The growing popularity of gluten-free foods is obvious to anyone who's been in a supermarket lately.
The aisles are loaded with dozens of gluten-free products, ranging from breads, cakes and cookies to pastas, soups and even vitamins.
In fact, new research shows that sales of gluten-free foods could top $8.8 billion this year. That's up 63 percent from 2012, according to the report from Mintel, which analyzes consumer and product data trends.
And while the number of adults who say a gluten-free lifestyle is good for anyone, and those who view it as just the latest fad, are about evenly split at 41 percent and 44 percent, respectively, 22 percent of Americans follow a diet free of gluten - a protein found in wheat, barley and rye - the group reports.
And that's up from 15 percent just last year.
But is the added expense of these products - which were 242 percent more expensive than their conventional counterparts according to one National Institutes of Health study - worth it?
There's no doubt a gluten-free diet can help people with potentially life-threatening wheat allergies or Celiac disease, a painful and damaging intestinal condition caused by gluten, according to experts.
But for those with what's called gluten sensitivity - a condition marked by varying degrees of intestinal distress and sometimes other symptoms as well - the jury is still out.
"In our practice, we've seen an increasing number of patients coming to us with a gluten-restricted diet that they've settled on on their own, probably because of reading about it on the Internet," said Dr. Jonathan Markowitz, a pediatric gastroenterologist with Greenville Health System's Children's Hospital.
"But for people who don't have Celiac disease or a documented wheat allergy, it is controversial," he added. "I suspect that at the rate these sales are going up, a lot of people are not taking it for Celiac disease but for kind of a presumed sensitivity to gluten."
Experts say there isn't enough scientific research about gluten sensitivity to say for sure whether it's a real condition. "There are a lot of people who think they're gluten sensitive. And I think it's a possibility," said Dr. Matthew Wood of Asheville Gastroenterology Associates, an affiliate of Mission Health in Asheville. "But the data right now is equivocal."
"It's not clear that gluten sensitivity exists in and of itself. We don't know for sure," adds Markowitz. "When my patients come in and say, 'I stopped taking gluten and I feel better,' I believe them. But I don't know why they feel better. Is it gluten or something else?"
A study in the journal Gastroenterology, for instance, seems to point to FODMAPs as causing the irritable bowel type symptoms, he said.
FODMAPs are "fermentable, oligo-, di-, monosaccharides, and polyols," according to the research, or short-chain carbohydrates like fructose and galactose. And they're common in foods that also contain glutens, such as some fruits, grains and breads, and are hard to digest, Markowitz said.
"This article highlights why a gluten-free diet may be doing several other things at the same time that could affect symptoms independent of whether the gluten is there or not," he said. "When people remove gluten, they are also removing FODMAPs. And it might be FODMAPs that are the culprit."
"There may be some benefit to limiting gluten, but also a benefit to limiting FODMAPs," he said. "There's an entire spectrum of FODMAPs that patients can have difficulties with."
Because some people may be more sensitive to sugars like fructose, which are found in fruits, both doctors recommend the FODMAPs diet as the first line of therapy for people with irritable bowel syndrome.
And Wood says he always wants patients who think they have a gluten sensitivity be tested to be sure they don't have Celiac disease.
"We have patients who say they feel better after being on a gluten-free diet, but I'm always very concerned they may have Celiac disease," he said. "And we want to make sure they're treated aggressively (if that's the case) and monitored for other diseases that can occur with Celiac."
Wood said he also works closely with a nutritionist to sort out what's in a patient's diet that may not be agreeing with him.
Another thing doctors are learning more about these days is that any significant change in diet alters the bacterial makeup in the intestines, and can result in similar symptoms, Markowitz said. "The most important take-home from that study to me is that A, our diet is very integrally involved with how we feel, and B, when you change the diet and you think you're changing one thing, but you may be changing something else," he said.
Antibiotics can also play a role by causing temporary distress while they're being taken, Markowitz said.
In addition, he said, antibiotics can permanently alter the intestinal bacteria in children, potentially leading to problems when they become adults. And it's common for children to be on antibiotics at some point, for an ear infection, for example.
It's possible all of it could be tied in to gluten sensitivity, he said.
But in the end, Markowitz said that since there's no inherent danger to a gluten-free diet, he doesn't tell his patients to stop it. He just advises people to be careful and not make assumptions about things that haven't been proven and that the medical literature question.
"At the end of the day, as a physician, I want my patients to feel better. And if they feel good and are happy and not putting themselves at any particular risk, that's OK," Markowitz said. "They may be hurting their wallets, but not their physical being.