Are You What You Eat? A Dive into Netflix’s 'A Twin Experiment’

Written by: Natalie Louise Burrows


Healf Journal

You’ve undoubtedly seen the new release on Netflix since its launch on January 1st. What was a Stanford University science experiment is now a 4-part docu-film released in time for Veganuary.

Ignoring the cringe-worthy connection to the diet-culture push after Christmas, is the information shared in this documentary something we should implement? Should we all be moving towards a plant-based diet following the results of this health experiment?

Lets review what was covered on-screen and analyse the research that the documentary chose not to show.

Written by Natalie Louise Burrows - registered Nutritional Therapist and Clinic Director of Integral Wellness, specialising in cardiometabolic health.

Before the cameras started rolling

On November 30, 2023, an 8-week clinical trial where 44 participants (22 pairs of twins) undertook a diet study was published. One twin ate a healthy plant-based (vegan) diet and the other ate a healthy omnivore diet for the duration with specific health markers measured before and after.

For the initial four weeks, participants received vacuum-packed ready meals, and for the final four weeks, they prepared meals according to their designated diet.

While the use of processed and non-fresh foods raises certain concerns, it is important to appreciate the challenges inherent in controlling participant intake during a study where the outcome is the measured variable. So let’s not dwell on this, for now.

For the documentary, just four of the 22 twins were included in the filming and a dedicated team provided commentary on the approach, findings, and additional insights. However, what immediately struck me was that the team consistedentirely of plant-based advocates.

Where are the omnivore voices? This notable absence prompts concern for an objective narrative and leans toward potential bias in the documentary. All before I have even hit play!

Further scrutiny reveals that Christopher Gardener, the lead commentator and a contributing author of the study, has received funding from Beyond Meat, a plant-based food company. This financial connection, along with the study's funding from the Vogt Foundation - a promoter of plant-based products - is a strong conflict of interest. Although conflicts of interest and funding don’t make a study unfounded it does mean we have to look more carefully at the data.

The climate change detour

The purpose of the study was to examine ‘the cardiometabolic effects of a healthy plant-based (vegan) vs a healthy omnivorous diet among identical twins during an 8-week intervention’. Yet somehow across the series, it takes an unexpected turn and we detour into a climate change documentary with stories and stats covering carbon emissions, animal welfare, and antibiotic resistance.

While these topics are important, their inclusion in a documentary centered around a dietary study diverts attention from the stated purpose and angles the viewer towards a different aim. The absence of nuanced language leads to a generalisation of all meat consumption without considering the complexities of various farming practices, processing techniques, cooking methods etc.

There is a positive side to this in that it delivered insights that help inform decisions about food choices;

  • Highlighting that chicken farming of ‘barn eggs’ is not comparable to chickens having the freedom to roam in fields.
  • Exposing the use of low-level antibiotics in industrial farming and its impact on antibiotic resistance in humans (thankfully not a concern here in the UK as it is in the US).
  • Calling attention to supermarket labelling and that a limited understanding of where food comes from can lead you to purchase something that isn’t what you think it is (e.g. dyed salmon)

This type of knowledge-share encourages people to get closer to their food source and reconnect with nature, not brands.

However the climate change diversion went as far as to include a story of a lawsuit case between a community and a hog farmer who was spraying his and adjoining lands with hog faeces. That sounds horrendous but what does this have to do with a study between two different dietary preferences?

Language matters

Within the first 25 minutes of the documentary, viewers are hit with statements such as “dairy and meat are not needed for protein.” This is paired with allegations that the dairy and meat industry manipulate studies and ads to fabricate a need for these foods.

Beyond broad claims that lack context and leave a lot to the viewer’s interpretation, influenced by the carefully chosen visual images on screen, it’s interesting that in a study and documentary with clear conflicts of interest, they opt to criticise a competing industry for a similar offence.

The narrative persists with bold statements, yet instead of explaining that highly processed meat and certain cooking methods are harmful to our health, the documentary generalises, by portraying meat and processed foods as the main causes of heart disease and type 2 diabetes. A more balanced approach, distinguishing between quality of meat and highlighting the importance of avoiding fried and fast foods, could have better educated viewers on specific aspects of their diet that could benefit from changes.

Perhaps this would have been too conflicting for the fourth episode when the promotion of plant-based meat alternatives ramps up. In this final segment, we hear from four founders of plant-based food companies who are all producing ultra-processed foods to replace meat products. These contain protein sourced from soy, mushroom, pea or wheat, fortified with vitamins and minerals and added flavourings, starches, and thickeners, including the likes of maltodextrin which can cause alterations in gut bacteria and blood sugar imbalances.

However, a beef burger can be made from 100% beef. I’ll let you decide which one you’d like to eat. At the end of the day, choice is a blessing we are entitled to when it comes to food.

Show me the results

The part everyone wants to know about - which diet is healthier?

When the study was published the headlines sparked widespread discussion as they touted the superiority of the vegan diet for cardiometabolic health.

But when we look at the data and what happened across 8 weeks (a short time frame) in 44 people (a small participant number) there’s a lot more to unpick than the headlines and documentary suggest.

The study examines key markers such as body weight, body fat, muscle mass, LDL-cholesterol, and TMAO (a marker of inflammation).

While the vegan diet group shows slightly more weight loss, weight is not a stand-alone health marker and the calorie intake, which is less than those on the omnivore diet, could potentially explain this difference.

Interestingly, only one participant on the vegan diet expressed a commitment to ‘closely follow all recommendations’ after the study ended. This indicates potential challenges and lack of satisfaction with the plant-based approach; the documentary’s twins noted feeling full due to the high carbohydrate content of the vegan diet.

The documentary overlooked the challenge of protein intake on a vegan diet, evident in the lack of muscle mass growth. On review of the DEXA scan results, it shows muscle mass decreased in the twins following the vegan diet - except for a young, athletically fit male. Yet the documentary gloss over this negative health outcome. 

What was highlighted was the change in LDL (so-called ‘bad’ cholesterol) in the vegan diet compared to the omnivore diet. However, for cardiovascular risk this is a little short-sighted. LDL is not the main associated marker with heart disease, and is not a risk factor for women. It is considered a risk factor for men but with only 10 of the 44 participants being male this seems to be ignored and the results sensationalised. There are other risk factors to consider to make a full picture of someone's health status and cardiovascular risk including fibrinogen, apolipoprotein-B, triglycerides and HDL (‘good’ cholesterol).

This is data the documentary decides not to include. If we review the results of triglycerides and HDL-cholesterol, these shift in the wrong direction. In the vegan diet HDL-cholesterol decreased and triglycerides increased, affecting the HDL:TG ratio. This is an independent risk factor for cardiovascular disease for both men and women. Cholesterol is about the whole picture and a marked change in LDL contradicted by HDL and TG deserves a conversation.

A few more things that were missing from the documentary; the vegan diet reduced insulin which is a positive outcome. It also saw a reduction in B12; a key nutrient missing from a vegan diet and an ideal opportunity to educate around this important topic for plant-based eaters.

Finally, TMAO (trimethylamine n-oxide), was highlighted in the documentary results as the omnivores increased from baseline and the vegan diet participants decreased which paints the conclusion that being an omnivore is more inflammatory. Or does it? When reading the research paper this result was stated to be ‘nonsignificant’.

Reporting on the stats that work in favour of a specific diet and ignoring those that don’t is another example of sensationalising

Unpacking the documentary and research - what are the takeaways?

I’m going to keep it simple and wrap this up. There is no winner.

This study and documentary succeeds (I hope) in drawing attention to the rapid impact dietary changes can have on certain health markers. However, the failure lies in oversimplifying the complex landscape of nutrition into a binary choice between vegan and omnivorous diets (shock horror, nutrition requires more nuance).

The documentary's inclusion of broader topics like climate change, animal welfare, and community lawsuits, while important, diverts attention from the dietary study's primary objectives and brings suspicion to the narrative. Alongside the lack of diverse perspectives in the commentary team, coupled with potential conflicts of interest, it undermines any claim of unbias.

Ultimately, I hope everyone is encouraged to adopt a more nuanced approach to nutrition. It's not about choosing between vegan and omnivorous diets in the search of superiority. But rather emphasising good-quality, locally sourced, seasonal foods and raising awareness about the pitfalls of processed and fast food consumption - both meat-based and plant-based.

Addressing the broader debate surrounding climate change and meat consumption requires a separate discussion but for now, supporting regenerative farmers is a more environmentally conscious and healthful choice. Concerns about excessive meat consumption are countered by the staggering amount of meat wasted annually. There is a clear need for mindful consumption and a reduction in production.

However blame doesn't lie with meat itself but rather with industrial farming practices, food processing, and poor cooking methods.

As for health problems, in my experience and from further research, the focus remains on excessive sugar consumption, a pervasive issue contributing to rising rates of obesity and type 2 diabetes.

So, as a takeaway;

  • Increase your intake of vegetables, plants and fibre
  • Reduce ultra-processed and processed foods
  • Swap to regeneratively farmed animal products
  • Get closer and more connected to your food; where it comes from, its quality, and its nutritional benefits.


This article is for informational purposes only, even if and regardless of whether it features the advice of physicians and medical practitioners. This article is not, nor is it intended to be, a substitute for professional medical advice, diagnosis, or treatment and should never be relied upon for specific medical advice. The views expressed in this article are the views of the expert and do not necessarily represent the views of Healf