Celiac disease is widely known to cause digestive problems. That's just the tip of the iceberg, according to the book Grain Brain: The Surprising Truth about Wheat, Carbs, and Sugar--Your Brain's Silent Killers, by David Perlmutter. The intestinal difficulties associated with celiac disease are caused by an immunological response triggered by gluten, similar to an allergic reaction but less violent. This response, which leads to inflammation in the gut, can happen elsewhere in the body, too. Inflammation is at the root of many diseases and complications, including, Perlmutter argues, brain decay. Gluten can lead to inflammation in the brain, which Perlmutter believes leads to conditions like dementia and Alzheimer's.

A practicing neurologist, Dr. Perlmutter's experiences with patients, along with medical research he's studied, have led him to piece together a theory behind brain degeneration that's based on a foundation of gluten and high blood sugar. He also argues for the importance of cholesterol to maintaining brain health, and makes a compelling case that cholesterol-lowering statin drugs are bad for the brain.

Grain Brain frequently veers from the brain to other parts of the body that Perlmutter says are damaged by gluten and carbohydrates and of the general dangers of fat avoidance. You may have heard some of these ideas elsewhere; Perlmutter is clearly aligned with the likes of Robert Lustig, a pediatrician who writes of the ills of sugar, and Gary Taubes, one of the first to demolish the idea that dietary fat and cholesterol are responsible for heart disease.

What Perlmutter brings to the table is the idea that gluten teams up with high blood sugar to wreck the brain. The presence of high blood sugar, he explains, causes a reaction throughout the body called glycation, which he describes as "the biological process whereby glucose, proteins, and certain fats become tangled together, causing tissues and cells to become stiff and inflexible, including those in the brain."

In the brain, he explains, "sugar molecules and brain proteins combine to create deadly new structures that contribute more than any other factor to the degeneration of the brain and its functioning...this is made worse when powerful antigens [a substance that triggers an immunological response] like gluten accelerate the damage. "

Glycation can't be entirely avoided, but high blood sugar, as found in diabetics, he writes, exacerbates it. Where blood sugar is high, the brain (and other bodily structures) is constantly bathed in a glycating sugar bath. Recent studies show that having diabetes doubles one's risk of contracting Alzheimer's disease, he points out. The growing understanding of the connection between the two diseases has prompted some researchers to suggest that Alzheimer's be re-labeled "Type-3 Diabetes."

"The origin of brain disease is primarily dietary," he concludes, and not hereditary, as is most commonly assumed. Gluten, by triggering the immune system, causes inflammation in the brain, which encourages the brain's glycation by sugar circulating in the blood.

Perlmutter also presents evidence that some gluten breakdown products are in an endorphin-like class of molecules called exorphins, which are addictive.

We've known since the late 1970s that gluten breaks down in the stomach to become a mix of polypeptides that can cross the blood-brain barrier. Once they gain entry, they can then bind to the brain's morphine receptor to produce a sensorial high. This is the same receptor to which opiate drugs bind, creating their pleasurable, albeit addicting, effect.

This addictive quality of gluten, he writes, can also lead to withdrawal symptoms among those who remove gluten from their diets.

There is a wide spectrum of gluten intolerance in the population, with celiac disease at the extreme end. Perlmutter recommends six markers you can have run on your own blood to determine your level of gluten intolerance. Along with these, not surprisingly, he also wants you to keep track of your fasting blood glucose and insulin levels.

But he could care less about your blood cholesterol numbers. Perlmutter falls into the increasingly populated camp that believes cholesterol does not cause heart disease. The neurologist takes it a step further by arguing that cholesterol is essential to proper brain function. Statins, which are prescribed to lower cholesterol, have been linked to problems with cognitive function. Perlmutter presents recent evidence as to how that might be happening: the lowering of cholesterol levels muffles communication between neurons, and stifles the production of new brain cells.

Statins appear to influence the body's susceptibility to diabetes, as well. One recent, large study he points to "demonstrated an astounding 48 percent increased risk of diabetes among women taking statin medications."

Another way statins could harm the brain is by paralyzing the cells' ability to make Coenzyme Q10 (coQ10), an antioxidant that plays an important role in cellular energy production. Since coQ10 shares the same metabolic pathway as cholesterol, statins block its production as well.

Some of the side effects often listed for statins, Perlmutter writes, "such as fatigue, shortness of breath, problems with mobility and balance, and muscular pain, weakness and atrophy, are related to the loss of coQ10 in muscles and a reduced capacity for energy production. At the extreme, people who experience severe reactions to statins suffer from serious damage to their skeletal muscles."

The book ends with a recipe section, filled with gluten-free, low carbohydrate, high fat meals. In some ways, these manifestations of Perlmutter's dietary protocols read like a sophisticated foodie's Atkins menu, with more vegetables. There are lusty recipes for steak, fish, and other fatty meats, as well as dips, desserts and sauces. But some people might find themselves missing their favorite carbohydrate pleasures, like fruit, not to mention the grain-based likes of pasta and bread. And forget about that chocolate croissant: Perlmutter recommends a diet of 60 grams or fewer of carbohydrate per day, arguing "[W]e can survive on a minimal amount of carbohydrate, which can be furnished by the liver as needed. But we can't go long without fat."

Barely two months after publication, Grain Brain is already a bestseller, and many people are wondering if they should take drastic dietary action in order to save their brains.

The market for gluten-free foods far exceeds the segment of the population with celiac disease. Many people believe they do better, in myriad ways, without gluten in their diet. Some skeptics of the gluten-free thing are quick to dismiss this as people jumping on the latest food fad. Perlmutter, by contrast, believes "We may all be sensitive to gluten from a neurological standpoint." Even if one doesn't test positive for any of his six blood markers for gluten sensitivity, he is still wary of the sticky protein.

Meanwhile, members of another growing segment of eaters are finding they feel better on low-carb diets. In fact, low-carb diets could be considered a craze as well. Low-carb and gluten free-diets are so popular it almost seems inevitable they would combine into a unified theory of dietary wellness.

Not surprisingly, the many dramatic dietary changes Perlmutter advocates are drawing their share of criticism on multiple fronts. Some skeptics have acknowledged that the studies Perlmutter cites are compelling, and raise important questions. But the conclusion that carbs and gluten will team up to glycate your brain into dementia, they say, is premature.

The examples Perlmutter provides from his private practice, they complain, are anecdotal, and used inappropriately in support of his thesis. There are also concerns about negative health consequences of a high-fat, low-carb diet, both in healthy people and for those with specific conditions, like adrenal or thyroid issues. The specific recommendation of 60 or fewer grams of carbohydrate per day has drawn a lot of blowback, including from active people who say it simply isn't enough to sustain their lifestyles.

While people with certain neurological conditions, like epilepsy and muscular dystrophy, often respond very positively to a low-carb, high-fat diet, prescribing it to the population at large may be jumping the gun, critics say. If your blood sugar isn't high, they argue, why avoid carbs? And turning away from whole fruit and whole grains - even gluten-free grains - is more extreme than even a lot of self-identifying low-carbers want to go.

But nobody is disputing the basic premise behind Perlmutter's theory of brain glycation: that gluten triggers an immune response in many people, which can lead to inflammation, which can lead to disease. And the connection between diabetes and Alzheimer's is on firm footing as well, although there remain more questions then answers.

While Perlmutter focuses on the effect of gluten-triggered inflammation on the brain, there are other parts of the body that could be inflamed as well. This is a rapidly changing field, with much research actively being done. For the moment, Grain Brain makes a compelling case for getting a panel of blood markers for gluten sensitivity. If you're sensitive, experimenting with a gluten-free diet is in order. And check your blood sugar.