by A new study of 22 pairs of identical twins found that, compared to their carnivorous sibling, individuals who followed a vegan diet improved cholesterol, blood sugar, and body weight in just eight weeks.
The findings, published Nov. 30 in Open JAMA Network, suggest that anyone, even people who are already relatively healthy, can adopt a vegan diet to improve their long-term health within two months, according to the authors.
The researchers specifically set out to recruit “living, breathing, walking” identical twins, not people with pre-existing heart disease risk factors, such as high LDL (bad) cholesterol, overweight or obesity, says senior author Christopher Gardner, PhD, professor. of medicine at the Stanford Prevention Research Center in California.
“Yes, some of the twins were overweight or had high cholesterol, but many were not. They were already fine 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 did not have high LDL cholesterol to begin with,” says Dr. Gardner.
Only 1 percent of Americans report following a vegan diet
A vegan diet excludes all meats (beef, pork, poultry), seafood and fish, as well as animal products (dairy and eggs).
In the United States, 4 percent of people say they are vegetarians and 1 percent are vegan, according to a Gallup poll published in August 2023. The polling company found that women, people who describe themselves as Politically liberal and people who report making less than $40,000 a year are more likely to follow a vegetarian diet.
Twinning made the study unique and fun for the researchers
The study included 22 pairs of identical twins for a total of 44 participants. All were healthy and free of heart disease according to 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 omnivorous diet (a diet that includes meat, animal products such as eggs and cow’s milk, and vegetables).
The twin aspect of the study was a lot of fun for the researchers, says Dr. Gardner. “It was so much fun watching them all get together. “They had great jokes, wonderful stories, and often dressed alike and had the same hairstyles.”
Including identical twins is a key aspect that made this study unique, he says. Most nutrition studies are observational studies, in part because it’s difficult to get people to change the way they eat and stick with it for weeks or months, Gardner says.
Most nutritional studies look at the eating habits of vegans, omnivores or Pescatarians, for example, and then report whatever health outcomes the study is trying to isolate, he says. “And the obvious disadvantage is that vegans were probably different from omnivores for other reasons as well. Not only do they have behaviors that can influence their risk, but there are also genetic factors at play, and that applies to randomized studies as well.”
By using identical twins, researchers could control for genetics and limit other factors, because twins grow up in the same homes and have similar lifestyles.
Both the vegan and omnivorous diets were healthy
The vegan diet was exclusively plant-based and did not include meat or animal products. The omnivorous diet included chicken, fish, eggs, cheese, dairy and other foods of animal origin.
Another unique feature of the study was that both diets were generally healthy, containing vegetables, beans, fruits, and whole grains and containing no refined sugars or starches.
“I oppose dietary studies that compare a ‘favored’ diet with a poor diet. That’s something easy to overcome. “We wanted to compare the benefits of a healthy vegan diet to a healthy omnivorous diet because it makes the findings even more compelling,” she says.
For the first four weeks, one meal service delivered 21 meals per week: seven breakfasts, lunches and dinners. For the remaining four weeks, participants prepared their own meals.
Using catering had some benefits, Gardner says. For one thing, researchers could be sure there was no confusion about what could be included in the vegan diet, she says.
“It also gave people in the vegan group a chance to understand what might 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 vegetables, a lentil and black bean burger, a Mediterranean salad with lots of beans and nuts, all very filling,” says Gardner.
A total of 21 of 22 vegan consumers completed the study, another testament to how generalizable and accessible the diet is, he says.
Vegans had greater drops in cholesterol, fasting blood sugar and weight
The researchers noted that the greatest improvements in heart health occurred within the first four weeks after the diet change.
The average baseline LDL-C level was 110.7 milligrams per deciliter (mg/dL) for vegans and 118.5 mg/dL for omnivore participants.
It fell to 95.5 mg/dL for vegans (about a 13 percent decrease) and 116.1 mg/dL for omnivores at the end of the study. The optimal healthy LDL-C level is less than 100 mg/dL.
The vegan participants also showed a drop of about 20 percent in fasting insulin (a higher level of insulin 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, 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. Disease Prevention (CDC).
Further analysis of the participants’ biological ages (a measure of a person’s physical and metabolic age) found that at the end of the eight-week study, the twins who ate the vegan diet were biologically “slightly younger” than their omnivores. their counterparts, Gardner said in a video about the study.
“Based on these results and with longevity in mind, most of us would benefit from adopting a more plant-based diet,” he says.
Why would a vegan diet improve heart health?
Vegan participants did the three most important things to improve cardiovascular health, according to Gardner: they reduced their consumption of saturated fat, increased dietary fiber, and lost weight.
Most Americans consume about half the recommended amount of fiber, Gardner says.
RELATED: 11 High Fiber Foods to Add to Your Diet
A recommended dietary fiber intake of 14 grams per 1,000 calories of food is recommended. For example, with a baseline level of 2,000 calories (which is appropriate for some people, but not all), your daily dietary fiber intake should be 28 grams, according to the U.S. 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 International Journal of Environmental Research and Public Health.
Although the exact mechanism behind the benefits is not fully understood, it is suspected that saturated fats in meat and animal products may cause low-grade systemic inflammation that could contribute to heart disease.
Ready to try a Protein Flip?
If you’re not ready to fully embrace a vegan diet, you can still work on eating more vegetables and plant-based proteins and less meat by trying a “protein swap,” Gardner says.
“Most Americans think that the center of the plate is chicken, beef or pork and that the accompanying sides are grains and vegetables. The protein shift is to put the plants in the middle of the plate: the meat is no longer the centerpiece, but rather a flavoring or accompaniment,” he says.
One way to try it is with a bowl, which is popular in student cafeterias or supermarket hot bars. “You can build your own. So maybe there’s meat in there, but there could also be tempeh or tofu, and along with grains and vegetables,” he says. Switching protein doesn’t eliminate meat completely, but it can help reduce meat consumption, Gardner says.
