Do Carbs Cause Dementia?
I am becoming more and more skeptical of reports, best selling books, diet plans, and dietary supplements that claim to be the magic bulletin to cure all. Carbohydrates, better known as carbs, are now responsible for a series of ills including dementia which has become as feared in the United States as cancer.
“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.” The guest on his show when he made this claim was Dr. David Perlmutter, neurologist and author of the bestselling book Grain Brain. Dr. Perlmutter produced a program based on his book for PBS’s December 2014 pledge drive. He is a very convincing and emotion speaker, but I took what he said with skepticism. His theory, like the Paleo Diet theory, is removing all refined carbohydrates (wheat flour and sugar) from the human diet forever.
Dr. Perlmutter backs up his hypothesis with several published research studies, but as I’ve said before research studies can be manipulated to give whatever outcome you want. The American media loves headlines like “Butter is Back”, “Carbs Cause Dementia and Alzheimer’s”, “High Sodium Diets Are Healthier”. These headlines are in the news for a few days or weeks and when experts prove they are false receive little if any attention from the media. The Internet has only made the problem worse.
“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 Medscape. “The data show that individuals with lower blood sugar levels have a lower risk for dementia,” he explained.
A 2013 study reported that people with even slightly elevated blood sugar levels have a higher risk of dementia.
But are grains to blame? Studies show extra pounds (body fat) are the major cause of high blood sugar levels. It doesn’t matter if belly bulge comes from eating carbs or fat. Many foods have both carbs and fat.
Best selling authors like Dr. Perlmutter never mention cutting calories. His mantra is cutting carbs especially gluten based carbs.
“If you look at the A TO Z trial, which was published in JAMA in 2007,” Dr. Perlmutter told Medscape, “dramatic reductions in blood sugar were seen in participants on a lower-carb, higher-fat diet.”
That is a true statement. 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.)
Dr. 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.”
Again, that is a true statement. But, once again, in the DIRECT trial, all three diets (lower-carb, lower-fat, and Mediterranean) reduced blood sugar levels.
What If Your Goal Is Not Weight Loss?
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.
But it’s not just people with celiac who are at risk, according to Dr. 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.
There is currently no published evidence that gluten causes neurological problems in people without celiac.
“Overall, neurological problems related to celiac disease are not terribly common,” says Andrew McKeon, associate professor of neurology at the Mayo Clinic.
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: NutritionAction.com, N. Engl. J. Med. 369: 540, 2013; JAMA 297: 969, 2007; N. Engl. J. Med. 359: 229, 2008; Neurol. 83: 1, 2014.