It's complicated. (James S. Wood/AP)

Gluten, which gives bread, pizza dough and other starchy foods their chewiness, is one of the most beloved proteins in the world. But it's also quickly becoming one of the most feared — at least here in the United States. An estimated 20 million Americans believe that eating it causes them distress. And 100 million people, meanwhile, say that they are actively working to eliminate gluten from their diet.

Roughly 1 percent of humans suffer from celiac disease, an autoimmune disease that damages the body's small intestine when gluten is digested. But the gluten-free movement has gone far beyond those who suffer from celiac, becoming a pervasive part of how Americans eat.

And yet there is a growing sense that people — in particular those who don't suffer from celiac disease — are being a bit ridiculous about avoiding the protein.

Is there a scientific basis for all the gluten fear-mongering? Is it wrong to avoid gluten if avoiding it makes you feel better? And are people actually feeling better, or is it all just in their heads?

Alan Levinovitz, who teaches philosophy and religion at James Madison University, did more than merely ask these questions; he spent years pursuing answers to them. The result is a newly published book, "The Gluten Lie," which explores the origins, appeal and dangers of this latest food fad.

I spoke with Levinovitz to pick his brain about why, after all this research, the gluten-free movement is so troubling to him. The interview has been edited for length and clarity.

This whole gluten-free movement — it wasn't always a thing. How far back do you have to go to find a time when no one was talking about it?

If you went back to the 1980s, nobody would have heard of gluten. Not even health advocates. In fact, and sadly, even people with celiac disease might not have heard of gluten at the time.

I know I'm going out on a limb here, but it's safe to say that gluten-free is a big thing now. Is that right?

There's an absolutely enormous shift, from the time when people who really needed to know about the dangers that gluten posed to them didn't, to a time when far too many fear the dangers of gluten, even when the vast majority of people should feel perfectly fine about eating it.

In the late 1980s and early 1990s, so many people were being misdiagnosed with different ailments that people began to take matters into their own hands and try lots of different dietary cures. A series of books were published that claimed, in the now venerable tradition of people who vilify gluten, that avoiding the protein would not only cure celiac disease — not simply treat it, but cure it — but also a host of other ailments that modern medicine couldn't deal with, including autism.

Science, of course, has since proven none of this to be true. Autism in particular had a large influence on the spread of the gluten free movement. People with undiagnosed celiac can often present many of the same symptoms that are associated with autism, so it wasn't uncommon for people who were celiacs to be diagnosed with autism instead. What happens when these people eliminate gluten from their diets and suddenly shed the symptoms is that it looks like they cured their autism, when in fact what's happened is they have successfully treated their celiac disease.

But avoiding gluten has appealed to more than just people who have a chronic illness. How did it become so mainstream?

Around the same time that people were beginning to view going gluten-free as a potential cure for these illnesses, the paleolithic diet was gaining popularity. Early paleolithic advocates, like Loren Cordain and Tim Noakes, started to come up with their theories of ancestral health and well-being, creating these images of a paradise past when gluten didn't exist. And then of course there was Dr. Atkins, who very successfully scared an entire nation — a nation that desperately wanted to lose weight — away from carbohydrates.

So you have this perfect storm of three factors: a mythic narrative of a paradise past, when paleolithic people were healthy; a diet that could cure not only autism, but also a host of other neurological conditions; and a population that believed that the key to slimming down was avoiding carbohydrates. And gluten fit the criteria so perfectly. It was the perfect nutritional element to demonize. That's why the movement exploded.

A lot of people believe firmly in the gluten-free movement, but a lot of people are also pretty skeptical, and many of them happen to be reputable scientists. You mention in the book that the trend, for the most part, runs contrary to science. Can you elaborate on that?

One of the most important things about science is not to overstate what we know, and when you talk to people who actually research the effects of gluten, they will tell you that at this point in time there is very little that we can be certain about. At the moment, here are the things that experts on gluten can tell you we know for sure:

The first thing is that gluten causes celiac patients to become extremely ill. The only way to treat celiac disease is with a gluten-free diet, and that's 1 percent of the population. The second thing we know is that there may be a small subset of the population that has something called non-celiac gluten sensitivity. There are a few studies that show that that may be the case, and there are other studies that show that that might not be the case.

The last thing — and this is what most people forget about, or simply don't know — is that every expert agrees that most people who think that they have gluten sensitivity probably don't. When there are so many celebrities talking about how great they feel when they're not eating gluten, and so many fear-mongering doctors writing popular books about how gluten causes every ailment from Alzheimer's to ALS, you get a society in which people feel a pronounced placebo effect from abstaining from gluten and also a nocebo effect, which is the opposite, where people feel symptoms when they eat gluten, when those symptoms are actually simply psychological, not physiological.

What would you say to someone who stopped eating gluten, and then felt better? Is that a legitimate approach, on an individual level?

Of course, but I would encourage everyone to be humble about their own ability to self-diagnose. I would remind them that for decades people swore that when they eliminated MSG from their diets they stopped getting headaches, swore that whenever they had MSG, they swelled up and turned red and got rashes, even though Science shows that MSG causes no reaction. So I would caution people, I would ask them to think carefully about your mind's ability to trick you. Our tendency, as humans, is to engage in confirmation bias.

The second thing I would say is that it's extremely important if you suspect that you're sensitive to gluten to go and get tested, because celiac disease is a very serious thing, and it runs in families. You owe it to family members who may not be symptomatic to know if you have celiac, because if you have celiac then they need to get tested as well.

And then, if you don't have celiac disease, I would urge you to consider the consequences for you if you decide to eliminate gluten from your diet.

In your book you talk not only about the consequences on an individual level, but also those on a societal level. What are people not realizing?

The gluten-free movement really threatens food culture and our relationship with food. People are starting to think about diet as the main way to optimize their health, and as a consequence, their ability to sit down and enjoy a meal is diminishing. I often ask people who are seeking out the perfect diet, if in their ideal world we would all just eat the foods that allowed us to maximize the length of our life and make us as lean as possible. In that world, there is little culinary diversity. In that world, you wouldn't have different cuisines. The gluten free-movement, and a lot of what it stands for, is incredibly threatening to the beautiful diversity of culinary cultures that make life so wonderful.

Another danger is that people who are scared of things in groups often create what's called mass sociogenic illness. This is a well-documented phenomenon where when people believe that something is going to make them ill, they actually start to feel symptoms. So the information that gluten is dangerous, and the prevalence of people going gluten free, actually contributes to a form of mass sociogenic illness where people come to experience symptoms from eating food when in fact those symptoms are entirely psychosomatic.

You've looked quite deeply at the ways in which a number of different foods have been villainized over the years, how those demonizations have ebbed and flowed. What is your take on the staying power of the gluten free movement? How much bigger will it grow, and how long will it persist?

Once you have doctors writing popular fear mongering books, it is incredibly difficult to unring the alarm bell. I think our collective fear of gluten will last a really long time. It takes a while for science sometimes to disprove things, so it will likely be a long time until we will have sufficient evidence to show that people are or are not correct about their gluten sensitivity.

The other thing I would say is that the gluten free movement recapitulates many of the myths that underlie lots of diet fads. People argue that gluten is something modern, and therefore is something scary. People argue that we need to go back to a more natural past. I think this is something else that's really important when we think about gluten. Today, especially, people are having a crisis of authenticity. No one wants to feel artificial. Gluten has been cast as a modern creation, as something that takes away from authentic natural foods, and people are afraid of eating it because they don't want to become what they eat. Gluten has come to represent something artificial, something modified. I think there's going to be an incredible staying power to the idea that if you avoid gluten you can also avoid artificiality and foods that we are not meant to eat.

Anything else you want to add? This is where you get to take everything back!

I think it's really important that people understand that I'm not arguing that non-celiac gluten sensitivity doesn't exist. What I'm arguing is that responsible science doesn't fearmonger when we are currently uncertain about something. Of course there is a chance that 20 years from now, all of the celebrities and the celebrity doctors will prove right, and gluten really will be the villain so many people think it is. That's possible. But it's still irresponsible to talk about it that way right now. Getting ahead of the science, spreading fear and alarm before we actually know the truth endangers society, threatens culinary culture, and makes for irresponsible science.

Too many times in the past, we have gotten dietary villains wrong. We're all sick of hearing this back and forth on whether we should eat cholesterol or not, on whether we should eat fat or not. So when people say, 'hey what's the harm?' it's really important that they think about how frustrating it is to have been wrong about all these things in the past, and how grateful we should be to science for being slow and humble before it makes pronouncements about what we should and shouldn't eat, pathologizing the foods that we love, and ruining our ability to sit down and eat dinner in peace.

Gluten free-diets are trendy, but are they healthy for everyone? ASAP Science explains. (ASAP Science)