You only need to spend 10 minutes in a supermarket these days before noticing that half of the items seem to be marketed as “gluten-free.” Even raisins and nectarines are labeled that way, as if they ever contained gluten in the first place. Is it a fad much like the “fat-free” hype of the ’80s?

Maybe.

But based on my own experience eliminating gluten from my diet, and the stories of people who struggle with chronic depression that I’ve read in the online forums I participate in, I believe the stuff can be toxic to your mood, especially if you have a sensitivity to it.

While only 1 percent of the U.S. population has celiac disease (where eating gluten triggers an autoimmune response that damages the intestines and keeps nutrients from being properly absorbed), many more may be living with non-celiac gluten sensitivity. For these folks, consuming even a small amount of gluten (a protein found in wheat, barley, and rye) causes digestive problems, drops in energy, and symptoms of depression and anxiety.

“[Gluten and dairy] are the main allergens and foods that cause bad brain reactions,” writes Mark Hyman, MD, in his best-seller The Ultramind Solution. “Stopping these foods can be life-changing for the majority with brain and mood problems.”

Gluten and Depression

A small study published in Alimentary Pharmacology & Therapeutics in May 2014 demonstrated the psychological effects of gluten on people with self-reported non-celiac gluten sensitivity. In this study, 22 participants ate a gluten-free diet low in FODMAPs (fermentable oligosaccharides, disaccharides, monosaccharides, and polyols) for a three-day baseline period, and then received one of three dietary challenges (supplemented with gluten, whey, or placebo) for three days, followed by a three-day minimum washout period before starting the next diet.

Researchers assessed the participants at the end of the study using a psychological tool called the Spielberger State-Trait Personality Inventory (STPI). People in the study who consumed gluten had higher overall STPI depression scores compared to those on the placebo diet.

The high correlation between celiac disease and depression is also telling in regards to gluten’s effects on mood. One study published in 1998 in Psychiatric Quarterly determined that about one-third of those with celiac disease also have depression. Another study published in April 2007 in the Journal of Affective Disorders evaluated approximately 14,000 people with celiac disease and found that they had an 80 percent higher risk of depression. Swedish researchers reported in August 2011 in Digestive and Liver Disease that the risk of suicide was moderately higher in people with celiac disease.

Gluten and Schizophrenia

The first research into how gluten impacts the brain and could lead to psychiatric problems occurred more than 60 years ago with groups of schizophrenic patients. In a study published in January 1966 in The American Journal of Clinical Nutrition, researchers calculated the numbers of women admitted to mental hospitals in Finland, Norway, Sweden, Canada, and the United States from 1936 to 1945, and the consumption of wheat and rye during the same period. They found a significant positive correlation between the increase in average annual admissions for schizophrenia in each country and the increase in consumption of wheat or wheat and rye. The reverse was also true; as gluten grain rations decreased so did the rate of first-time admission to psychiatric institutions.

There is an increasing volume of research associating gluten consumption to schizophrenia, such as the study published in September 2013 in the The World Journal of Biological Psychiatry that found elevated levels of antibodies to the gluten protein gliadin in people with schizophrenia. Researchers compared the anti-gliadin antibodies of 950 adults with schizophrenia to those of 1,000 healthy controls. The odds of having anti-gliadin antibodies was 2.13 times higher in schizophrenics, indicating the possibility of an adverse reaction to wheat proteins among this population.

In a study published in January 2011 in Schizophrenia Bulletin, researchers discovered that people with schizophrenia have higher than expected antibodies related to celiac disease and gluten sensitivity.

How Gluten Affects the Brain

So what is the link between gluten and psychiatric disorders? How might wheat impair the brain? That’s what I find most fascinating.

In 1979, Christine Zioudrou, PhD, and her colleagues at the National Institute of Mental Health found that gluten contains polypeptides, or protein fragments, that are able to bind to morphine receptors in the brain — the same receptors that the polypeptides in opiate drugs bind to. They dubbed them “exorphins,” short for exogenous morphine-like compounds, distinguishing them from the endorphins (also morphine-like compounds) that we produce internally and occur, say, during a runner’s high. These receptor sites impact the degree of pleasure and reward we feel and, because of the withdrawal effect, alter brain chemistry. They can have a distinct effect on mood.

According to William Davis, MD, author of Wheat Belly, researchers speculate that exorphins might be the active factors in wheat that caused the deterioration of schizophrenic symptoms in a famous study led by F. Curtis Dohan, MD, during his time at the Veteran’s Administration Hospital in Coatesville, Pennsylvania. “Wheat, in fact, nearly stands alone as a food with potent central nervous system effects,” Dr. Davis writes. “Outside of intoxicants such as ethanol (like that in your favorite merlot or chardonnay), wheat is one of the few foods that can alter behavior, induce pleasurable effects, and generate a withdrawal syndrome upon its removal.”

The Gut-Brain Connection

In people with celiac disease, gluten causes intestinal dysbiosis, a condition in which the gut bacteria are out of balance. As I’ve written about before, gut bacteria can certainly impact mood — so much that our gut is sometimes dubbed our second brain. In some people, gluten could also erode the gut lining when certain foods enter our bloodstream: Our immune system, responding to an attack by a foreign object, sends an SOS message through our nervous system, which can generate symptoms of anxiety and depression.

Basically, gluten triggers inflammation, and the response to that inflammation can affect different organs and tissues, all of which impact mood. A damaged intestinal wall also means that we are not properly absorbing essential nutrients, especially those critical to mood, like zinc, the B vitamins, and vitamin D.

Finally, if our intestines are unhealthy, that means we’re not manufacturing as much serotonin, since 80 to 90 percent of serotonin is produced in our gut nerve cells. Gluten could also limit the production of tryptophan, an amino acid that is the precursor of serotonin.

I eliminated gluten from my diet two-and-a-half years ago and noticed a substantial improvement in my mood — but it didn’t happen instantly. It took as long as nine months to reap all the benefits. Now that I’m gluten-free, I’ve become much more sensitive to it and can feel its effects almost immediately: anxiety, brain fog, and death thoughts.

Fad or no fad, I’m a believer in gluten-free!

Originally posted on Sanity Break at Everyday Health.