The Netflix Twin Study Documentary: A Longevity Dietitian’s Perspective

As a functional dietitian, I'm no stranger to the hype surrounding nutrition documentaries. When Netflix released You Are What You Eat, promising insights into plant-based eating, I was intrigued but cautious. Nutrition is incredibly complex, and past experiences have taught me to approach such documentaries with a critical eye.

One focal point of the film is the Stanford Twins Study, an 8-week trial comparing the effects of vegan and omnivore diets on cardiometabolic health. The premise is intriguing, but upon further inspection, several red flags arise.

The Study: Premise and Results

The study assigned 22 sets of twins to either an omnivore or vegan diet. The first four weeks consisted of provided meals, followed by four weeks of self-preparation. Bloodwork and weight measurements were taken before and after the study.

The vegan group showed a statistically significant decrease in LDL cholesterol and some weight loss compared to the omnivore group. However, the study also reported muscle mass loss and increased triglyceride levels in the vegan cohort, which raises concerns about long-term cardiovascular health. The vegan group also experienced a 25% drop in vitamin B12 levels and a reduction in HDL cholesterol, both known to elevate cardiovascular risks.

While LDL cholesterol decreased, its clinical significance may not be as impactful when paired with adverse effects on muscle mass, HDL, and triglycerides. Furthermore, the study's short duration complicates the interpretation of long-term benefits and potential risks. A decrease in calorie intake from the vegan diet may explain reductions in insulin, glucose, and weight, but without a broader context, these findings are less meaningful.

In essence, an 8-week study with such a small sample size makes it difficult to draw strong conclusions about the superiority of a vegan diet for long-term health. Claims in the documentary suggesting that veganism is universally better than omnivorous diets are unsubstantiated and potentially misleading. Long-term studies like the EPIC-Oxford studyshow that vegans may have lower rates of heart disease but also exhibit increased risks of fractures and deficiencies in vital nutrients (Appleby et al., 2016).

Misleading Data on Emissions

The documentary claims that agriculture contributes 31% of greenhouse gas emissions, compared to 14% from transportation. This is factually incorrect. Agriculture contributes around 14% to global emissions, and livestock accounts for 31% of that 14% (Gerber et al., 2013). Misrepresentation of environmental data undermines the documentary’s credibility, and we should be careful not to oversimplify the conversation about sustainability.

Nutrition: It’s Not That Simple

The film also promotes plant-based diets by suggesting extreme views, such as labeling cheese as "biologically addictive," a claim unsupported by scientific research. It neglects to mention the importance of Vitamin B12 supplementation for vegans and vegetarians, an essential factor for nervous system function and metabolic health. Research shows that Vitamin B12 deficiency is linked to cognitive decline, fatigue, and even cardiovascular disease (Allen, 2008).

Animal Agriculture: There Are Alternatives

The documentary portrays a stark contrast between eating factory-farmed meat and adopting a vegan lifestyle. While I agree that factory farming is unethical, it's important to highlight that not all animal agriculture is the same. Grass-fed, pasture-raised, antibiotic- and hormone-free meat offers a sustainable middle ground. Studies have shown that grass-fed beef has higher levels of omega-3 fatty acids and antioxidants, contributing to better health outcomes (Daley et al., 2010).

We also need to consider meat quality when interpreting study results. If the omnivorous diet in the Stanford study included highly processed meats, the results would differ greatly from a diet of high-quality, ethically sourced meat.

Conflicts of Interest

Another issue is the funding behind the Stanford Twins Study. The study was funded, in part, by individuals with ties to the vegan advocacy movement and plant-based food companies like Beyond Meat. While this doesn’t invalidate the results, it raises questions about potential bias. Research shows that industry-funded studies are more likely to report favorable outcomes, which can influence public perception (Lesser et al., 2007).

Shortcomings of the Study

The study’s short duration—just 8 weeks—is a major limitation. Longer-term studies are needed to understand the sustainability and practicality of any dietary intervention. Additionally, most participants were women, and the self-prepared meals during the last four weeks lack control, introducing variability that could affect results. Longitudinal studies like the Adventist Health Studies (Fraser, 2003) provide better insight into the long-term effects of plant-based diets, showing both benefits and risks depending on individual adherence and nutritional balance.

Correlation vs. Causation

One of the most significant flaws in the documentary is its failure to distinguish between correlation and causation. While vegans may exhibit certain health benefits, this does not mean veganism directly causes those benefits. Vegans often lead healthier lifestyles overall, including exercise, stress management, and avoiding processed foods, which could account for the observed health advantages. Nutrition research is multifaceted, and isolating diet from other factors is difficult.

There Is No One-Size-Fits-All Approach

One of the biggest takeaways from my journey as a dietitian is that there is no universal diet. Each individual has unique needs based on their genetics, lifestyle, and environment.

For some, a vegan diet may lead to optimal health, but for others, incorporating animal products in a balanced and ethical way may be more beneficial.

My personal experience aligns with this. After a year of veganism, I transitioned away from it and saw transformative health improvements.

I realized that bio-individuality is key to optimal health, and no single diet works for everyone.

Make Your Own Decision - Learn from you Bio-Individuality

Documentaries like You Are What You Eat can spark important conversations, but they need to be approached with critical thinking. Look beyond the headlines, investigate the funding, and carefully consider the evidence. Nutrition is a complex science, and no documentary can capture all the nuances.

By promoting a balanced understanding and education of nutrition, gut health and longevity science and encouraging open dialogue about the limitations of research, we can foster a more thoughtful approach to health and longevity.

Schedule an evaluation call to start your journey to bio-individuality with Gut-Brain Method

References:

• Appleby, P. N., Crowe, F. L., Bradbury, K. E., Travis, R. C., & Key, T. J. (2016). Mortality in vegetarians and comparable nonvegetarians in the United Kingdom. American Journal of Clinical Nutrition, 103(1), 218-230.

• Gerber, P. J., Steinfeld, H., Henderson, B., et al. (2013). Tackling climate change through livestock: A global assessment of emissions and mitigation opportunities. Food and Agriculture Organization of the United Nations (FAO).

• Allen, L. H. (2008). Causes of vitamin B12 and folate deficiency. Food and Nutrition Bulletin, 29(2_suppl1), S20-S34.

• Daley, C. A., Abbott, A., Doyle, P. S., Nader, G. A., & Larson, S. (2010). A review of fatty acid profiles and antioxidant content in grass-fed and grain-fed beef. Nutrition Journal, 9, 10.

• Fraser, G. E. (2003). Diet, life expectancy, and chronic disease: Studies of Seventh-Day Adventists and other vegetarians. American Journal of Clinical Nutrition, 78(3), 529S-532S.

• Lesser, L. I., Ebbeling, C. B., Goozner, M., Wypij, D., & Ludwig, D. S. (2007). Relationship between funding source and conclusion among nutrition-related scientific articles. PLoS Medicine, 4(1), e5.