In the last few years, multiple studies have suggested that a whole food, plant-based diet is one of the best ways to eat for our health. But new research, published in November 2023, which focused on the diets of identical twins, might just be the closest to definitive proof we’ve seen so far. 

By studying 22 sets of identical twins, Stanford Medicine researchers were able to control for genetic and lifestyle factors, and simply focus on the health benefits of diet. In the study, which took place from May to July 2022, one twin followed a vegetable-rich omnivorous diet, with foods like chicken, fish, and eggs, while the other followed a vegetable-rich plant-based diet.

The researchers found that in the first four weeks, those on a plant-based diet had lower levels of LDL cholesterol and insulin, and they lost weight. All of these factors are associated with a lower risk of heart disease, which is the leading cause of death globally. This was likely because the twins on a plant-based diet were naturally eating more fiber and less saturated fat.

In January 2024, the research was the main subject of the Netflix documentary You Are What You Eat: A Twin Experiment, which followed some of the twins and their journeys, and also examined the history of the food system, the Standard American Diet, and the ethical and environmental impact of the way we produce meat and dairy. 


All of the twins started the study with relatively healthy LDL cholesterol levels, but the study still showed significant improvement. During the research, the average baseline LDL cholesterol level for vegans was 110.7 mg/dL and 118.5 mg/dL for omnivores. By the end, vegans had dropped to 95.5, while omnivores had reached 116.1.

For context, for those with no health issues, cholesterol between 100 and 129 isn’t generally considered concerning, but below 100 is the optimal LDL cholesterol score.

The results indicate that a plant-based diet could make a difference for those with concerningly high cholesterol levels in a matter of weeks.

Christopher Gardner, PhD, the study’s senior author, claimed that the research was a “groundbreaking way to assert that a vegan diet is healthier than the conventional diet.” He added that out of the 22 vegans in the study, 21 have carried on with the plant-based lifestyle.

“[The research] suggests that anyone who chooses a vegan diet can improve their long-term health in two months, with the most change seen in the first month,” he continued. 

Vegan food and heart health

The new study builds on existing research that links plant-based foods with improved heart health. While the Standford researchers focused on a whole foods plant-based diet, with contains very few processed foods, previous studies have also suggested that even switching from animal meat to vegan meat could have a positive impact on health.

For example, another recent Stanford Medicine study, also led by Gardner, compared red meat consumption with plant-based meat consumption in a group of 30 people. “There’s been this sort of backlash against these new meat alternatives,” he said in a statement. “The question is, if you’re adding sodium and coconut oil, which is high in saturated fat, and using processed ingredients, is the product still actually healthy?”

The study found that those who consumed at least two servings of plant-based meat a week had lower levels of trimethylamine N-oxide (TMAO). Those who only ate red meat had higher levels. Emerging evidence has linked higher TMAO levels with a potential increased risk of cardiovascular disease. 

The study also, again, found a modest drop in weight and LDL cholesterol levels for those who ate more plant-based meat. 

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Can vegan food lower disease risk in general?

A diet rich in plant-based foods hasn’t just been linked with a decreased risk of heart disease, it’s also associated with a lower risk of certain types of cancer (read more on that here), as well as type 2 diabetes, dementia, kidney disease, and even depression.

In July, one study suggested that eating a handful of nuts every day could lower the risk of depression by 17 percent.

Another Netflix series called Live to 100: Secrets of the Blue Zones, also revealed that in the five centenarian hotspots around the world (known as the Blue Zones), one of the lifestyle habits people have in common is a diet rich in plant-based whole foods. One food, in particular, however, stood out: beans. 

“Beans are an amazing food and they are closely related to longevity in those who eat them regularly,” Anna Herby, DHSc, RD, CDE Nutrition Education Specialist for the Physicians Committee for Responsible Medicine (PCRM), told VegNews.

“The fiber in beans helps to usher out extra cholesterol if blood levels are high, and then, again through its impact on the gut microbiome, leads to reduced cholesterol production in the liver,” she added. “Beans are so filling and can help you to feel more satisfied with a lower amount of calories, leading to better weight management in those who eat them regularly. With all these health benefits, it’s no wonder those who eat them live longer, healthier lives.”

Gardner agrees. “Based on these results and thinking about longevity, most of us would benefit from going to a more plant-based diet,” he said, speaking about the twin study.

For more on vegan food and health, read:
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