Netflix's "You Are What You Eat: A Twin Experiment" is a 2024 American documentary series that explores the impact of different diets on the body. Directed by Louie Psihoyos, the series follows an 8-week study conducted by Stanford University, where 22 sets of genetically identical twins were placed on opposing diets: one omnivorous and one vegan. The show chronicles the experiences of four pairs of identical twins who participated in an eight-week study with Stanford Medicine researchers as they compared the impacts of a vegan diet with an omnivore diet. This article delves into the details of the study, the documentary, and the broader implications of their findings.
The Stanford Twin Study: A Closer Look
The core of the documentary is an 8-week randomized clinical trial, published in JAMA Network Open in November 2023, titled "Cardiometabolic Effects of Omnivorous vs Vegan Diets in Identical Twins." Led by Christopher Gardner, the Rehnborg Farquhar Professor of Medicine at the Stanford Prevention Research Center, the study aimed to assess the health impacts of vegan and omnivorous diets on genetically identical individuals.
Methodology
The study involved 22 pairs of healthy, adult identical twins. One twin from each pair was assigned to a "healthy" vegan diet, while the other followed a "healthy" omnivorous diet. During the first four weeks, all meals were provided to the participants. In the subsequent four weeks, the participants prepared their own meals, guided by a registered dietitian, adhering to their assigned dietary guidelines.
Key Findings
The study revealed several significant differences between the two groups:
- LDL Cholesterol: The vegan group experienced a substantial reduction in LDL ("bad") cholesterol levels, with noticeable changes as early as four weeks.
- Insulin Levels: Fasting insulin levels decreased in the vegan group, indicating improved insulin sensitivity, a critical marker for diabetes risk. The omnivorous group did not exhibit significant changes in insulin levels.
- Weight Loss: Both groups lost weight during the study, but the vegan group experienced greater weight loss overall.
However, some less favorable outcomes were observed in the vegan group:
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- HDL Cholesterol: The vegan group saw a decrease in HDL ("good") cholesterol, which plays a cardioprotective role.
- Triglycerides: Triglyceride levels tended to increase in the vegan group, an undesirable change as elevated triglycerides can increase the risk of heart disease.
- Muscle Mass: Body composition reports of the four pairs of twins in the documentary showed muscle loss in all of the vegan diet group participants.
Additional Considerations
Several aspects of the study design and execution warrant further consideration:
- Dietary Recommendations: The vegan group was instructed to consume 6 servings of vegetables and 3 servings of fruit daily, while the omnivorous group was instructed to consume 3 servings of vegetables and 2 servings of fruit every day. This significant difference in fruit and vegetable intake could have influenced the results, as higher intakes of fruits and vegetables are associated with reduced LDL cholesterol and a lower risk of coronary heart disease.
- Meat Alternative Intake: The omnivorous participants decreased their intake of meat alternatives (e.g., nut butters, nuts/seeds, pulses) from baseline during both the food delivery and self-provided phases.
- Blinding: The study was not blinded, meaning that the researchers and personal trainers were aware of the participants' diets. This lack of blinding could introduce bias into the evaluation and reporting of results.
- Funding: The study was funded by the Vogt Foundation, which has previously supported pro-vegan documentaries. One of the researchers, Christopher Gardner, has also received sponsorship and payment from Beyond Meat.
Netflix Documentary: "You Are What You Eat: A Twin Experiment"
The Netflix series brings the Stanford twin study to a broader audience, showcasing the experiences of the participants and highlighting the potential health benefits of a vegan diet.
Focus on Twin Pairs
The documentary focuses on four sets of twins with diverse backgrounds and motivations:
- Carolyn (vegan) and Rosalyn (omnivore): These twins participated to increase Filipino representation in scientific studies. After the study, they both returned to an omnivorous diet but now include more plant-based meals.
- Pam (vegan) and Wendy (omnivore): South African chefs who run a catering company. After the study, they returned to an omnivorous diet but reduced their intake of meat and cheese.
- John (vegan) and Jevon (omnivore): Nursing students who also like to work out. After the study, they both returned to an omnivorous diet but cut out most red meat from their diet.
- Michael (omnivore) and Charlie (vegan): Owners of a cheese business, known as "The Cheese Twins." Prior to the study, Michael was a pescatarian, and Charlie an omnivore.
Documentary Style and Potential Biases
While the documentary presents compelling visuals and personal stories, some critics argue that it exhibits a pro-vegan bias. Claims have been made that the language used in the series is likely to induce food fear, and there are comments like “cheese is biologically addictive,” even though research has shown that food addiction is NOT a real thing. The series has been described as propaganda for the vegan diet where we only hear from vegan advocates. The context of the food industry etc especially the bacteria in some meat was quite interesting, but again it was quite heavily biased towards veganism, not showing one drawback of a full plant based diet and it felt like they were trying to do 2 things in one - the actual study and a documentary about the bad meat industry. This is likely to make someone fearful of specific foods like cheese or meat, and exclude them from the diet without further knowledge or education on the matter. Putting negative connotations on specific foods is also likely to make you feel guilty for what you’re eating.
Additional Study Markers
The documentary included additional "study" markers that weren’t included in the JAMA study: the gut microbiome, telomere length (connected to longevity) and genital blood flow while watching pornography, (which, by the way, was only discussed in 2 sets of twins and really didn’t tell us anything about the health or sexual health of the participants).
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Implications and Considerations
The Stanford twin study and the "You Are What You Eat" documentary raise important questions about the optimal diet for human health. While the study suggests that a vegan diet may offer certain advantages, such as lower LDL cholesterol and improved insulin sensitivity, it is crucial to consider the following:
- Individual Needs: Dietary needs vary based on individual factors such as genetics, activity level, and health status.
- Nutrient Deficiencies: Vegan diets can be deficient in certain nutrients, such as vitamin B12, iron, and omega-3 fatty acids, requiring careful planning and supplementation.
- Sustainability: The long-term sustainability of any diet depends on individual preferences, cultural factors, and accessibility to healthy foods.
- The Importance of Plant-Based Eating: The study suggests that cardiovascular benefits can be achieved with modest reductions in animal foods and increases in healthy plant-based foods.
Expert Opinions
Christopher Gardner says having his research featured in the Netflix food series You Are What You Eat has been one of the more impactful things he’s done in more than 30 years at Stanford. Ever since the show’s Jan. 1 release, Gardner’s inbox has been packed with feedback from strangers, colleagues, and others. Gardner’s own sister told him that after watching the documentary, she may try eating more plant-based meals.
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