Identical Twins Study Shows Vegan Diets Helping the Heart

A new study of identical twins has provided fresh evidence that a vegan diet can vastly improve a person’s heart health.

Twins assigned a vegan diet for two months had significant improvements in cholesterol, insulin and body weight compared to their siblings, who ate a healthy diet that included animal protein.

“Based on these results and thinking about longevity, most of us would benefit from going to a more plant-based diet,” said researcher Christopher Gardner, a professor of medicine at the Stanford University School of Medicine.

It’s well-known that cutting back on meat consumption improves heart health, but differences between participants in diet studies — things like genetics, upbringing and lifestyle choices — make it hard for researchers to draw definitive conclusions.

Gardner and his colleagues chose to study identical twins because they share the same genetics, grew up in the same household and often have 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,” Gardner noted in a university news release. “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.”

The research team recruited 22 pairs of identical twins to participate in a diet-based clinical trial that ran from May to July 2022. The twins all were listed in the Stanford Twin Registry, a database of fraternal and identical twins who’ve agreed to participate in research studies.

One twin from each pair was assigned a vegan diet, and the other an omnivore diet.

Both diets were healthy, containing lots of vegetables, beans, fruits and whole grains. The diets also limited sugars and refined starches.

But the vegan diet was entirely plant-based, containing neither meat nor animal products like eggs or milk. The omnivore diet included chicken, fish, eggs, cheese, dairy, and other foods from animal sources.

For the first four weeks, a meal service delivered three meals a day. During the remaining four weeks, participants prepared their own meals.

Out of the 44 people in the study, 43 followed it through to completion, Gardner said.

“Our study used a generalizable diet that is accessible to anyone, because 21 out of the 22 vegans followed through with the diet,” said Gardner, who is also a professor in the Stanford Prevention Research Center. “This suggests that anyone who chooses a vegan diet can improve their long-term health in two months, with the most change seen in the first month.”

Average “bad” LDL cholesterol levels dropped steadily for the vegans and stayed about the same for the omnivores.

Vegans also saw a 20% decrease in their fasting insulin levels, and lost an average of 4 more pounds than the omnivores.

The findings were published Nov. 30 in the journal JAMA Network Open.

Gardner acknowledged that most people are unlikely to go vegan, but said even a nudge in the plant-based direction could improve their health.

“What’s more important than going strictly vegan is including more plant-based foods into your diet,” said Gardner, adding he’s been “mostly vegan” for the last 40 years. “Luckily, having fun with vegan multicultural foods like Indian masala, Asian stir-fry and African lentil-based dishes can be a great first step.”

More information

Harvard Medical School has more about vegan diets.

SOURCE: Stanford University, news release, Nov. 28, 2023