Have a heart! Recent research in 22 pairs of identical twins by Stanford Medicine scientists finds that compared to an omnivore diet, a vegan diet improves cardiovascular health in just eight weeks.

While there’s plenty of research to support reducing meat intake to improve heart health, studies are often limited by genetic variants, environmental differences, and lifestyle choices. However, by evaluating identical twins, the researchers were able to control for genetics and lifestyle factors since they grew up in the same home.

According to Christopher Gardner, PhD, the Rehnborg Farquhar Professor and a professor of medicine, "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. "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 was published in JAMA Network Open. The study was co-first authored by Matthew Landry, PhD, a former Stanford Prevention Research Center postdoctoral scholar, now at the University of California, Irvine, and Catherine Ward, PhD, a post-doctoral scholar at the center.

Twin subjects

Research, which included 22 sets of identical twins, was completed from May to July 2022 with 44 total subjects. Healthy participants without cardiovascular disease were picked from the Stanford Twin Registry -- a database of fraternal and identical twins who have agreed to participate in research studies -- and matched one twin from each pair with either an omnivore or vegan diet.

The omnivore and vegan diets were healthy and included plenty of fruits, vegetables, beans, and whole grains and limited amounts of sugars and refined grains. The vegan diet was completely plant-based and was void of meat, eggs, and dairy products. The omnivore diet included fish, poultry, eggs, dairy products, and animal-based foods.

A meal service delivered 21 meals weekly including seven breakfasts, lunches, and dinners during the initial four weeks. The participants made their own meals for the last four weeks of the study.

According to Gardner, a registered dietitian AKA “diet whisperer” was available to provide suggestions and answer questions about the diets throughout the study. Subjects were surveyed about their dietary intake and kept a food log of what they consumed.

Gardner noted that forty-three percent of subjects finished the study, showing how simple it can be to learn to cook a healthy diet in four weeks. She stated, "Our study used a generalizable diet that is accessible to anyone because 21 out of the 22 vegans followed through with the diet,".

Gardner, who is a professor in the Stanford Prevention Research Center noted, "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."

Better health

The Stanford researchers discovered that the most improvement was observed in the first four weeks of diet changes. The subjects on a vegan diet had significantly lower LDL cholesterol (low-density lipoprotein) levels, insulin, and body weight, which are linked with improved cardiovascular health compared to the omnivore subjects.

Subject were weighed and blood was drawn at three time points, the start of the trial, four weeks in and at eight weeks. The average LDL cholesterol at baseline for the vegan subjects was 110.7 mg/dL and 118.5 mg/dL in the omnivore subjects. This level dropped to 95.5 in the vegan group and 116.1 in the omnivore group by the conclusion of the study. An optimal healthy LDL cholesterol is below 100 mg/dL.

Gardner noted that since the subjects started with healthy LDL cholesterol levels, there was less room for change, suggesting that subjects with higher baseline lipids would demonstrate the greatest change.

Vegan subjects also had nearly a 20% drop in fasting insulin. Elevated insulin levels are a risk factor for the development of diabetes. Compared to the omnivores, the vegan participants lost an average of 4.2 more pounds.

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

According to Gardner, the vegans as well as the omnivores reduced saturated fat, increased fiber, and lost weight- the three most important things to improve heart health.

A global touch

While Gardner recognizes that most people won’t go completely vegan, following a more plant-based diet can still improve health. She notes, "A vegan diet can confer additional benefits such as increased gut bacteria and the reduction of telomere loss, which slows aging in the body,".

Gardner has followed a “mostly vegan” diet for the past 40 years and finds that “Having fun with vegan multicultural foods like Indian masala, Asian stir-fry, and African lentil-based dishes can be a great first step."

She is a member of the Stanford Cardiovascular Institute, the Wu Tsai Human Performance Alliance, the Maternal and Child Health Research Institute, and the Stanford Cancer Institute.

The study received funding from the Vogt Foundation; the Stanford Clinical and Translational Science Award; and the National Heart, Lung, and Blood Institute.

Want tips for following a more plant-based diet? Keep reading!

·         Substitute beans for poultry or meat in chili, soups, or stews.

·         Keep frozen vegetables on hand to add to grains, pasta sauce, soup, and other dishes

·         Choose fresh or dried fruit for dessert over sugary treats.

·         Use hummus as a spread for sandwiches in place of mayonnaise

·         Swap soy milk for cow’s milk

·         Eat nuts instead of processed snack foods

·         Cook with olive or canola oil instead of better or lard

·         Keep a bag of raw spinach leaves in the fridge for quick salads

·         Chop peppers, celery, and carrots ahead of time for fast snacks

·         Use red or brown lentils in spaghetti sauce in place of beef

Lisa Andrews, MEd, RD, LD

Reference:

Matthew J. Landry, Catherine P. Ward, Kristen M. Cunanan, Lindsay R. Durand, Dalia Perelman, Jennifer L. Robinson, Tayler Hennings, Linda Koh, Christopher Dant, Amanda Zeitlin, Emily R. Ebel, Erica D. Sonnenburg, Justin L. Sonnenburg, Christopher D. Gardner. Cardiometabolic Effects of Omnivorous vs Vegan Diets in Identical Twins. JAMA Network Open, 2023; 6 (11): e2344457 DOI: 10.1001/jamanetworkopen.2023.44457