Eating less meat improves cardiovascular health. This is reflected in different studies on diet, which are often hampered by factors such as genetic differences, education and lifestyle choices. To control for these factors, Stanford Medicine researchers conducted a dietary choice study with 22 pairs of identical twins, since they share a genome, grow in the same homes and have a similar lifestyle. They found that a vegan diet improves cardiovascular health in just eight weeks. The results are published this Thursday in ‘JAMA Network Open’.
“Not only did this study provide an innovative way to claim that a vegan diet is healthier than the conventional omnivorous diet, but the twins were also a great pleasure to work with. “They dressed the same, talked the same, and joked with each other in a way that they can only do if they spent an inordinate amount of time together,” says Dr. Christopher Gardner, a professor of medicine at Stanford.
The trial, conducted from May to July 2022, included 22 pairs of healthy, cardiovascular-free identical twins from the Stanford Twin Registry (a database of identical twins who agreed to participate in research studies) and matched one twin from each pair on a vegan or omnivorous diet.
Both diets were healthy, full of vegetables, legumes, fruits and whole grains and devoid of refined sugars and starches. The vegan diet was exclusively plant-based and did not include meat or animal products such as eggs or milk. The omnivorous diet included chicken, fish, eggs, cheese, dairy and other foods of animal origin.
For the first four weeks, one meal service delivered 21 servings per week: seven breakfasts, lunches and dinners. For the remaining four weeks, the participants cooked their food.
They made a dietician available to the twins to offer suggestions and answer questions about diets throughout the duration of the study. Participants were interviewed about their dietary intake and kept a record of the foods they ate.
Forty-three participants completed the study, which Gardner said demonstrates how feasible it is to learn to prepare a healthy diet in four weeks.
«Our study used a generalizable diet that is accessible to anyone, because 21 of the 22 vegans followed the diet. “This suggests that anyone who chooses a vegan diet can improve their long-term health within two months, with the greatest changes seen in the first month,” says Gardner, a professor at the Stanford Prevention Research Center.
The authors found the greatest improvement during the first four weeks of diet change. Participants on a vegan diet had significantly lower levels of ‘bad’ cholesterol (LDL), insulin and body weight than omnivore participants.
At three points in time (at the beginning of the trial, at four weeks, and at eight weeks), the researchers weighed the participants and drew blood. The average baseline level of ‘bad’ cholesterol for vegans was 110.7 mg/dL and 118.5 mg/dL for omnivorous participants; it fell to 95.5 for vegans and 116.1 for omnivores at the end of the study. The optimal healthy LDL level is less than 100.
The vegan participants also showed a about 20% drop in insulin fasting (a high level is a risk factor for developing diabetes) and also They lost an average of 1.9 kilosfurther than omnivores.
“Based on these results and with longevity in mind, most of us would benefit from adopting a more plant-based diet,” says Gardner.
Vegan participants (and omnivores to some extent) did the three most important things to improve cardiovascular health, according to Gardner: They reduced saturated fat consumption, increased dietary fiber, and lost weight.
Gardner emphasizes that although most people probably won’t go vegan, a nudge in the direction of a plant-based diet could improve health. “A vegan diet may confer additional benefits, such as an increase in intestinal bacteria and reduced telomere loss, which slows the aging of the body,” says Gardner.
“What’s more important than becoming strictly vegan is include more plant-based foods in your diet. Having fun with multicultural vegan foods like Indian masala, Asian stir-fries, and African lentil-based dishes can be a great first step,” advises Gardner, who has been “mostly vegan” for the past 40 years.