by A new study of 22 pairs of identical twins found that, compared to their meat-eating sibling, individuals who followed a vegan diet improved cholesterol, blood sugar and body weight in just eight weeks.
The results, published on November 30 i JAMA Open Network, suggests that anyone—even people who are already relatively healthy—can adopt a vegan diet to improve their long-term health in just two months, according to the authors.
Investigators specifically sought to recruit “living, breathing, walking” identical twins — not people with predictive heart disease risk factors such as high LDL (bad) cholesterol, being overweight or obese, the senior author says Christopher Gardner, PhD, professor with. medicine at the Stanford Prevention Research Center in California.
“Yes, some of the twins were overweight or had high cholesterol, but not many. They were already trim with normal cholesterol. And yet, the vegan group reduced their LDL cholesterol by more than 10 percent and lost weight. We were surprised that it happened so quickly and in a group that didn’t have high LDL cholesterol to begin with,” says Dr. Gardner.
Just 1 Percent of Americans Report Eating a Vegan Diet
A vegan diet excludes all meat (beef, pork, poultry), seafood, and fish, and animal products (dairy and eggs).
In the United States, 4 percent of people reported being vegetarian, and 1 percent were vegan, according to a Gallup poll published in August 2023. The polling company found that women, people who describe themselves as political liberals, and people who report earnings. less than $40,000, per year that is more likely to eat a vegetarian diet.
Linking Made the Study Unique — and Fun for Researchers
The study included 22 pairs of identical twins for a total of 44 participants. All were healthy and free of heart disease from the Stanford Twin Registry, a database of fraternal and identical twins who agreed to participate in research studies. In each pair, one twin was assigned a vegan diet, while the other followed an omnivore diet (a diet that includes meat, animal products such as eggs and cow’s milk, and vegetables).
Both aspects of the study were very fun for the researchers, says Dr. Gardner. “It was so fun to see them all come together. They had great fun, great stories — and were often dressed alike and had the same hairstyles!”
The inclusion of identical twins is a key feature that made this study unique, he says. Most nutrition studies are observational, in part because it’s hard to get people to change the way they eat and stick with it for weeks or months, Gardner says.
Most nutrition studies are looking at the eating habits of vegans, omnivores, or pescatarians, for example, and then reporting whatever health outcomes the study is trying to isolate, he says. “And the obvious downside is that the vegans were probably different from the omnivores for other reasons as well. Not only do they have behaviors that can influence their risk, but genetic factors are also at play, and that’s true of randomized studies as well.”
By using identical twins, researchers could control for genetics and limit other factors, because twins grow up in the same families and report similar lifestyles.
Both the vegan diet and the superfood were healthy
The vegan diet was completely plant based and did not include meat or animal products. The omnivore diet included chicken, fish, eggs, cheese, dairy, and other foods from animal sources.
Another distinctive feature of the study is that both diets were generally healthy and contained vegetables, beans, fruit and whole grains and no refined sugars or starches.
“I’m against nutrition studies that compare the ‘best diet’ to eating a bad diet. That’s an easy thing to beat. We wanted to compare the benefits of a healthy vegan diet to a healthy omnivore diet because it makes the results even stronger,” he says.
During the first four weeks, meal service delivered 21 meals per week – seven breakfasts, lunch and dinner. For the next four weeks, the participants prepared their own meals.
There were several advantages to using the meal service, says Gardner. For one, researchers could be sure there was no confusion about what could be included in the vegan diet, he says.
“It also gave people in the vegan group an opportunity to understand what could be included. It is much more than ‘rabbit’ food or a salad with lettuce. It could be a tofu stir fry with lots of crunchy veggies, a black bean lentil burger, a Mediterranean salad with lots of beans and nuts – all very filling,” says Gardner.
21 out of 22 vegetarians completed the study – another testament to how universal and accessible the diet is, he says.
Vegans Had Greater Drops in Cholesterol, Fasting Blood Sugar, and Weight
Researchers noted that the greatest improvements in heart health occurred within the first four weeks after the dietary change.
The mean baseline LDL-C level was 110.7 milligrams per deciliter (mg/dL) for the vegans and 118.5 mg/dL for the omnivore participants.
It dropped to 95.5 mg/dL for vegans (about a 13 percent reduction) and 116.1 mg/dL for omnivores at the end of the study. The ideal healthy LDL-C level is less than 100 mg/dL.
The vegan participants also showed about a 20 percent drop in fasting insulin (a higher insulin level is a risk factor for developing diabetes) and lost an average of 4.2 pounds more than the omnivores. At the start of the trial, the participants’ average BMI was 25.9 kg/m2, slightly above the healthy BMI range of 18.5 to 24.9 kg/m2, according to the Centers for Disease Control and Prevention (CDC).
Further analysis of the participants’ biological ages (a measure of how old a person is physically and metabolically) found that at the end of the eight-week study, the twins who ate the vegan diet were “slightly younger” biologically than their universal content. their peers, Gardner said in a video about the study.
“Based on these results and considering longevity, most of us would benefit from a more plant-based diet,” he says.
Why Would A Vegan Diet Improve Heart Health?
The vegan participants did the three most important things to improve cardiovascular health, according to Gardner: They cut back on saturated fats, increased dietary fiber, and lost weight.
Most Americans eat about half the recommended amount of fiber, Gardner says.
RELATED: 11 High Fiber Foods to Add to Your Diet
Dietary fiber intake is recommended at 14 grams per 1,000 calories of food. For example, at a reference level of 2,000 calories (which is suitable for some people but not all) the daily intake of dietary fiber should be 28 grams, according to the US Department of Agriculture (USDA).
These findings support existing evidence that a vegetarian or vegan diet is associated with improvements in cardiovascular and all-cause mortality, according to a review published in February 2023 in the report. International Journal of Environmental and Public Health Research.
Although the exact mechanism behind the benefits is not fully understood, it is suspected that the saturated fats in meat and animal products may cause low-grade systemic inflammation that can contribute to heart disease.
Ready to Try a Protein Flip?
If you’re not ready to fully adopt a vegan diet, you can eat more veggies and plant-based protein and less meat by trying a “protein flip,” says Gardner.
“Most Americans think of chicken, beef, or pork as the center of the plate and then the accompanying side dishes are grains and vegetables. The protein flip is putting plants in the center of the plate – the meat is no longer the centerpiece, but a flavoring or a side dish,” he says.
One way to try this is with a bowl, which is popular in student dining halls or supermarket hot bars. “You can build your own. So it might have meat, but it might have tempeh, or tofu, and grains and veggies with it,” he says. The flip doesn’t completely cut out meat protein, but it can help reduce meat consumption, says Gardner.
