Following a vegan diet for eight weeks is associated with reduced estimates of biological age based on levels of DNA methylation, a type of chemical modification of DNA (known as an epigenetic modification) that alters gene expression but not the DNA itself.
The benefits of a vegan diet
Previous research has reported that increased levels of DNA methylation are associated with aging. The new findings, based on a small, randomized, controlled trial of 21 pairs of adult identical twins, are published in BMC Medicine .
Varun Dwaraka, Christopher Gardner, and colleagues studied the molecular effects of a short-term vegan diet by asking half of each pair of twins to follow an omnivorous diet for eight weeks, which included between 170 and 225 grams of meat, one egg, and one and a half servings of dairy products per day, and the other half to follow a vegan diet for the same period of time.
The sample was 77% female (32), and participants were on average 40 years old and had an average body mass index of 26 kilograms per square meter. For the first four weeks of the study, participants ate meals that had been prepared for them, and for the second four weeks, participants ate meals that they had prepared themselves, after receiving nutrition lessons from health educators.
Vegan buddha bowl dinner food table. Healthy food. Healthy vegan lunch bowl. Fritter with lentils and radish, avocado, carrot salad. Flat lay. Top view
The authors studied the impact of diet on DNA methylation levels by analyzing blood samples collected from participants at baseline, week four, and week eight of the study. They used DNA methylation levels to infer the biological ages of participants and their organ systems.
By the end of the study, the authors observed decreases in biological age estimates, known as epigenetic aging clocks, in participants who ate a vegan diet, but not in those who ate an omnivorous diet. They also observed decreases in the age of the heart, hormones, liver, and inflammatory and metabolic systems of participants who ate a vegan diet, but not an omnivorous diet, for eight weeks.
The authors caution that it is unclear to what extent the differences observed among participants who followed different diets can be attributed to their dietary compositions. They note that participants who followed a vegan diet lost two pounds more on average than those who followed an omnivorous diet because of differences in the caloric content of the meals provided during the first four weeks of the study.
They suggest that these weight loss variations may have contributed to the observed differences in epigenetic age between the two groups. Further research is needed to investigate the relationship between dietary composition, weight, and aging, as well as the long-term effects of vegan diets, they add.
Twin study suggests vegan diet improves cardiovascular health
In a study of 22 pairs of identical twins, Stanford Medicine researchers and their colleagues found that a vegan diet improved cardiovascular health in as little as eight weeks.
While it is well known that eating less meat improves cardiovascular health, dietary studies are often hampered by factors such as genetic differences, upbringing, and lifestyle choices. By studying identical twins, however, researchers were able to control for genetics and limit other factors, because the twins grew up in the same families and reported similar lifestyles.
“Not only did this study provide a groundbreaking way to say that a vegan diet is healthier than a conventional omnivorous diet, but the twins were also a blast to work with,” said Christopher Gardner, Ph.D., the Rehnborg Farquhar Professor and professor of medicine. “They dressed alike, talked alike, and had a banter with each other that you could only have if you spent an inordinate amount of time together.”
The study was published in JAMA Network Open . Gardner is the lead author. The study was co-authored by Matthew Landry, Ph.D., a former Stanford Prevention Research Center postdoctoral fellow now at the University of California, Irvine, and Catherine Ward, Ph.D., a postdoctoral fellow at the center.
The trial, conducted from May to July 2022, involved 22 pairs of identical twins for a total of 44 participants. The study authors selected healthy participants without cardiovascular disease from the Stanford Twin Registry, a database of fraternal and identical twins who agreed to participate in research studies, and matched one twin from each pair to a vegan or omnivorous diet.
Both diets were healthy, rich in vegetables, legumes, fruits, and whole grains, and free of refined sugars and starches. The vegan diet was entirely plant-based, including no meat or animal products such as eggs or milk. The omnivorous diet included chicken, fish, eggs, cheese, dairy, and other animal-based foods.
During the first four weeks, a meal service delivered 21 meals per week: seven breakfasts, lunches, and dinners. For the remaining four weeks, participants prepared their own meals.
A registered dietitian, or “diet whisperer,” according to Gardner, was available to offer advice and answer questions about diets throughout the study. Participants were interviewed about their dietary intake and kept a log of the food they ate.
Forty-three participants completed the study, which Gardner says demonstrates how achievable it is to learn how to prepare a healthy diet in four weeks.
“Our study used a generalizable diet that is accessible to anyone, because 21 of 22 vegans followed the diet,” said Gardner, a professor at the Stanford Prevention Research Center. “This suggests that anyone who chooses a vegan diet can improve their long-term health in two months, with the greatest change seen in the first month.”
The authors found the greatest improvement in the first four weeks of diet change. Participants on a vegan diet had significantly lower levels of low-density lipoprotein cholesterol (LDL-C), insulin, and body weight, all associated with better cardiovascular health, compared to omnivorous participants.
At three different times—at the start of the trial, at four weeks, and at eight weeks—researchers weighed participants and drew blood. The average baseline LDL-C level for vegans was 110.7 mg/dL and 118.5 mg/dL for omnivorous participants; it dropped to 95.5 for vegans and 116.1 for omnivores at the end of the study. The optimal healthy LDL-C level is less than 100.
Because participants already had healthy LDL-C levels, there was less room for improvement, Gardner said, hypothesizing that participants with higher baseline levels would show greater changes.
Vegan participants also showed about a 20 percent drop in fasting insulin — higher insulin levels are a risk factor for developing diabetes. Vegans also lost an average of 4.2 pounds more than omnivores.
“Based on these findings and with longevity in mind, most of us would benefit from adopting a more plant-based diet,” Gardner said.
According to Gardner, the vegan participants (and to some extent the omnivores) did the three most important things for improving cardiovascular health: they reduced saturated fat, increased their dietary fiber intake, and lost weight.
Gardner points out that while most people probably won’t go vegan, a push in the plant-based direction could improve health. “A vegan diet may confer additional benefits such as increased gut bacteria and reduced telomere loss, which slows the body’s aging,” Gardner said.
“What’s more important than going strictly vegan is including more plant-based foods in your diet,” said Gardner, who has been “mostly vegan” for the past 40 years. “Fortunately, enjoying multicultural vegan foods like Indian masalas, Asian stir-fries, and African lentil dishes can be a great first step.”
Gardner 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.
Vegan diet rich in legumes is useful for weight loss
A vegan diet improves diet quality, leading to weight loss and improved insulin sensitivity, according to a new study from the Physicians Committee for Responsible Medicine published in the Journal of the Academy of Nutrition and Dietetics. Weight loss was most strongly associated with increased intake of legumes and decreased intake of meat, fish, and poultry.
“Our research shows that the best way to improve your health is to improve the quality of the foods you eat,” says Hana Kahleova, MD, Ph.D., director of clinical research at the Physicians Committee and a co-author of the study. “That means avoiding animal products and eating a vegan diet rich in fruits, vegetables, grains, and beans.”
Participants in the 16-week study included 244 overweight adults who were randomly assigned to make no dietary changes or to follow a low-fat, calorie-restricted vegan diet consisting of vegetables, grains, legumes, and fruits. Researchers monitored diet quality, body weight, fat mass, and insulin sensitivity. The final data analysis included 219 participants who completed the entire study and submitted their final dietary records.
Improvements in insulin sensitivity were also seen in the vegan group.
The vegan group’s diet quality, as measured by the Alternative Healthy Eating Index-2010 (AHEI) score, also increased by an average of 6 points, in contrast to no significant change in the group that made no dietary changes. The AHEI was developed by researchers at the Harvard School of Public Health to identify dietary patterns associated with a lower risk of chronic disease.
The index is made up of foods that are eaten more often, such as fruits and vegetables, and those that are eaten less often, such as red and processed meat. The higher the AHEI score, the lower the risk of chronic disease.