Stanford Twin Study: Vegan Twin Has Healthier Heart in Just Eight Weeks

Scientists at Stanford Medicine put identical twins on two different diets and found that the twin who went vegan had a significantly healthier heart in just eight weeks than the sibling who kept eating meat.

The study, published today in JAMA Network Open, recruited 22 pairs of healthy adult identical twins. In each pair, one twin ate a healthy vegan diet and the other a healthy omnivore diet that included meat, eggs and dairy. Because identical twins share the same genes (and usually grew up eating the same food), the researchers could rule out a lot of the factors that muddy normal diet studies.

The trial ran from May to July 2022. For the first four weeks, a meal service delivered 21 meals a week to each participant. For the second four weeks, they cooked for themselves.

The results were clear. The vegan twins' average LDL cholesterol (the "bad" kind that clogs arteries) fell from 110.7 mg/dL to 95.5 mg/dL, while the meat-eating twins barely moved, from 118.5 to 116.1. The vegans also saw about a 20% drop in fasting insulin, and lost an average of 4.2lb more than their siblings.

Senior author Christopher Gardner, Rehnborg Farquhar Professor and professor of medicine at Stanford, said:

Not only did this study provide a groundbreaking way to assert that a vegan diet is healthier than the conventional omnivore diet, but the twins were also a riot to work with.

Based on these results and thinking about longevity, most of us would benefit from going to a more plant-based diet.

Gardner's team noted that the vegans ate fewer calories, which may explain part of the weight loss. But the omnivores here weren't eating junk. Both groups ate a healthy diet, and the vegan one still came out on top. And 21 of the 22 vegan twins stuck to it, HealthDay reports, which shows how doable it is.

Heart disease is the world's biggest killer, and the evidence keeps stacking up. Back in 2017 the Journal of the American College of Cardiology found plant protein is significantly more heart-healthy than animal protein, and the largest study of its kind linked meat to nine major diseases. In 2018 the American Association of Clinical Endocrinologists recommended a plant-based diet.

This year has been a strong one for the science. In July an Oxford study found vegan diets cut climate impact by 75%, and even plant-based Novak Djokovic won his 24th Grand Slam at 36.

Same genes, different plates, healthier hearts.