Written by: Katherine Walcott; SLU Dietetic Intern
If you’re at all interested in nutrition (or frankly, if you’re at all on the Internet), you’ve seen your fair share of nutrition articles that seem, well, too good to be true… to put it nicely. As someone studying nutrition, I am constantly being sent these types of articles, such as “Study on Strawberries and Brain Health Bears Fruit”1 or “Sweet Discovery: Eating Chocolate Can Add Years to Your Life.”2 I am also constantly being asked my opinion on new shows or documentaries, such as Netflix’s “You Are What You Eat: A Twin Experiment”3 or “Live to 100: Secrets of the Blue Zones.”4 And while I hesitate to speak for anybody, I am fairly confident that I speak for most nutrition professionals when I say the answer is almost always, well, complicated.
Which is frustrating, right?! Trust me, I get it. If I could give patients (and well-meaning family members who fill my inbox with these articles–if you’re reading this grandad I promise I read them) straightforward and simple answers, I would. But as a future dietitian, I know I’d be lying. So let’s dig in deeper, shall we?
Let’s start with Netflix’s “You Are What You Eat: A Twin Experiment.”3 Let me start by saying that, overall, I really enjoyed the show. I agreed with many of its general premises, but it also left me with a lot of thoughts, which I will do my best to succinctly sum up for you.
Cover art for Netflix’s “You Are What You Eat: A Twin Experiment” featuring 4 pairs of identical twins who enrolled in an 8-week study evaluating the effect of a vegan vs. omnivore diet on cholesterol, weight, and other nutrition-related measures.3
When I first heard about the show and watched the trailer, I thought I was going to be watching a quick 4 episodes about an interesting nutrition research study. However, I quickly realized the show was about much more. While its central theme was the study, it expanded outside of the study to talk about issues of inequity in our food system, antibiotic use in farm animals, food safety measures in the meat industry, the food industry's role in marketing, emerging plant-based products on the market, and even how diet affects the sexual response. (I don’t think I’m alone when I say I was not expecting episode 2 to start off with the twins watching pornography in a research lab.)3
After watching the series, I wanted to read the original study to see how it compared to the show. The study’s title is “Cardiometabolic effects of omnivorous vs vegan diets in identical twins a randomized clinical trial.”5 Like the show, let me start off by saying I enjoyed the read (nerdy, I know) and agreed with many of the points made in the introduction and discussion. However, I was shocked to find no mention of the word “exercise” or “physical activity” anywhere in the paper5 despite exercise playing a major role in the Netflix show.3 Since exercise is one factor that can affect cholesterol levels6 (the primary outcome of the study5), this surprised me.
Visual abstract for “Cardiometabolic effects of omnivorous vs vegan diets in identical twins a randomized clinical trial,” the study behind Netflix’s “You Are What You Eat: A Twin Experiment.”5
I was also surprised to find that, in contrast to the documentary portraying the first 4 weeks as being strictly controlled through delivered meals,3 in the study participants were allowed to supplement these meals with snacks they purchased (though they did have to follow guidance from health educators).5 Another thing that seemed different to me from the show was that those on the vegan diet consumed 13-14% of their calories from protein while those on the omnivore diet consumed 20% of their calories from protein.5 To me, the show seemed to portray these diets as being equal in all but animal foods. (The show also hammered home that those on the vegan diet lost more muscle than those on the omnivore diet... I wonder why.3)
What surprised me the most however, was the demographics of the twins, which I felt seemed very different from what was portrayed in the documentary. Of the 44 twins who participated in the study, 77.3% were female, the average age was 39.6 years, 95.5% had achieved at least a college level of education, 72.7% were white, and average BMI was 25.9 (considered to be on the borderline of healthy and overweight7–though I think we can all agree BMI is a flawed way to look at health). Additionally, the researchers excluded people with a number of characteristics from participating, including those with high cholesterol (specifically LDL-C ≥190 mg/dL for my nutrition nerds out there5,7); those with high blood pressure (systolic blood pressure ≥160 mmHg or diastolic ≥90 mmHg for my nerds3,8), those with diabetes, and those taking medications for diabetes, unhealthy lipid levels, high blood pressure, and even psychiatric disorders.5
Now, before anyone says I’m poo-poo’ing the study, I’m not. Researchers can’t control everything participants do during studies, sometimes the participants they can get just don’t end up being that diverse, and often they have to exclude people with certain characteristics. I agree with their exclusions, but I do think it draws an interesting contrast to a documentary that to me seemed aimed at Americans with (or at risk of developing) diabetes, hypertension, and other diet-related diseases.
As a scientific research article, the study itself was a great read, and as a Netflix nutrition documentary, the show was a great watch. However, every study and every show has its flaws, no matter how small they are. If we're not careful, we can forget that there is always nuance in nutrition because there are always differences among people. (Hence the irritating, seemingly never straightforward but nonetheless well-intentioned answers to your nutrition questions.)
Speaking of studies and their flaws, remember the strawberry one I mentioned at the top? Let’s look at that one, shall we? I’m sure we will find no flaws or nuance whatsoever… right?
Completely reliable, entirely unquestionable 8-word summary of a completely reliable, entirely unquestionable research study that is definitely not funded by the California Strawberry Commission.1,9
The original article I was sent (shoutout to my grandfather who gave me fodder for this post) is titled “Study on Strawberries and Brain Health Bears Fruit.” After reading the article, you’d think that eating strawberries improves memory, reduces depression, and may reduce the risk of dementia.1 However, after reading the study, you’d think something else. (To be clear, I think regularly eating fruit–as well as vegetables, whole grains, nuts, seeds, fish, etc.–is beneficial for one’s health and will reduce one’s lifetime disease risk. What I take issue with is the implied promise that eating strawberries could prevent dementia.)
Looking at the actual study itself, it enrolled 34 people with "complaints of mild cognitive decline" (very broad and subjective if I do say so myself) aged 50-65 with overweight BMIs and put them through a round of cognitive and mood tests. It then fed half of them 13 grams of strawberry powder a day for 12 weeks (what it claims is equal to 1 cup of fresh strawberries) and half of them a placebo powder before putting them through these same tests again. Interestingly, when we look at who was excluded from the study, anyone with an actual diagnosis of cognitive impairment or a psychiatric condition was excluded. (So too was anyone with diabetes, kidney disease, liver disease, or regular use of certain medications or dietary supplements.) Also interesting is that, at the end of the study (by which point most people have gotten bored and stopped reading–trust me, I get it), it says “This research was supported with funding and donation of strawberry and placebo powders by the California Strawberry Commission, Watsonville, California 95076, USA.” But under Conflicts of Interest it says “The authors report no conflict of interest.” … Are we sure about that?
Anyways, now that I’ve given you my opinions on the Netflix documentary and dissected that study, what is my point? Well, I wanted to show how nutrition research and recommendations can often feel complicated, super specific, and all-or-nothing. As for why things are this way, well, documentaries have to be interesting to make money, and strawberries have to be marketed to get sold. This doesn’t make documentaries or strawberries bad, but it does create a world where you, the consumer of information, have to ask a few questions. Questions like, who is behind this recommendation, what are they saying, what are they not saying, do they have any motivation for saying this, and so on. It can be tiring, but it gets easier (and forming your own opinions is more fun anyways.) It does make you wonder though, why are nutrition recommendations always changing, and why do they always have to be so complicated?
Well, they aren’t, and they don’t.
Sure we’re still learning a lot about specific compounds in foods and specific diets, but overall nutrition recommendations have stayed pretty constant for decades.10 In the 1940s, Americans were encouraged to eat 7 categories of food, 3 of which were fruits and vegetables. In the 1950s to 1970s, this was simplified to 4-5 groups, one of which was fruits and vegetables. This stayed consistent through the 1980s, though the graphics improved (though they still leave much to be desired by today’s standards). In the 1990s, recommendations were made into a food pyramid, with 5-9 servings of fruits and vegetables being recommended daily, and in the 2000s the pyramid got a new look. (This one is personally my least favorite… if you were curious. I think it's too confusing, and not in the fun now-I-get-to-ask-more-questions way, but in the what-do-those-weird-colored-vertical-lines-mean way.) Finally in the 2010s we got MyPlate, the graphic used to educate people on what to eat today. While this graphic doesn't give specific servings11,12 (as servings differ for everyone13), it leaves no doubt that half of one's plate should be fruits and vegetables (and even more than half should come from plants).11,12
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So why did I just give you that super fun, super interesting (don’t lie, you know you loved it) history lesson? Well, just to show that, despite the documentaries guilt-tripping us into believing there is no place for animal products in our diet or the industry-funded studies brainwashing us into believing their food is the best food for our brains, overall nutrition guidance has not changed much over the years. So if you’re lost amid the sea of seemingly never-ending, always-changing nutrition “research,” relax. The one thing the Netflix documentary, strawberry study, and 100 years of USDA guidelines have in common? They tell you to eat plants.
… And if you’re still not satisfied with that answer, that’s what dietitians are for. Come talk to us. We’d love to have you. :)
