has not been medically reviewed.
Cohort studies: what they found
| Study | Who and how | What it found |
|---|---|---|
| Song and colleagues, 2016 (US) | 131,342 health care professionals, regularly updated food questionnaires [1] | Animal protein was not associated with all-cause mortality (HR 1.02 per 10 percent of energy) but with higher cardiovascular mortality (HR 1.08). Plant protein was associated with lower all-cause mortality (HR 0.90 per 3 percent of energy). These associations were confined to people with at least one unhealthy lifestyle factor. [1] |
| Budhathoki and colleagues, 2019 (Japan) | 70,696 adults aged 45 to 74, followed to 2016 with 12,381 deaths [2] | Animal protein showed no clear association with mortality. Plant protein was associated with lower total mortality. [2] |
| Naghshi and colleagues, 2020 (BMJ) | Meta-analysis of 32 prospective cohort studies [3] | Plant protein: pooled effect size 0.92 for all-cause mortality (95% CI 0.87 to 0.97). Total and animal protein were not significantly associated with cardiovascular or cancer mortality. An extra 3 percent of energy from plant protein was associated with a 5 percent lower risk of death. [3] |
The Naghshi authors concluded that replacing foods high in animal protein with plant protein sources could be associated with longevity. [3] Song and colleagues found that swapping 3 percent of energy from plant protein for processed red meat protein gave a hazard ratio for all-cause mortality of 0.66, against 0.88 for unprocessed red meat. [1] That shows "animal protein" lumps together very different foods.
Trials: what they found
| Trial review | What was compared | Result |
|---|---|---|
| Guasch-Ferre and colleagues, 2017 | 112 trials of at least 3 weeks, plant protein in substitution for animal protein [4] | LDL cholesterol fell by 0.16 mmol/L (moderate-quality evidence). The authors called for more high-quality trials. [4] |
| Lim and colleagues, 2021 | 16 studies of animal versus plant protein for lean mass and strength [5] | No difference in absolute lean mass or muscle strength, but an advantage for animal protein on percent lean mass. Protein intakes were generally above the RDA at baseline. [5] |
| Yimam and colleagues, 2026 | 18 trials of at least 6 months, mostly soy protein versus animal protein [6] | No differences in body composition, strength, physical performance or cardiometabolic measures, as long as an adequate quantity of protein is consumed. [6] |
The two muscle reviews differ slightly on percent lean mass, which is the kind of disagreement explained in Why Protein and Amino Acid Trials Disagree.
Why cohort findings are not proof
- Protein source goes with the whole diet. Song's team noted that choosing a protein source influences other parts of the diet. [1] A link to plant protein may partly reflect those other foods.
- Measurement and confounding. Memory-based food records leave room for error, and the assumption of no residual confounding cannot be verified. [7] A review of nutritional epidemiology says a well-conducted cohort study can simulate a randomized trial when the key confounders are accounted for. [7]
- Trials have limits too. Randomized nutrition trials can suffer biases after the start. [7]
- Proper evidence not found for randomized trials that tested death or heart attacks by protein source. A Europe PMC title search on 2026-10-23 for animal or plant protein with randomized and mortality or cardiovascular terms returned no results.
What official guidance says
The NHS says a healthy balanced diet can include protein from meat, fish, eggs or non-animal sources such as beans and pulses. [8] It adds that eating too much processed and red meat probably increases bowel cancer risk, and advises people who eat more than 90 g (cooked weight) a day of red or processed meat to cut down to 70 g. [8] That advice concerns red and processed meat, not all animal protein. The US Dietary Guidelines 2025 to 2030, as we read the text, advise a variety of protein foods from animal sources, including eggs, poultry, seafood and red meat, and from plant sources such as beans, lentils, nuts, seeds and soy. [9] Canada's Food Guide pages could not be read, so no statement from them is given. For plant protein foods, see Legumes and Plant Protein Sources.Frequently asked questions
Is plant protein better than animal protein for long life?
Cohort studies link more plant protein to lower mortality, but they show association, not cause. [3][7] No randomized trial of mortality by protein source was found in our search.
Does red meat shorten life?
In one US cohort, replacing processed red meat protein with plant protein was associated with lower all-cause mortality. [1] The NHS says too much processed and red meat probably increases bowel cancer risk. [8]
Do I need animal protein to keep muscle?
A review of 16 studies found no difference in absolute lean mass or strength between animal and plant protein. [5] A longer review found no differences when enough total protein was eaten. [6]
Why do studies disagree about animal protein?
One US cohort linked animal protein to higher cardiovascular mortality, a Japanese cohort found no clear association, and a pooled analysis found no significant link with cardiovascular or cancer mortality. [1][2][3]
Who should be careful changing protein sources?
People with kidney disease should follow their care team's advice on protein amount and type. [10] Others with a medical condition, pregnancy or a very restricted diet should ask a clinician or dietitian first.
More details: evidence, limits and cautions
The details behind this page: cautions, limits of the evidence and where sources disagree. Open any note to read it.
Safety and who should ask a clinician
References
- Song M, Fung TT, Hu FB, et al. Association of animal and plant protein intake with all-cause and cause-specific mortality. JAMA Internal Medicine 2016;176(10):1453-1463 (PubMed abstract). Read 2026-10-23.
- Budhathoki S, et al. Association of animal and plant protein intake with all-cause and cause-specific mortality in a Japanese cohort. JAMA Internal Medicine 2019;179(11):1509-1518 (PubMed abstract). Read 2026-10-23.
- Naghshi S, Sadeghi O, Willett WC, Esmaillzadeh A. Dietary intake of total, animal, and plant proteins and risk of all cause, cardiovascular, and cancer mortality: systematic review and dose-response meta-analysis of prospective cohort studies. BMJ 2020;370:m2412 (PubMed abstract). Read 2026-10-23.
- Guasch-Ferre M, et al. Effect of plant protein on blood lipids: a systematic review and meta-analysis of randomized controlled trials. Journal of the American Heart Association 2017;6(12):e006659. Read 2026-10-23.
- Lim MT, Pan BJ, Toh DWK, Sutanto CN, Kim JE. Animal protein versus plant protein in supporting lean mass and muscle strength: a systematic review and meta-analysis of randomized controlled trials. Nutrients 2021;13(2):661 (PubMed abstract). Read 2026-10-23.
- Yimam M, et al. Long-term effects of plant vs. animal protein supplementation on body composition, muscle strength, physical performance, and cardiometabolic risk factors in adults: a systematic review and meta-analysis of randomized controlled trials. Frontiers in Nutrition 2026;13:1813846 (PubMed abstract). Read 2026-10-23.
- Satija A, Yu E, Willett WC, Hu FB. Understanding nutritional epidemiology and its role in policy. Advances in Nutrition 2015;6(1):5-18. Read 2026-10-23.
- NHS (UK): Meat in your diet, page last reviewed 1 May 2024. Read 2026-10-23.
- U.S. Department of Health and Human Services and U.S. Department of Agriculture: Dietary Guidelines for Americans, 2025-2030 (PDF from realfood.gov; read as extracted text). Read 2026-10-23.
- NIDDK (U.S. National Institutes of Health): Eating and nutrition for chronic kidney disease, last reviewed January 2025. Read 2026-10-23.