Vegan Diet Linked to Better Cardiovascular Health in New Study of Identical Twins

In a new study of 22 pairs of adult identical twins, those who were randomly assigned to a plant-based diet, (ie, vegan diet) showed significant improvements in several cardiovascular measures compared to twins assigned to a healthy omnivorous diet.

Findings published in JAMA Network Open show that after 8 weeks, twins in the vegan diet group experienced significant mean decreases in low-density lipoprotein cholesterol (LDL-C) concentration, fasting insulin levels, and body weight. Investigators reported a significant decrease in LDL-C levels among vegan participants as early as 4 weeks.

“Clinicians may consider recommending plant-based diets to reduce cardiometabolic risk factors, as well as aligning with environmental benefits,” wrote senior author Christopher Gardner, PhD, professor of medicine, Stanford University, Palo Alto, California, and colleagues.

There is “abundant evidence from observational and intervention studies,” according to Gardner and coauthors, demonstrating vegan diets are associated with improved cardiovascular health and a reduced risk of cardiovascular disease (CVD). However, most prior studies have been epidemiologic examinations, which are subject to “bias of self-decided vegans who may differ from non-vegans in factors that may influence diet and health.”

The investigators also pointed out that a vegan diet that is not well formulated can include refined carbohydrates and added sugars as components of low-quality plant foods. “In addition, a poorly formulated vegan diet can include low-quality plant foods, such as refined carbohydrates and added sugars,” stated investigators.

Researchers conducted the current study to compare the cardiometabolic effects of a plant-based diet with an omnivorous diet. Both arms were exposed to vegetables, legumes, fruits, whole grains, nuts, and seeds, according to the research team.

“To control for genetic differences that might alter the cardiometabolic effects of diet, we randomly assigned identical twins to follow the 2 diets for 8 weeks,” said Gardner and colleagues.

Participants were provided their diet-specific meals via a meal delivery service from baseline through week 4, and then they prepared their own diet-appropriate food from weeks 5 to 8.

The primary outcome was the difference in LDL-C concentration from baseline to week 8. Secondary outcome measures were changes in cardiometabolic factors (eg, plasma lipids, glucose, insulin levels), plasma vitamin B₁₂ level, and body weight, according to the study.

In total, 22 pairs of identical twins (mean age, 39.6 years; 77.3% women) were enrolled in the study.

FINDINGS

After 8 weeks, investigators found that participants in the plant-based diet group, compared with those in the omnivorous diet group, experienced significant mean decreases in:

• LDL-C concentration (13.9 mg/dL, 95% CI, −25.3 to −2.4);
• fasting insulin level (2.9 IU/mL, 95% CI −5.3 to −0.4); and
• body weight (1.9 kg, 95% CI −3.3 to −0.6).

Notably, “as early as 4 weeks, we observed a significant decrease in mean LDL-C level among vegans compared with omnivores,” added investigators.

However, while participants in the vegan diet group had a higher intake of vegetables and dietary iron, they also had lower protein intake, dietary satisfaction, and intake of dietary cholesterol.

“Clinicians should allow patients to make informed choices that support them to choose which dietary approach is most suitable for them,” wrote Gardner et al. “At a population level, wider adoption of a culturally appropriate dietary pattern that is higher in plant foods and lower in animal foods can promote health and environmental benefits.”

Source: Landry MJ, Ward CP, Cunanan KM, et al. Cardiometabolic effects of omnivorous vs vegan diets in identical twins: A randomized clinical trial. JAMA Netw Open. 2023;6(11):e2344457.