A few weeks ago, I met two of my good friends for brunch at a local Boulder restaurant where most of the menu was marked with gluten-free options.

When the waitress came over, I told her that I needed my meal to be gluten free.

She was very abrupt: “Just so you know, anything marked gluten-free will be cross-contaminated. We only have one griddle and everything is cooked on it.”

My nervous system shifted and I felt a bit uncomfortable. I found myself wondering:

What if I react?

Is this worth the risk?

I hadn’t eaten a bite of food, or even ordered yet, but my expectations had already changed. I was responding to the idea (translation: fear) of the food I was soon to eat.

But then I caught myself.

The waitress’s tone was alarmist, but I recognized that nearly every restaurant I eat at (both here in Boulder and when I travel) has gluten somewhere in the kitchen. That’s simply the reality of eating out.

Taking a breath, I consciously chose not to let her warning about possible cross-contamination become anything more than that.

My brain and body relaxed.

But as a nutrition counselor who has spent decades working with clients and many years studying the gut-brain connection, I recognized exactly what was happening.

I found myself asking the same question that often guides my work with clients: How much can our expectations influence our symptoms?

The Gluten Study

Researchers recently explored this question in people with self-reported gluten sensitivity.

Participants were given bread that either contained gluten or was gluten-free. Some were told they were eating gluten when they were not. Others were told they were eating gluten-free bread when it actually contained gluten.

The results were fascinating.

Participants who believed they were consuming gluten often reported more symptoms—even when the bread was gluten-free! In some cases, expectations appeared to have a greater impact on symptoms than the gluten itself.

Of course, this study does not prove that gluten sensitivity isn’t real. Many people experience genuine symptoms when they consume gluten. Some have celiac disease. Others have non-celiac gluten sensitivity. And many simply feel better without gluten.

But this study highlights something important: Our expectations can influence how we experience symptoms.

A College Psychology Lesson

Long before I became a nutrition counselor, I was interested in the relationship between the mind and the body.

I still remember sitting in a college psychology class learning about dissociative identity disorder (formerly called multiple personality disorder).

My professor shared that some individuals appeared to have different physiologic responses depending on which personality state was present, including differences in food allergies!

What? How was that possible?

The same person (the same body) could be allergic to a food in one personality but not in another?

That was fascinating – and hard for me to wrap my head around!

Was it possible that our thoughts, beliefs, perceptions, and internal experiences could influence our biology in ways we didn’t fully understand?

Years later, researchers would demonstrate similar concepts in much more controlled experiments.

When Beliefs Influence Biology

One of my favorite studies on this topic involves a milkshake.

Participants were given the exact same 380-calorie milkshake on two separate occasions.

One time, researchers described it as a rich, indulgent shake containing 620 calories. The other time, they described it as a sensible, low-calorie shake containing just 140 calories.

The twist?

The milkshake was identical both times. Each one, 380 calories.

Despite consuming the exact same drink, participants’ hunger hormone (ghrelin) responded differently depending on what they believed they were drinking.

When participants thought they were consuming the indulgent 620-calorie shake, ghrelin levels dropped significantly more, signaling greater satiety and satisfaction.

Think about that for a moment.

The same beverage.

The same ingredients.

The same calories.

Yet different physiological responses based on expectation.

Another small study found something similar in people with type 2 diabetes.

Participants consumed identical beverages that were labeled as containing different amounts of sugar. Remarkably, blood sugar responses more closely reflected what participants believed they had consumed, rather than what they actually consumed.

Because each participant received both versions of the beverage (high sugar and low sugar), researchers were able to compare how the same person’s body responded under different expectations.

The takeaway?

Expectations don’t just influence how we feel. They can influence measurable physiology.

When Fear Enters the Equation

When you’ve experienced unpleasant symptoms after eating, it is completely natural to become more cautious around food.

But this is where a normal protective response can start working against us.

You start reading labels.

You research ingredients.

And perhaps most importantly, you start paying very close attention to your body.

Unfortunately, that last piece can sometimes become part of the problem.

The more we fear a reaction, the more closely we watch for one.

Every shift.

Every sensation.

Every feeling becomes data.

This process is known as hypervigilance, and it is especially common in people with IBS and other chronic digestive disorders.

Hypervigilance can amplify normal sensations, increase symptom awareness, and make it much harder to determine whether a food is truly causing a reaction.

Over time, this can create a vicious cycle:

A symptom leads to fear.

Fear leads to hypervigilance.

Hypervigilance magnifies symptoms.

The symptoms reinforce the fear.

And the cycle continues.

A Complicated Picture

When someone has been struggling with digestive symptoms for years, they often come to me with long lists of foods they believe they cannot tolerate.

Sometimes those foods are genuinely problematic.

But sometimes the picture is more complicated.

After years of reacting, restricting, researching, and worrying, many people begin to expect symptoms before they even take the first bite.

I’ve seen people become afraid of gluten, dairy, FODMAPs, histamine-containing foods, lectins, oxalates, nightshades, seed oils, and dozens of other foods.

And while some of those concerns may be valid, fear can muddy the waters.

The challenge is that fear makes it harder to distinguish between a true reaction and an anticipated one.

When we expect a reaction, we become more likely to notice every sensation, interpret it as meaningful, and conclude that the food is the problem.

This is one reason why nervous system support is such an important part of healing.

The goal isn’t to convince yourself that symptoms aren’t real.

The goal is to create enough safety that you can accurately evaluate what your body is telling you.

The brain and the gut are in constant communication. Every meal is influenced not only by what we eat, but also by our past experiences, beliefs, emotions, and expectations.

Sometimes the question isn’t simply:

“What did I eat?”

It’s also:

“What was I expecting to happen?” (understanding that many expectations operate below conscious awareness)

So, What Happened After Brunch?

In case you were wondering, I felt 100% fine after brunch with my friends.

Maybe the meal contained some gluten. Maybe it didn’t.

What I do know is that before I took the first bite, my nervous system had already begun writing the story of what might happen next.

And that’s the part of digestion that often gets overlooked.

Learning to approach food with curiosity instead of fear may not eliminate every symptom. But it can help us better understand our bodies, reduce unnecessary restrictions, and begin rebuilding trust in the foods we eat—and within ourselves.

If you’re stuck in a cycle of food fear, please know that it’s possible to change by rebuilding trust and slowly teaching your brain a new story. Over time, you can learn to feel safe with food again. If you’d like support, learn more about our services and schedule an appointment with Debbie.

References

• van Tilburg MAL, Palsson OS, et al. The Role of Expectancy in Non-Celiac Gluten Sensitivity. 2024. https://pubmed.ncbi.nlm.nih.gov/38040019/

• Crum AJ, Corbin WR, Brownell KD, Salovey P. Mind Over Milkshakes: Mindsets, Not Just Nutrients, Determine Ghrelin Response. Health Psychology. 2011.https://pubmed.ncbi.nlm.nih.gov/21574706/

• Brown RJ, Pepper GV, et al. Glucose metabolism responds to perceived sugar intake more than actual sugar intake. 2020. https://www.researchgate.net/publication/344393789_Glucose_metabolism_responds_to_perceived_sugar_intake_more_than_actual_sugar_intake

• Braun BG. Psychophysiologic phenomena in multiple personality disorder. Psychiatric Clinics of North America. 1984.
• Putnam FW. Dissociation in Children and Adolescents: A Developmental Perspective.