Americans are increasingly adopting a gluten-free diet, spurred by claims that avoiding gluten might cure various ailments or even prevent diseases such as Alzheimer’s and dementia.
Eliminating gluten is typically recommended for people with celiac disease, a condition where the small intestine’s ability to absorb nutrients is inhibited by the gluten protein. Incidences of celiac disease are rising in the U.S.—a 2012 study from the Mayo Clinic found that the number of U.S. adults with the disease has increased four-fold over the last 50 years, with about 1 percent of adults currently affected.
The reasons for the increase are not entirely understood, but one unintended consequence is clear to anyone who has walked down the aisles of a grocery store recently, where there is a “gluten free” label on everything from boxes of crackers to milk cartons. The idea that gluten-free is healthy and may even prevent everything from headaches to Alzheimer’s has spread rapidly, championed by celebrity doctors including Dr. Mehmet Oz and Dr. David Perlmutter, a Florida physician and author of the 2013 book Grain Brain: The Surprising Truth About Wheat, Carbs and Sugar — Your Brain’s Silent Killers. In a 2013 survey conducted by the Food Marketing Institute, only 2 percent of shopper respondents said they bought gluten-free foods because they had a celiac sensitivity; 59 percent said they simply believed gluten-free foods to be healthier.
Yet researchers who study gluten and celiac disease caution that if you don’t have the condition, it would be wise to steer clear of this fad, which bans everything from beer to bagels.
“We don’t take the decision to start a gluten-free diet lightly,” says Dr. Benjamin Lebwohl, an assistant professor of epidemiology at Columbia University Medical Center who focuses on outcomes in celiac disease.
“It’s a difficult and expensive and socially isolating diet,” and when it comes to using it as a preventative measure for diseases other than celiac, the science just isn’t there, he says.
Experts further warn that questionable claims are being made by people who stand to benefit lucratively.
One of the most controversial of gluten-free proponents is Dr. Perlumtter, whose Grain Brain book is on the New York Times bestseller list and has been published in 17 countries. The book argues that eating foods with high glycemic indexes, which happen to be some of the most gluten-rich foods, increases the chances of developing neurological disorders like Alzheimer’s and dementia.
The book’s prescription of a gluten-free diet relies in part on recent studies showing that some people without celiac disease have neurological responses to gluten, including migraines, “brain fog” and trouble controlling their muscles, and that high glucose levels, which may be caused by a number of things from diabetes to stress to diet, may be correlated with dementia.
In an interview, Dr. Perlmutter said the point he is making is that “lifestyle choices affect the brain” and emphasized that he does not view a gluten-free diet as a silver bullet.
The impact of changes in diet and exercise on brain health has been “left out” of much of the public conversation about disease prevention, says Dr. Perlmutter, so the idea that people could have some control over the trajectory of their brain health is empowering for many.
Grain Brain cites various studies to make its case. One is a case series of 13 patients conducted by the Mayo Clinic in 2006 that showed a potential association between gluten and dementia. However, the researchers noted that the study was small, their results did not display a causal relationship, and that more research was needed to determine the nature of the association.
Dr. Perlmutter points to another study released in January from the Journal of Neurology, Neurosurgery and Psychiatry which found that a Mediterranean-style diet that is higher in omega-3 fat and lower in carbohydrates than the typical American diet dramatically improved cognition.
But many researchers aren’t sure that science has reached the point where connections can so confidently be drawn between diet and cognitive health.
Dr. Paul K. Crane, a co-author of one of the cited studies, which was published last August in the New England Journal of Medicine, worries that Dr. Perlmutter is one of a growing group of public figures stretching the findings of a study to fit a cure-all narrative.
The problem with Dr. Perlmutter and other gluten-free proponents is that they sometimes extrapolate diet advice from studies that do not directly relate to the research questions the authors set out to answer, says Dr. Crane, an associate professor at the University of Washington’s department of medicine with a special interest in Alzheimer’s disease and cognitive functioning.
His paper describes a potential link between high blood glucose levels over time and dementia. It did not discuss whether the high blood glucose levels in his subjects were connected to eating gluten-rich foods with high glycemic indices, which tend to cause a short-term jump in blood glucose. This didn’t stop the media and other researchers from reporting that the study was making recommendations for a low glycemic diet, which Dr. Crane himself refuses to make.
“I think a lot of these links are awfully speculative, and a lot more research is needed,” Dr. Crane says.
Last fall, a group of European doctors also championed a low glycemic diet based on a study they published in the journal Neurology. The study found that adults with high blood sugar levels had a smaller hippocampus volume and more memory problems than those with lower blood sugar. However, the doctors studied glucose levels, not glycemic index impact, Dr. Crane points out.
“Their exposure data was pretty similar to my exposure data, [which was] not at all about glycemic indices in the diet,” Dr. Crane says..
In fact, very little research has been done on the relationship between glycemic indices and neurological problems, and scientists have not determined the impact of multiple swings in blood glucose levels during a single day on dementia risk.
While there is better evidence to suggest that exercise is more effective than diet in staving off dementia, Dr. Crane thinks that the media views exercise as boring.
“You can’t sell walking.”
Dr. Armin Alaedini, an assistant professor of medical sciences at Columbia University Medical Center who studies the links between bacterial and dietary proteins and the development of immune processes, has also seen his findings stretched to tout the gluten-free diet as a preventative measure.
“There is very little data to suggest that gluten proteins interact directly with the brain,” said Dr. Alaedini, who has studied the impact of gluten proteins in patients with autism and schizophrenia. But that has not stopped commentators who reviewed his articles from claiming otherwise.
“I noticed articles talking so definitively about a role for gluten for which we really didn’t have that kind of evidence,” he said.
However, there is evidence that some patients with and without celiac disease exhibit neurological issues, with one of the most common being “gluten ataxia,” or difficulty moving the limbs after consuming gluten. While this is hard to ignore, researchers aren’t sure that gluten proteins themselves are causing the neurological symptoms, according to Dr. Lebwohl. For those with a gluten intolerance, such symptoms could potentially be caused by a failure to absorb vitamin B-12, which plays a key role in brain functioning.
“In those who have celiac disease, the management decision is clear: they need to go on a gluten-free diet. In those who don’t have the disease, it’s still very tempting, and I often agree with going on a strict gluten-free diet to see what happens to neurological symptoms,” Dr. Lebwohl says But “on the other side of things, the more common neurological symptoms a lot of people report…the reason for that is completely unknown at this point.”
For instance, a study by Dr. Lebwohl and others of migraine headaches in people with gluten intolerance found no meaningful correlation between the severity of migraines and the duration of a gluten-free diet.
Ultimately, experts agree that not enough is known about the way gluten impacts the brain—or even whether restricting gluten may negatively impact people without celiac disease—to support a gluten-free diet as a preventative measure for any disease, let alone dementia.
“Even though it makes for a great story, it doesn’t make for great science,” Dr. Alaedini said.
Edited by Elaine Meyer