Stanford Vegan Twin Study Deep Dive
There’s a new nutrition study that’s set to be released tomorrow (January 1st) as a Netflix Documentary.
Because this study is stirring up SO MUCH controversy, I wanted to take this newsletter to help you read between the lines before you sit down to watch.
I encourage you to read all the way through to the end (and to keep an open mind) for some insights on the link between diet, health, and our greater environmental impact.
Let’s get right into it, shall we?
The study: Cardiometabolic Effects of Omnivorous vs Vegan Diets in Identical Twins A Randomized Clinical Trial, comes out of Stanford University.
What was the objective? To determine which diet was best for optimal health: a vegan vs. omnivore diet.
What set this study apart? Researchers used 22 sets of healthy identical twins (one twin was randomly assigned to the vegan diet, and the other was assigned to the omnivore diet). Because twins share the same DNA, this helped eliminate the genetic variability that often interferes with nutrition research.
How long did the study last? 8 weeks
How did the study go down? In 2 phases.
Phase 1 (weeks 1-4): All meals were provided via a meal delivery service to familiarize twins with their assigned diet.
Phase 2 (weeks 4-8): Participants were expected to understand their assigned diet and instructed to purchase, prepare, and consume foods on said diet.
What did the participants eat?
Results
What was the main research outcome measured?: LDL cholesterol (aka the “bad” cholesterol), because high levels are associated with heart disease – we’ll talk about why this is outdated in a second)
How did each dietary intervention affect energy and macronutrient intake?
How did a vegan diet change LDL (the primary outcome)?
Vegan twins experienced ↓ 13.9 mg/dL decreases in LDL.
Other Results…..
Vegan twins’ fasting insulin ↓ 2.9 mIU/mL
Vegan twins’ body weight: ↓ 1.9 kg
Vegan twins experienced reductions in:
HDL cholesterol (↓3.6 mg/dL) *this is our good cholesterol*
Glucose, triglycerides, TMAO (a metabolite of meat breakdown)
Vegan’s diet satisfaction decreased. This means they weren’t super pleased with their diet intervention.
Based on these results, it seems like we can conclude that a vegan diet is best for optimal health, right?
Ahhhhhhhhhh, not so fast.
As Oscar Wilde famously said:
"The truth is rarely pure and never simple."
Here’s the deal:
There are many issues with this study that were swept under the rug. However, understanding these nuances is CRUCIAL for the study’s context and real-world applications.
Let’s dive into a few:
Uncovering the Gray Areas
1. Researchers focused exclusively on LDL to decide which diet outperformed the other, but more and more research is showing that LDL is not the cause of heart disease.
LDL is a risk factor for heart disease, but it needs to be looked at in the context of overall diet and lifestyle, stress, inflammation, and family history to understand a person’s risk fully.
This brings me to point number 2….
2. Twins followed a “healthy vegan diet,” but what does that mean for the real world? A vegan diet can be just as ultra-processed as the Standard American Diet. In fact… studies show that higher avoidance of animal foods is associated with higher intake of ultra-processed vegan food and a higher BMI.
In the Stanford study, plant-based “meat” intake increased sevenfold – that’s a whopping 700%! Many plant-based products are ultra-processed junk re-branded (i.e., vegan butter, cheeses, Beyond Meat, Impossible Meat), riddled with seed oils and low-quality ingredients that drive inflammation. Less saturated fat might lower LDL, but inflammation is also a major risk factor for heart disease.
3. Weight loss and fasting insulin were not included in the initial study design. They were added retrospectively after they were shown to favor vegans, which suggests cherry-picking data and questions if other data was manipulated to yield favorable outcomes.
4. Researchers did not control for the impact of weight loss on LDL. How much of the reduction in LDL was due to consuming fewer calories? This isn’t a bad thing, but it makes me wonder why they didn’t control for weight loss as a confounding variable. Perhaps because weight loss was linked to less dietary satisfaction?
5. The trial only lasted eight weeks. This is a drop in the bucket compared to a lifelong commitment to a vegan or plant-based diet. The study does not weigh the long-term risks of a vegan diet (i.e., nutrient deficiencies, anemia, muscle wasting). Plus, there was no follow-up period to assess sustainability, adherence, or long-term satisfaction.
6. Can the findings be generalized to the broader population? Christopher Gardner, lead researcher and director of the Stanford Plant-Based Diet Initiative, seems to think so. In the study’s press release, he says, “Our study used a generalizable diet accessible to anyone because 21 of the 22 vegans followed through with the diet.”
Let’s zoom out for a second…
The study was conducted in healthy twins from Stanford.
77% of the cohort was female
72% were white.
11% were Asian,
5% were Black, and
2% were Pacific Islander
Minority groups were underrepresented, as were disparities in socioeconomic status and education. Thus, is the notion that a vegan diet is beneficial for all reflective of the entire population? What about less privileged people?
Or those in rural areas without access to fresh produce?
Or those who can not afford proper supplementation?
My guess is probably not….
7. The authors do not address nutrient deficiencies (beyond B12). B12 gets all the attention as a nutrient of concern on a vegan diet, but omega-3, Vitamin A (retinol), B vitamins, vitamin K2, calcium, vitamin D, heme iron, zinc, iodine, selenium, and choline are also dangerously low or near absent on a vegan or plant-based diet. You can get these nutrients from plants, but at lower levels that are less bioavailable.
A proper vegan diet requires LIFE-LONG planning & supplementation. Even then, supplements can’t always make up for the deficits, which often don’t show up for months or years into a vegan diet.
What about conflicts of interest?
These are the vested interests of Big Food companies that can (and do) influence study results.
This is nothing new in the world of nutrition research. A 2018 report showed that Big Food funded 13% of research studies in nutrition journals, and 56% reported findings favorable to the industry’s interests. Big yikes!
Here are a few MAJOR 🚩🚩🚩 of the Stanford Twin Study:
1. Professor Christopher Gardner, the Director of the Stanford Plant-Based Diet Initiative, has been vegan for over 40 years.
Gardner openly admits that his research is influenced by his personal values regarding animal rights, environmental concerns, and climate change rather than a sole focus on nutrition and health. This raises the concern that Gardner’s dietary ideology might bias his research and favor vegan diets.
Gardner admits to receiving funding from Beyond Meat “outside the submitted work” in the study’s Conflict of Interest Disclosures (see below). How could receiving money from one of the biggest vegan food brands in the world not influence his work?
Additionally, Gardner serves on the U.S. Dietary Guidelines Advisory Committee (DGAC).
In a new report by the non-profit public health research group, U.S. Right to Know, HALF of the DGAC was spotlighted for concerns about conflicts of interest influencing national nutrition policies. Gardner was one of the committee members.
He also leads the Stanford Plant-Based Diet Initiative (PBDI), which Beyond Meat proudly funds.
This suggests Gardner’s advocacy might be masquerading as science, especially since the PBDI already posits plant-based diets as superior, raising doubts about the neutrality of its scientific research.
2. The study was funded by the Vogt Foundation, a vegan philanthropy group, but the funding/support section failed to disclose the foundation's advocacy nature.
The Vogt Foundation has financially supported vegan-promoting films like "Game Changers" with an $850,000 donation and $600,000 to the Oceanic Preservation Society (OPS), a production company dedicated to environmental advocacy. The same production company that also filmed the Vegan Twin Study.
Could the involvement of the Vogt Foundation suggest a broader agenda to influence public opinion through media, further complicating the landscape of unbiased research in this area?
Conflicts of interest and biases aside….
Is a vegan is a vegan diet really better for overall health?
The truth is, it depends.
Going from a SAD → Whole-Food, Plant-Based Diet = Beneficial
If your average overweight or obese American goes from eating a Standard American Diet (SAD) of ultra-processed food, takeout, refined carbs, oils, added sugar, and saturated fat to a whole-food plant-based diet, you will no doubt see a benefit, mainly from ingesting less ultra-processed foods, fewer calories, more fiber, antioxidants, etc. This can translate to benefits for weight loss and positive changes in LDL and total cholesterol.
Failure to Supplement for Deficiencies = Harmful
We also have to consider the implications of nutrient deficiencies and how this impacts health long-term.
Omega-3s. The plant-based omega-3, alpha-linolenic acid, is not easily converted into EPA and DHA (the active form of omega-3s found in salmon and other fatty fish), which perpetuates deficiencies down the line.
Vitamin B12. You must take methyl-cobalamin, NOT cyanocobalamin. Methylcobalamin is the active form of vitamin B12. Cyanocobalamin must be converted, and many people have issues doing so, resulting in toxicity over time.
Vitamin A (retinol = active form): beta-carotene and carotenoids are the pre-form of vitamin A that your body must convert to retinol, which it isn’t super efficient at doing.
Iron. The primary source of iron on a vegan diet is non-heme iron, which is bound to anti-nutrients and more difficult to absorb than heme iron. Flour and grains enriched with iron are recognized and used in the body in the same way as heme iron.
Calcium in spinach and collard greens is bound to oxalates, which inhibit its absorption.
Vitamin D3. Essential for bone, immune, mood, and hormone health. Only found in fatty fish (salmon, sardines, anchovies) is more bioavailable than plant-based D2.
Conjugated linoleic acid. Found in meat and dairy from ruminants like cows and sheep, CLA has been linked to fat loss and improved metabolic health.
Creatine: The body can make creatine, but additional amounts from animal products like meat can enhance muscle mass, strength, and exercise performance.
Carnosine: an antioxidant that may improve muscle function and neurological health. It's particularly abundant in beef and poultry.
Taurine: an amino acid found in meat, fish, and dairy that is important for bile salt formation, eye health, and heart function.
Getting Enough Protein = a Challenge
It is possible to get enough protein on a vegan diet. It’s just slightly more challenging and takes carefully planning out your meals and structuring them to contain all of the essential amino acids. You also have to eat more to get the same amount of protein from animal foods, often accompanied by carbs and sugar, increasing calorie intake and making muscle gains more difficult.
Prioritizing complement proteins, like grains and legumes, and supplementing with high-quality protein powder will make it easier to reach the goal of one gram of protein per pound of ideal body mass.
Younger generations can adapt and make do, but as we grow older, it becomes harder and harder to digest, absorb, and integrate protein (of any kind) into muscle tissue.
Will Going Vegan Solve the Climate Crisis?!
I really wish that saving the planet was as simple as choosing plants over meat. The Netflix Docuseries might have you think that it is…
There’s no denying that factory farming is unsustainable from an environmental, animal welfare, and human health perspective.
But the way we grow corn, wheat, and soy (staples of plant-based and feedlot cows’ diets) is not any better.
Harsh agricultural practices are used to grow corn, wheat, and soy mono-crops – the same plants used to make Beyond Burgers and Impossible Meats.
Monocropping and tilling are terrible for the soil. It strips it of essential nutrients, like magnesium, zinc, and copper, resulting in nutrient-depleted fruits and vegetables.
Harvesting wheat, corn, and soy with heavy machinery kills approximately 7.3 billion wild animals every year. It’s responsible for the loss of 50% of our bird species.
Herbicides and pesticides are major sources of greenhouse gas emissions that destroy the organic matter in the soil, rivers, lakes, and streams.
Almond milk has single-handedly decimated the bee population. 35 billion pounds of pesticides are used on almonds every year, wiping out one-third of bees in the US due to disease and toxicity.
ALL industrial farming is destructive – animals AND plants.
It’s not the COW it’s the HOW.
I haven’t seen the Netflix Documentary yet, but I’m assuming that this critical piece of information in the vegan/climate change argument was left out.
How can we go plant-based or vegan and continue to employ the destructive agriculture practices that have gotten us into this mess?
The solution?
Many experts call on regenerative agriculture.
The idea is to place cows back in their natural habitat – to graze among pastures. Grazing cows helps fertilize the soil naturally (with poop!).
This helps to rebuild and regenerate the soil, which is the best way to sequester carbon from the atmosphere in a holistic manner. It brings back pollinators, insects, and wildlife and limits the use of fertilizers, pesticides, and herbicides using no-till methods, compost, and cover crops.
I highly recommend watching the Netflix Documentary Kiss The Ground to get a full-spectrum view of what exactly regenerative agriculture is and how it can be used to fix the climate crisis.
Final Thoughts
Any nutrition study that claims they've got the answers should always be taken with a grain of salt. This study, in particular, points out how hard it is to employ a one-size-fits-all approach to diet or focus on one specific marker (like LDL) as the end-all-be-all of health and wellness.
I’m not against veganism; when executed correctly, it can certainly be beneficial for Americans, especially those moving from a SAD.
All I’m saying is nutrition is not black or white, like the movies may make it seem. There are many factors, both seen and unseen, that influence the dietary guidelines and the making of movies like this.
Diet a spectrum. There is no “magic diet” that’s going to work for everyone. It’s all about finding the right nutritional approach, which means considering independent variables like genetics, health goals, income, family history, ethnicity, and the lifestyle you wish to lead.
I hope this newsletter really helps hammer home the need to stay open-minded and ask questions when met with such strong, well-done, and influential media. I hope even more that this inspires you to find a dietary approach that aligns with your unique body, right to optimal health, and environmental impact.
