Aging
Telomeres, thought to only ever shorten, lengthened on plant-based diets
LongerTelomeres lengthened on a plant-based program, though they were thought never to grow back
Plant-based diets slow signs of aging. In one program, telomeres, the caps that protect our chromosomes, actually grew longer[4], and in identical twins, a vegan diet slowed biological aging clocks in just eight weeks[1]. Women who ate the most plant protein were far more likely to age without major disease[3], and older vegans needed fewer prescription drugs[9]. If you want to age well, you would stop eating animals.
What the evidence says
The main points first. Every claim is tied to a source below.
Telomeres, thought to only shorten with age, grew longer on a plant-based program
Telomeres are the caps on the ends of chromosomes, and they were thought to only shorten with age, never grow back[1]. Ornish followed men with low-risk prostate cancer through a plant-based lifestyle program[1]. After three months they had more telomerase, the enzyme that rebuilds telomeres[1][2], and after five years their telomeres were longer, while the comparison group’s had gotten shorter[1]. The sample was small, and the program also included walking and stress management, so diet wasn’t the only change[1].
Read full article →Observational studies also link plant-rich diets with longer telomeres
In a 2024 study, Li and colleagues found that a plant-based diet rich in vegetables, fruit, whole grains, and legumes was linked with longer telomeres, while a diet heavy in junk plant foods was not[1]. In the Nurses’ Health Study, Crous-Bou and colleagues found that among 4,676 women, those who followed a plant-rich Mediterranean diet more closely had longer telomeres[2]. A 2025 review in Nutrients gathered more observational studies like these[3]. The Ornish trial showed telomeres actually getting longer, and these larger studies, though observational, agree with it[1][2].
Read full article →Eight weeks on a vegan diet slowed aging clocks in identical twins
In the Twins Nutrition Study, one twin from each pair ate a vegan diet and the other an omnivore diet for eight weeks[1]. Only the vegan twins showed a drop in epigenetic age acceleration on the GrimAge, PhenoAge, and DunedinPACE clocks, and their scores for inflammation, heart, liver, and metabolism improved too[1]. The trial was short and the group small[1].
Read full article →Healthy plant-based diets were linked with slower epigenetic aging, and junk-food ones weren’t
Kim and colleagues tested four plant-based diet scores against epigenetic aging clocks[1]. The overall, provegetarian, and healthy plant-based scores were linked with slower aging on GrimAge2[1]. An “unhealthy plant” score, which counts fries and soda as plants, was not[1]. The benefit comes from vegetables, beans, and whole grains, and vegan cookies won’t give it to you.
Read full article →Among 48,000 women, more plant protein in midlife was linked with healthier aging
In the Nurses’ Health Study, women who ate the most plant protein in midlife were 46% more likely to reach older age with fewer chronic diseases, better mobility, and less cognitive decline[1]. Getting more protein from meat and dairy was linked with more chronic disease[1].
Read full article →One month of vegan eating changed aging-related marks on DNA
In a one-month vegan trial, DNA methylation patterns changed in ways tied to immune cells, inflammation, and two clocks used to predict health outcomes[1]. One month can’t tell us about a lifetime, but it shows how quickly the body responds[1].
Read full article →Older vegans took 58% fewer prescription drugs
In the Polypharma Study of older adults, a vegan diet was linked with 58% fewer prescription drugs than a non-vegetarian diet, after adjusting for other factors[1]. Needing fewer pills in old age is a rough sign of having fewer diagnosed problems that doctors treat with drugs[1]. It’s a single study[1].
Read full article →Articles
Plant-based eating slows biological aging
Women who ate the most plant protein in midlife were 46% more likely to reach old age in good health. A vegan diet slowed epigenetic aging clocks in identical twins, and on a plant-based program, telomeres, long thought only to shorten, actually grew longer.
Read full article →
Sources
Papers and datasets. Each card keeps its caveats, including small samples and single-animal cases.
[1]BMC Medicine, 2024 · Clinical
Eight weeks of vegan eating slowed epigenetic aging in identical twins
In the Twins Nutrition Study, one twin in each identical pair ate vegan and the other ate an omnivorous diet for eight weeks. Only the vegan twins showed significant drops in epigenetic age acceleration (GrimAge, PhenoAge, and DunedinPACE) and in aging scores for inflammation, heart, liver, and metabolism. The trial was small and short.
[2]PubMed, 2026 · Observational
Higher plant-based diet scores were linked with slower epigenetic aging
Kim and colleagues found that higher scores on the overall, provegetarian, and healthy plant-based diet indexes were linked with slower aging on GrimAge2, an epigenetic clock. The unhealthy plant-based index, which is built on junk food, showed no such link. So diets rich in plants and low in animal products may slow biological aging.
[3]Harvard T.H. Chan / American Journal of Clinical Nutrition, 2024 · Observational
Women who ate the most plant protein were 46% more likely to age healthily
Harvard researchers followed more than 48,000 women in the Nurses’ Health Study from midlife. Those who ate the most plant protein were 46% more likely to age healthily, with fewer chronic diseases, better physical function, and less cognitive decline, while more protein from meat and dairy was linked with more chronic disease.
[4]The Lancet Oncology, 2013 · Small sample
Telomeres grew longer in men on Ornish’s plant-based program
Telomeres were thought only to shorten with age. In Ornish’s study, men with low-risk prostate cancer on a plant-based lifestyle program had more telomerase at three months and longer telomeres at five years, while the control group’s telomeres got shorter. The sample was small, and the program also included walking and stress management.
[5]Clinical Nutrition, 2024 · Observational
Healthy plant-based diets were linked with longer telomeres
In Li’s study, a plant-based diet rich in vegetables, fruit, whole grains, and legumes was linked with longer telomeres. A plant-based diet built on junk food wasn’t.
[6]BMJ, 2014 · Observational
Women who ate a plant-rich Mediterranean diet had longer telomeres
Crous-Bou and colleagues studied 4,676 women in the Nurses’ Health Study and found that those who stuck more closely to a plant-rich Mediterranean diet had longer telomeres.
[7]UC San Diego, 2026 · Clinical
One month on a vegan diet shifted DNA methylation tied to aging and inflammation
UC San Diego reported on a one-month randomized trial in which a vegan diet shifted DNA methylation patterns tied to immune cells and inflammation. Two epigenetic clocks that predict health outcomes suggested biological aging slowed over that month.
[8]Nature Medicine, 2025 · Observational
Plant-rich diets scored best for healthy aging in a Nature Medicine study
A Nature Medicine analysis of long-term diet and healthy aging found that plant-rich eating patterns scored best.
[9]International Journal of Environmental Research and Public Health, 2021 · Observational
Older vegans were prescribed 58% fewer pills
In the Polypharma Study of older adults, a vegan diet was linked with 58% fewer prescription drugs than a non-vegetarian diet after adjustment (IRR 0.42). It’s a single study, but needing fewer pills in later life is a rough sign of aging with fewer diagnosed problems that doctors treat with drugs.