In a study with 22 pairs of identical twins, Stanford Medicine researchers and their colleagues have found that a vegan diet improves cardiovascular health in as little as eight weeks.

Although it’s well-known that eating less meat improves cardiovascular health, diet studies are often hampered by factors such as genetic differences, upbringing and lifestyle choices. By studying identical twins, however, the researchers were able to control for genetics and limit the other factors, as the twins grew up in the same households and reported similar lifestyles.

“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,” said Christopher Gardner, Ph.D., the Rehnborg Farquhar Professor and a professor of medicine. “They dressed the same, they talked the same and they had a banter between them that you could have only if you spent an inordinate amount of time together.”