You Are What You Eat: What Does the 2023 Stanford Twins Nutrition Study Really Show?

“Proof that disputes the established order will at all times be controversial, whether or not it’s true or not, as a result of that’s the very definition of controversy: disagreement over standard understanding… To downplay scientific proof as a result of it’s controversial is to downplay scientific proof for the exact same, basic cause that science is well known.” T. Colin Campbell, Introduction to The Way forward for Vitamin

On the finish of November 2023, Stanford diet researchers together with Christopher Gardner, PhD, printed the findings of a new twin study within the Journal of the American Medical Affiliation (JAMA).^[1] Six weeks later, a four-part documentary sequence concerning the research, You Are What You Eat: A Twin Experiment, debuted on Netflix.^[2] Given the eye garnered by the research and miniseries, I made a decision to dig into the analysis, digesting not solely the JAMA paper but additionally the paper’s prolonged dietary supplements, which supply a lot better element on the research design and embody all the information printed so far.

The eight-week medical research is, in lots of respects, an ideal pure experiment. Researchers randomly assigned half of every equivalent twin pair to a “wholesome vegan weight-reduction plan” and the opposite half to a “wholesome omnivorous weight-reduction plan,” thus robotically eliminating the confounding influences of age, intercourse, and genetic elements on medical outcomes and permitting the differential affect of the 2 diets to be measured. Variations in medical outcomes have been discovered as early as 4 weeks into the research. By the tip of the eight-week research, researchers discovered that the twins consuming a “wholesome vegan weight-reduction plan confirmed considerably improved low-density lipoprotein ldl cholesterol (LDL-C) focus, fasting insulin degree, and weight reduction in contrast with twins consuming a wholesome omnivorous weight-reduction plan.”

The authors conclude their paper by summarizing their observations and providing a considerably timid suggestion for clinicians: “On this randomized medical trial, we noticed cardiometabolic benefits for the wholesome vegan vs. the wholesome omnivorous weight-reduction plan amongst wholesome, grownup equivalent twins. Clinicians might contemplate recommending plant-based diets to cut back cardiometabolic threat elements, in addition to aligning with environmental advantages.” Those that haven’t learn the research may very well be forgiven for concluding that the principle message is that folks simply must eat extra crops, versus additionally eliminating animal merchandise. In an interview to publicize the research’s findings for Stanford Drugs Information, Gardner acknowledged, “What’s extra vital than going strictly vegan is together with extra plant-based meals into your weight-reduction plan.”^[3]

I can solely speculate as to why Gardner framed the research’s conclusion on this watered-down vogue. Maybe he needed to enchantment to the big majority of the general public that might reflexively dismiss the thought of switching to a 100% plant-based weight-reduction plan. Maybe he was additionally cognizant that his rising visibility, on account of the Netflix documentary, may make him a goal for the ire of authorities within the meals business, particularly if he have been to attract consideration to the damaging affect of overconsumption of animal protein on cardiometabolic well being, not to mention advocate the elimination of meat and dairy merchandise from the nation’s weight-reduction plan.

Beneath, I argue that primarily based on the research’s knowledge such wishy-washy framing of the outcomes is deceptive. Whereas the outcomes do certainly assist the adoption of a plant-based weight-reduction plan, the restricted recommendation to incorporate extra plant-based meals in your weight-reduction plan does a disservice to the general public by neglecting to publicize the obvious contributor to the helpful affect noticed for the vegan group in comparison with the omnivorous group: the absence of animal merchandise.

Research Background

The start line for this twin research is the popularity that “Considerable proof from observational and intervention research^{[4][5][6][7][8][9][10]} signifies that vegan diets are related to improved cardiovascular well being and decreased heart problems, probably due to the upper consumption of greens and fruits, legumes, entire grains, and nuts and seeds in contrast with different several types of dietary patterns.^[11]” We are able to see from this framing that already the researchers keep in mind that the rise in plant-based meals is the first think about selling cardiovascular well being. There is no such thing as a point out by any means of animal protein. The authors then level out that many of the research wanting into the well being advantages of vegan diets have been epidemiological slightly than medical, they usually categorical concern about confounding variables in epidemiological research. Particularly, they notice the “bias of self-decided vegans who might differ from nonvegans in elements which will affect weight-reduction plan and well being.” It is a affordable concern for epidemiological research carried out within the US and different extremely industrialized nations. Nevertheless, it means that the researchers are both unaware of the China Research or don’t imagine its findings are related. Because the China Study was carried out in rural China at a time when diets in any given village have been remarkably homogeneous, at the same time as they differed from these in different villages, the confounding impact described was irrelevant. Peasants in any given village didn’t “self-decide” between meat-heavy and vegan diets. That they had no alternative within the matter. Dr. Campbell was in a position to examine well being outcomes throughout greater than 100 villages that differed of their typical weight-reduction plan, particularly within the steady variable of the proportion of energy coming from animal protein.

Research Design

The Stanford research was revolutionary in that it in contrast 22 pairs of equivalent grownup twins assessed to be wholesome on the outset of the research (primarily based on extensively accepted markers of cardiovascular well being equivalent to BMI, LDL ldl cholesterol, and blood stress) and randomized to comply with both a “wholesome vegan weight-reduction plan” or a “wholesome omnivorous weight-reduction plan,” each of which have been designed to be “replete with greens, legumes, fruits and entire grains and void of sugars and refined starches.” The researchers advised the individuals in each teams to eat till they have been satiated. No effort was made to make the 2 diets isocaloric (i.e., of equal complete vitality), so calorie consumption was not managed for.

Physique measurements and lab checks have been accomplished at baseline, 4 weeks, and eight weeks. Stool samples have been additionally collected at common intervals for future evaluation. For the primary 4 weeks, all meals have been supplied by a meal service referred to as Trifecta Nutrition. Throughout this preliminary interval, the research topics additionally obtained well being educator counseling on how to buy and put together meals that adhered to the factors for the beneficial nutritious diet. Within the second 4 weeks, they shopped for and made their very own meals and had entry to well being educator assist. Members have been requested to log their meals consumption utilizing the Cronometer app. The meals log knowledge was shared in actual time with well being educators, permitting them to proactively attain out to individuals to assist them course right and persist with the rules.

The graphic under, proven because it seems in complement 2, illustrates the research design.

Research Outcomes

At eight weeks, the vegan group had considerably improved LDL-C, fasting insulin degree, and weight reduction relative to the omnivorous group. The variations are particularly spectacular given the quick size of the research and the truth that the baseline values of those measures have been thought-about regular. The desk under exhibits the week eight knowledge in comparison with baseline values. The metrics highlighted by the research authors are shaded inexperienced.

Why Did the Vegan Group Do Higher?

Regardless of the numerous variations in key measures of cardiovascular and metabolic well being between the participant teams on the eight-week mark, the JAMA paper doesn’t take a powerful place on this query. The researchers state, “Though our findings counsel that vegan diets supply a protecting cardiometabolic benefit in contrast with a wholesome, omnivorous weight-reduction plan, excluding all meats and/or dairy merchandise is probably not crucial as a result of analysis^[12][13] means that cardiovascular advantages may be achieved with modest reductions in animal meals and will increase in wholesome plant-based meals in contrast with typical diets.”

To reply the query, I delved deep into complement 2 (linked to the principle paper) and targeted on two issues:

1. What precisely have been individuals advised to eat to be compliant with their particular weight-reduction plan?
2. How carefully did individuals adhere to that steerage? (i.e., what did they really eat?)

Dietary Steering

Well being educators gave detailed directions to every group, together with particular targets for the variety of day by day servings of various sorts of meals:

• The wholesome omnivorous weight-reduction plan group was advised to eat sufficient animal merchandise day by day to distinguish from the vegan group. Particularly, this included targets of six to eight ounces of meat, fish, or poultry, one egg, and one and a half servings of dairy every day, on common. Except for animal merchandise, targets included three servings of greens, two servings of fruit, and 6 servings of grains or starchy greens every day.
• The wholesome vegan weight-reduction plan group was advised to keep away from all animal merchandise for the course of the research. Particular targets included six or extra servings of greens, three servings of fruit, 5 servings of legumes, nuts, seeds, or vegan meat, and 6 servings of grains or starchy greens every day.

For ease of comparability, these pointers are summarized within the desk under. No restrictions have been imposed on using salt or fatty plant meals, together with oils. No dietary supplements have been supplied.

Moreover, to make sure that each teams of individuals would devour diets “more healthy in comparison with their pre-study dietary sample demonstrated by elevated vegetable consumption and decreased refined grains consumption [emphasis added],” well being educators instructed all research individuals to:

1. Select minimally processed meals.
2. Construct a balanced plate with greens, starch, protein, and wholesome fat.
3. Select selection inside every meals group.
4. Individualize these pointers to satisfy preferences and desires.

How carefully did individuals adhere to the steerage for his or her particular weight-reduction plan?

Complement 2 offers summaries of self-reported meals consumption at baseline, following the meals supply part (week 4), and following the self-provided part (week eight). These knowledge have been gathered through unannounced 24-hour dietary recall interviews with individuals which have been carried out thrice throughout week zero (baseline), thrice throughout week 4, and thrice throughout week eight.

The chart under exhibits the change within the common variety of servings per day of various meals teams in comparison with the baseline consumption.

It’s instantly obvious that for each vegan and omnivorous teams the rise within the variety of servings of non-starchy greens (inexperienced bar) is modest relative to modifications within the principal supply of protein; i.e., animal versus plant protein. The omnivorous group ate extra meat every day than at baseline whereas the vegans ate none. In the meantime, the rise in veggie servings for vegans shouldn’t be a lot better than the rise for omnivores. Starchy vegetable consumption really fell for the vegan group and barely moved for the omnivorous group. The chart additionally illustrates that whereas each teams of individuals decreased their consumption of refined grains, they barely elevated their consumption of entire grains.

In abstract, adherence to the particular dietary targets was strongest for the consumption or exclusion of animal merchandise. It’s more durable to evaluate how properly individuals adopted the final dietary steerage, equivalent to guaranteeing selection and steadiness throughout meals teams. What we do know is that the vegan group primarily substituted animal merchandise with meat options (vegan meat). Since most of those are extremely processed, it appears probably that their weight-reduction plan was comparatively heavy in ultra-processed meals, regardless of the route to decide on minimally processed meals.

A Missed Alternative

A mere look on the knowledge in complement 2 reveals that each the suggestions and the precise weight-reduction plan consumed by the vegan group through the eight weeks fall manner quick of a complete meals, plant-based (WFPB) weight-reduction plan. The vegan weight-reduction plan’s optimistic affect on cardiovascular and metabolic well being, whereas statistically important, was probably much less spectacular than what may have been achieved inside the eight-week timeframe with a vegan weight-reduction plan that extra carefully resembled a WFPB weight-reduction plan.

As Dr. Campbell writes in The Way forward for Vitamin, the WFPB diet may be described in a dozen phrases, distilled to 2 suggestions:^[14]

1. Eat a wide range of entire, plant-based meals.
2. Keep away from consumption of animal-based meals.

Regardless of claims on the contrary, the researchers created a vegan weight-reduction plan that, when carried out, was largely outlined by what it eradicated slightly than what it emphasised. Whereas the vegan individuals did certainly keep away from virtually all animal protein—all meat, dairy, and eggs—they weren’t suggested to devour solely entire crops. Their diets have been meant to be “minimally processed,” however they weren’t advised to exclude oils or meat options which are typically extremely processed and laden with oil. The truth that vegan individuals relied closely on vegan meat through the meals supply part and the self-provided part means that this was a design alternative, not a bug. On the plus facet, individuals have been advised to “select selection inside every meals group.” Had they met the targets for greens and chosen entire grains as a substitute of refined grains, their diets would have aligned extra carefully to optimum.

The macronutrient distribution chart under, pulled from complement 2, exhibits that fats consumption for the vegan group by no means dipped under 36 p.c of complete energy, as in comparison with CNS’s suggestion of 10 p.c, the typical proportion of energy that fats contains in entire crops. Protein consumption fell to 13–14 p.c, which is barely increased than CNS’s suggestion, whereas carbohydrate consumption elevated solely barely from 45 to 48 p.c through the meals supply part and as much as 51 p.c through the self-provided part. Carbohydrate consumption thus fell properly under the 70–80 p.c that CNS recommends.

Since we all know that the researchers labored with Trifecta to “develop menu choices to match a wholesome vegan and omnivorous weight-reduction plan, which emphasised greens, fruits, and entire grains whereas limiting added sugars and refined grains,” it appears affordable to imagine that the weight-reduction plan the vegan individuals consumed through the first 4 weeks carefully matched the intent of the researchers. That mentioned, to “meet their vitality necessities,” individuals have been allowed to buy and devour snacks along with their three supplied meals, so we can not know for positive.

The Backside Line: Unfulfilled Potential

The Stanford Twin Vitamin Research (TwiNS) is garnering a substantial amount of consideration and serving to to shift the Overton Window on what counts as acceptable information in diet. Nonetheless, I can not assist however be dissatisfied that the researchers held again from articulating the clear findings associated to animal protein. Buried in complement 2, there may be an acknowledgment that “Vegan individuals’ consumption of protein overwhelmingly got here from plant-based sources, whereas nearly all of omnivorous individuals’ consumption of protein got here from animal-based sources [emphasis added].” However there isn’t any dialogue of the significance of this stark distinction within the diets and no acknowledgment of the comparatively modest distinction in vegetable consumption.

The unfulfilled potential of the research is quite common in dietary research and seems to mirror low expectations round individuals’ capability to make radical modifications to their diets. (To be taught extra concerning the difficulties of making an attempt to attain optimum well being with solely reasonable modifications, examine the dietary pleasure trap.)

As Dr. Campbell writes in The Way forward for Vitamin, there are a lot of examples of how “the scientific group selectively prohibits sure ‘controversial’ topics (once they threaten the established order) from dialogue.” Till main researchers like Gardner (who has been principally vegan for many years) are keen to be extra direct concerning the consequential affect of animal merchandise, particularly animal protein, on cardiovascular and metabolic well being, we aren’t going to meaningfully shift the discourse.

Having mentioned that, I do look ahead to extra papers primarily based on this research. The paper notes, “Stool samples have been collected for future evaluation to look at modifications to the intestine microbiome, metabolites, inflammatory markers, and extra well being elements.” Such research could be fascinating provided that even equivalent twins usually have significant variations of their microbiome. Hopefully, extra evaluation will likely be launched over time, together with on the degrees of dietary adherence and the relative affect of animal product consumption versus plant consumption on microbiome well being.

References

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2. Psihoyos L, dir. You Are What You Eat: A Twin Experiment. Launched January 1, 2024, on Netflix.
3. Moskal E. Twin analysis signifies {that a} vegan weight-reduction plan improves cardiovascular well being. Stanford Drugs Information. November 20, 2023. https://med.stanford.edu/information/all-news/2023/11/twin-diet-vegan-cardiovascular.html
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