Identical twins Carolyn, left, and Rosalyn in the documentary “You Are What You Eat: A Twin Experiment.” Courtesy of Netflix

My first hint at the impact of the new Netflix documentary “You Are What You Eat: A Twin Experiment” happened just after the episodes dropped on Jan. 1. That’s when my aunt told me she’d watched the series and was now eating mostly vegan. Next, a friend emailed asking for cookbook recommendations, saying she’d recently watched the film series and was looking to eat more plant-based meals. Then I started seeing the film mentioned all over social media.

When I asked my Facebook friends if they were watching, the post kicked up almost 100 comments, including “It is life changing,” “Started my plant based journey this week,” and “I watched a bunch of it and now for the first time have been dipping my toes into a significantly more plant-based diet.”

USA Today reports the Netflix series “has everyone buzzing,” and once I watched it I understood why. The film documents how eating vegan food can make you younger.

Directed by Academy Award-winning filmmaker Louie Psihoyos, the film highlights an unusual medical study conducted by Stanford University. It makes compelling watching and is rousing viewers from their food routines. No wonder, the Stanford provides an example – within just four weeks – of why DNA is not destiny.

After Puddy Holmes of Windham watched the documentary, she tossed all the food in her kitchen and restocked with whole, plant-based foods. Four weeks and added exercise later, she’d already shed 10 pounds and is feeling much better. “Emotionally, I’m happier, and I feel like I have more clarity,” Holmes told me by phone. “I’ll get my cholesterol tested in March. My goal is to get off my statin and my thyroid medication.”

If she does, she says she’ll save money at the drug store and earn a discount on her health insurance. “I started reading labels and was shocked at some of the stuff I was putting into my body,” she said.


Psihoyos won an Oscar for his 2009 documentary “The Cove” and has directed other critically acclaimed films including “Racing Extinction” and “The Game Changers.” He said that the study’s “most surprising finding was how quickly the human body responds to eating a healthy diet. With a plant-based diet you have to get comfortable eating slightly more food. It’s counter-intuitive, but by eating more plants, you lose more weight.”

Psihoyos sees collective economic advantages of plant-based meals, too, telling me via email that “When your neighbor eats the Standard American Diet, which includes a lot of animal products and processed food, all of our insurance premiums go up.”

Holmes learned about the film from her doctor, Craig Brett, a cardiologist with Northern Light Mercy Cardiovascular Care in Portland. Dr. Brett says he talks about nutrition with all his patients, and if they show interest in changing their diet, he recommends films such as “You Are What You Eat” and the 2011 documentary “Forks Over Knives.”

“The plant-based diet has been well studied and has convincingly been shown to be effective in treating these disease states that put people at risk for heart attack and stroke,” Brett wrote me in an email. “This was poignantly demonstrated in a Stanford Medicine study.”

Twins Michael, left, and Charlie with vegan cheesemaker Miyoko Schinner in “You Are What You Eat: A Twin Experiment.” Courtesy of Netflix

Stanford professor Christopher Gardner led the study, which took 22 pairs of healthy identical twins and randomly assigned one to eat nutritionally balanced plant-based meals and the other to eat nutritionally balanced animal-based meals. Since the twins share identical DNA, the researchers were able to rule out gene variation and isolate the health effects of lifestyle choices. For eight weeks, both groups of twins worked with exercise trainers and dietitians and were observed, weighed, measured and analyzed. For the first four weeks, prepared meals were delivered to study participants. During the final four weeks, they had to prepare their own meals.

Spoiler alert: The study found that after just four weeks, participants assigned to eat the vegan meals significantly lowered their insulin levels, body weight and low-density lipoprotein cholesterol. The vegan twins also significantly reduced their visceral fat, which is fat that accumulates around internal organs and is associated with chronic diseases. All participants showed improvements, but they were most dramatic for those eating plant-based diets.


The study also measured the participants’ epigenomes, a part of our DNA that determines the way genes act. While genes are fixed, epigenomes change based on our lifestyles and environment. The study found that by the end of eight weeks, the twins eating the vegan meals became biologically younger than the twins eating animal-based meals due to the lengthening of their teleomeres, which is a section of our DNA that shortens as we age.

“How different were the twins?” Psihoyos asked me, rhetorically. “Put it this way, the twins were no longer identical. All the plant-based twins were biologically younger than their meat-eating counterparts. Nobody expected that, certainly not the scientists.”

The film follows four sets of participating twins over the course of the study and juxtaposes this with interviews with doctors, public health advocates and food system influencers, who sketch a fuller picture of the systemic challenges Americans face following a vegan diet. Author and doctor Michael Greger talks about conflicts of interest within the healthcare industry, arguing that pharmaceutical companies have a vested interest in confusing the medical community about the role of food in health. Nutrition professor and writer Marion Nestle discusses how the livestock lobby has worked tirelessly to make sure the national nutrition guidelines use vague, hard-to-follow statements about reducing saturated fat rather than simply saying Americans need to eat less meat.

Miyoko’s Creamery founder Miyoko Schinner talks about how mammal milk chemically hooks us because it’s meant to keep infants, whether calves or humans, coming back for more so they can bulk up fast. The film then showcases the award-winning, plant-based cheeses made by Miyoko’s Creamery. (From 2012 to 2015, Schinner co-hosted the Maine-produced PBS cooking show Vegan Mashup, )

The film also spotlights the decision by the Michelin-starred restaurant Eleven Madison Park, in Manhattan, to pivot to an all-vegan menu as the pandemic was beginning to wane. Renowned Chef Daniel Humm talks about the backlash from the press and the hateful messages from meat suppliers the change provoked. He was surprised but not deterred.

“Plant-based is the future,” Humm says in the film. “This isn’t a trend.”

Avery Yale Kamila is a food writer who lives in Portland. She can be reached at

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