Do Autoimmune Diets Really Work?

Placebos and the problem with anecdotal evidence about diets

This post is from my previous newsletter, Food Psych Weekly.

Welcome back to Food Psych Weekly, the newsletter where I answer your questions about intuitive eating and the anti-diet approach.

I’m so grateful to everyone who sent kind words in response to last week’s newsletter announcing my new book, The Wellness Trap. Thanks to everyone who pre-ordered it, it was a #1 bestseller in its category on Amazon last week! I’m floored by the response and can’t wait for you to read it when it comes out in April.

This week’s question is related to some of what I cover in the book—specifically the lack of good evidence for many diets and other practices that are promoted in wellness culture, and the intense pressure that it puts on those of us with chronic illnesses to restrict our eating.

And just a quick content warning: there is a specific “wellness” diet mentioned in the question and my answer.

The question is from a reader named Cassie, who writes:

I have been following your podcast for years and originally found you because of a podcast episode you did regarding autoimmune disease and seeking actual medicine instead of changing diet, since there’s so little good evidence for dietary changes. A while ago I did a blood test for food sensitivities and it basically told me that all veggies were inflammatory.

On the one hand I really, really want to believe that autoimmune disorders can’t be “cured” by diet. At the same time, my rheumatologist has recommended several dietary changes that are pretty extreme, without any scientific evidence to back that up other than patient testimonials, and those in a support group I follow also say that they’ve found relief from an autoimmune protocol diet.

I have a history of binge eating disorder and still have a lot of shame that in all likelihood I wouldn’t even be able to follow a really restrictive diet because I’d almost immediately have behaviors (even thinking about it makes me nervous!). It’s so hard to navigate this feeling that I’m bringing this all on myself. It’s just really sad and frustrating, especially when I don’t feel good. Any advice?

Thanks, Cassie, for that great question. Before I answer, just my standard disclaimer:

These answers are for informational and educational purposes only, aren’t a substitute for individual medical or mental health advice, and don’t constitute a provider-patient relationship.

I’ll be giving fairly quick and unpolished answers here for the foreseeable future because I’m trying to juggle work and caring for a new baby, but hopefully this will be a helpful start.

I’ve been thinking a lot lately about how integrative and functional medicine and other forms of wellness culture often claim to “treat the whole person,” and yet they actually ignore a lot of our personhood.

For humans, food is not merely a set of interchangeable inputs that can be swapped around at will without disrupting us in some way. It’s not like cogs in a machine. We all have relationships with food and likely will have some feelings about being told we can’t eat certain things and must eat others. (Even those rare people who don’t care much about food and wish they could just “take a pill” to get their food needs met are still inconvenienced by having to overhaul their diets.)

Food is culture, comfort, connection. Food is fun and pleasure. Diets deny us those things, and in the process they disconnect us from the fullness of our humanity, our selves.

I’d wager most people struggle to make the kinds of sweeping changes to their menus that wellness culture recommends, because these diets are basically asking us to be robots instead of human beings. So the first thing I want you to know is that you’re not alone in having a hard time with even the idea of a restrictive diet, and there’s absolutely no reason to be ashamed.

The second thing I want to share is a little more delicate to explain, because I don’t want to inadvertently shame anyone who feels they’ve found relief from autoimmune symptoms on certain diets. I have multiple autoimmune diseases myself, and I know how draining and painful the symptoms can be (though I’m lucky that these days my flareups aren’t as bad as many people’s are, or as mine used to be). I understand how profound it can be to find something that seems to help, and I wouldn’t want to take that away from anyone.

Still, in my years of delving into the scientific literature on diets for autoimmune disorders and other chronic illnesses, I’ve found that with very few exceptions (such as the gluten-free diet for celiac disease, which is evidence-based and medically necessary), there just isn’t good science to support changing your diet to manage autoimmune conditions. Take Hashimoto’s thyroiditis, which I have: despite the increasingly common advice to go gluten-free for this condition, the best available evidence shows that the diet doesn’t have any significant impact on thyroid function for people without celiac disease.

In this research I’ve come to understand something that I think is worth considering even if you feel that a diet has been helpful—and especially if you don’t, or you’re not sure:

When we seem to feel better on a restrictive diet, often it isn’t actually because of the diet itself, but rather because of a set of other factors that might make it appear that the diet was effective.

These factors include the placebo effect (in which believing that an inert treatment will make you feel better actually does) and its lesser-known cousin, the nocebo effect (in which believing that something is bad for you, like a food, makes you feel better when you avoid that food and worse when you eat it). These effects demonstrate the power of expectations and the mind-body connection to create real, physical symptoms.

Another reason some people might perceive integrative and alternative treatments to work is that many chronic diseases go through normal fluctuations or cycles, where symptoms will get worse, then better, then worse again. If it just so happens that a person’s symptoms ebbed naturally right after a certain treatment, it can seem like the treatment was responsible when in fact it had nothing to do with it.

This phenomenon (sometimes known as the “natural history of disease” or the more technical-sounding “regression toward the mean”) is a powerful confounding factor in anecdotal evidence on wellness treatments. It’s even an issue in scientific studies: People tend to enroll in studies when their symptoms are quite bad, so it’s likely that no matter what treatment they’re given, their symptoms will improve.

Placebo and nocebo effects are also important confounders in scientific research on diets and many other integrative- and functional-medicine interventions, because for these interventions, it’s really hard to design a placebo that can fool study participants in randomized controlled trials.

Usually it’s pretty easy for people to tell what kind of diet they’re assigned to in the study; typically the researchers will explicitly tell people to avoid, say, gluten and dairy (or whatever is to be avoided on the diet being tested). And when people know what diet they’re getting, they’re going to experience placebo and nocebo effects due to their preexisting beliefs about that diet.

Thus, the people in a study who are assigned to (for example) an autoimmune protocol diet will most likely experience a placebo effect—they’ll feel better simply because they expect to on that diet. And if there’s a control group in which people are assigned to (for example) their usual diet, those folks will generally experience a nocebo effect, meaning they’ll likely feel worse. (If you really want to geek out about this stuff, check out Snake Oil Science by R. Barker Bausell, a former director of a prestigious research center devoted to studying complementary and alternative medicine who became a vocal critic of such research.)

As it happens, to date there are precisely zero randomized controlled trials of the autoimmune protocol diet, according to a PubMed search as of October 19. Instead there are three tiny, uncontrolled clinical trials (Content Warning: food- and weight-stigmatizing language, BMI numbers) with very short-term implementations of the diet, which is not good evidence to support the use of any diet (though it may be grounds for further scientific research). The small numbers of people in these studies all received the diet, and many reported symptom improvement—which is exactly what we’d expect from the placebo effect.

I’m all for honoring people’s personal experiences of healing, and of course science has its limitations. But one thing I think science excels at (when it’s well conducted and repeated over multiple studies) is determining why a particular intervention works—whether it’s because of confounding factors like expectations and the power of the mind-body connection, or whether it’s because of the intervention itself. And from what I’ve seen to date about the autoimmune protocol diet, there’s simply no evidence to support the claim that the diet itself has any benefits.

Again, this is not to take away from anyone’s healing or to shame anyone for finding relief on these sorts of diets. I’m definitely not saying that the relief is “all in your head;” quite the opposite. But what I am inviting you to consider (especially for Cassie, who asked the question) is that the anecdotal reports of symptom improvement you might hear about with diets like this often have nothing to do with the diets themselves. And if you’re someone who has a history of disordered eating and finds it challenging to go on (or even think about going on) a restrictive diet, there’s no good reason to do it. Your recovery—and your overall well-being—will likely be a lot better served by skipping the diet.

I go into all of this in more depth in The Wellness Trap, so if you’re interested in this discussion I’d love for you to check it out.

I hope that’s helpful in thinking through your situation, Cassie, and thanks again for the great question.

Ask your own question for a chance to have it answered in an upcoming edition of the newsletter.

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Here’s to skipping the diet,

Christy

P.S. If you’re interested in learning more about the problems with wellness culture, check out my new book, The Wellness Trap. It comes out in April and is available for pre-order now.