“Stop eating carbs and you can control your destiny and avoid Alzheimer’s,” promised Dr. Mehmet Oz on his TV show in 2013. “Eating carbs eats away at your brain.”
His guest: David Perlmutter, neurologist and author of the bestselling book Grain Brain.
“Dementia: Is Gluten the Culprit?” ran the headline in a 2014 interview with Perlmutter on Medscape (part of WebMD). Much of his argument wasn’t about gluten per se. It was about the dangers of high blood sugar.
“If you have too much blood sugar, your brain begins to die,” warned Dr. Oz. “It shrinks. It shrivels up.”
Perlmutter gave more details to Med¬scape. “The data show that individuals with lower blood sugar levels have a lower risk for dementia,” he explained.
True. A 2013 study reported that people with even slightly elevated blood sugar levels have a higher risk of dementia.
But are grains to blame? Clearly, extra pounds are the major cause of high blood sugar levels. It doesn’t matter if that spare tire comes from eating carbs or fat. After all, pizza, burritos, sandwiches, fries, cookies, pastries, ice cream, and many other foods have both.
But Perlmutter never mentions cutting calories. He only cares about cutting carbs.
“If you look at the A TO Z trial, which was published in JAMA in 2007,” he told Medscape, “dramatic reductions in blood sugar were seen in participants on a lower-carb, higher-fat diet.”
True. But the same reductions were seen in people on the other weight-loss diets in the A TO Z trial. (The trial tested a lower-carb, higher-fat Atkins diet, a lower-fat, higher-carb Ornish diet, and two others.)
Perlmutter also points to DIRECT, “an interventional trial demonstrating both weight loss and reduction of fasting blood sugar in individuals eating a higher-fat, lower-carbohydrate diet.”
True. But, once again, in the DIRECT trial, all three diets (lower-carb, lower-fat, and Mediterranean) reduced blood sugar levels.
What if you’re not losing weight, like the people in the DIRECT and A TO Z trials?
“If you’re eating a high-carb diet, cutting carbs would reduce blood sugar levels throughout the day,” says Frank Sacks, professor of cardiovascular disease prevention at the Harvard School of Public Health.
But he’s not talking about Perlmutter’s advice to replace nearly all carbs with fats, including saturated fats like butter and red meat. Sacks is talking about eating a Mediterranean or DASH-type diet, which gets a modest amount of carbs from fruits, vegetables, and whole grains (not sugars and white flour) and gets fats from oils, nuts, and fish.
What’s more, Sacks adds, “obesity is by far the biggest cause of high blood sugar and type 2 diabetes.”
And what about gluten, the unfashionable protein in wheat, rye, and barley? That’s also a threat to your brain, says Perlmutter.
“We have to look at gluten sensitivity in a new light, recognizing that its manifestations may extend well beyond the gut,” he told Medscape.
In celiac disease, the body has an autoimmune reaction to gluten that damages the large intestine lining. The most common symptoms—like diarrhea, bloating, gas, and abdominal pain—are due to that damage. Symptoms can also include anemia, fatigue, mouth ulcers, headache, and foggy thinking, but less often.
“Overall, neurological problems related to celiac disease are not terribly common,” says Andrew McKeon, associate professor of neurology at the Mayo Clinic.
And many are nothing like ordinary memory loss. Cerebral ataxia, a balance problem, is the most common. And you’d know it if you had it.
“The easiest way to describe it is that the patient looks like a person who is drunk,” says McKeon. “They slur their speech or they can’t walk a straight line.”
Other problems are also noticeable. “They can include anything from cognitive problems to sensory ataxia, in which the person doesn’t know where they’re standing or sitting in space, so they have a tendency to topple over,” says McKeon. “The array of problems is quite diverse.”
How does gluten cause trouble for people with celiac disease?
One possibility: the damaged gut can’t absorb some nutrients. “Dating back to the 1960s, it was recognized that some patients developed disorders because they couldn’t absorb copper and vitamin E,” explains McKeon.
Another possibility: “Gluten-triggered inflammation somehow gets to the brain and causes neurological problems.”
But it’s not just people with celiac who are at risk, according to Perlmutter.
“Gluten-containing foods stimulate inflammatory reactions in a significant number of individuals, well beyond the 1.8 percent of the population that has celiac disease,” he told Medscape.
Yet McKeon has found no evidence that gluten causes neurological problems in people without celiac.
“There are some reports that patients with ataxia who did not have celiac disease seem to improve or at least stabilize with gluten-free diets,” he notes. “In our own study, we didn’t find that any of those patients improved.”
Is gluten a common cause of Alzheimer’s? “Absolutely not,” says McKeon. “Most people who have cognitive problems in our society have progressive neurodegenerative disorders of unknown cause.”
And they take years to progress. In contrast, most neurological disorders in people with celiac “come on really quickly and progress very rapidly.”
Bottom Line: If you’re like most Americans, you eat too much bread, rice, pasta, sweet baked goods, and other grains. Shoot for just four or five small servings a day. But that’s unlikely to cut your chances of memory loss unless it helps you lose weight or lowers your blood sugar.
Sources: N. Engl. J. Med. 369: 540, 2013; JAMA 297: 969, 2007; N. Engl. J. Med. 359: 229, 2008; Neurol. 83: 1, 2014.
Other relevant links:
• Is there a connection between caffeine and dementia? See: Caffeine and Dementia
• Is there a connection between Alzheimer’s and diabetes? See: Diabetes of the Brain
• Americans need to eat less grains, especially white grains. See: How to Diet: Americans Need to Switch to Whole Grains