Is Cutting Carbs Bad For Your Brain? A Neuroscientist Explains

Photo: Adrian Cotiga

As the associate director of the Alzheimer’s Prevention Clinic at Weill Cornell Medical College, my work has been focused on rigorous studies of how lifestyle choices shape the health of our brains. Our research extends beyond the concerns of preventing and mitigating Alzheimer’s, into maintaining vital cognitive power over a lifetime.

Of all aspects of lifestyle, perhaps none is as important as diet. The latest research (including my own work) shows over and over that following a healthy diet is powerfully preventive against brain aging and dementia. However, there is a surprisingly wide controversy over exactly what constitutes a "healthy diet."

Depending on where you get your information, you’ll find that eggs are good for you one day and bad the next; sodium is responsible for high blood pressure until it’s not; carbohydrates and fats take turns making you overweight and sick or energetic and healthy. In 2018, everybody is ditching carbs for fat. And if you’ve been in a bookstore or a restaurant or had friends to dinner lately, you’re well aware of the Great American Gluten Panic.

Today, as many as one in three Americans avoids gluten—a protein found in wheat, barley, and rye—thereby eliminating grains and cereals from the diet. They might be trying to lose weight, boost energy, or even treat medical conditions like arthritis, asthma, multiple sclerosis, schizophrenia, and now more recently: dementia.

Why we shouldn't fear gluten when it comes to brain health.

As a neuroscientist with backgrounds in nuclear medicine (aka brain imaging) and nutrition, I’m frequently asked whether gluten is bad for your brain and whether it should be avoided. The short answer is: No, do not fear gluten. From the point of view of those who rely on peer-reviewed science, there is no conclusive scientific evidence of a connection between gluten consumption and cognitive decline or dementia.

Caveat that indeed about 1 percent of the population suffers from Celiac disease (a gluten allergy), and they should continue to avoid gluten. And while estimates vary, another 6 percent of people may have determinable gluten sensitivities, and they should be careful around gluten as well. But for the other 93 percent of us, a gluten-free diet is not only unnecessary but can do more harm than good.

Photo: Calum Lewis

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Why eliminating grains might do more harm than good.

First off, the witch hunt against gluten has led many people to go on low-carb diets. Since fiber comes mostly from grains (besides vegetables and legumes), low-carb diets can be alarmingly low in fiber as well. Among scientists, there is strong consensus that a diet rich in carbohydrates and fiber is crucial for brain health and Alzheimer’s prevention. And while there is nothing yet proved about how gluten can cause dementia, there are conclusive studies demonstrating that the absence of fiber can harm our brains. Fiber deficiencies harm our guts and therefore the population of friendly bacteria in those guts (the microbiome). Given the established connection between gut health and brain health—a topic all its own—a low-fiber diet risks negative long-term effects on the brain, causing brain fog, confusion, and even depression and anxiety.

Looking at centenarians for clues about carbs and longevity.

And let's look at epidemiology: A large body of literature on centenarians (those who are 100 years old or older) shows that they often follow high-carb diets. That’s a strong clue that the relationship between healthy carbs and fiber and the diet and longevity is a largely beneficial one. When we study centenarian diets in detail, we note that over 80 percent of calories in their diet comes from vegetables, fruit, legumes, and complex carbohydrates, such as whole grains, brown rice, oats, and sweet potatoes. These foods are packed with brain supportive nutrients—from B vitamins to a bounty of antioxidants and minerals. They are also a good source of glucose, the main energy source for the brain. Combined with high fiber content to stabilize blood sugar levels, these foods enhance your metabolism, support healthy digestion, and boost the immune system.

The Mediterranean diet is great for the brain—and full of healthy carbs.

Finally, as an Italian and a nutritionist, but most of all as a neuroscientist, I can’t but praise the Mediterranean diet. Above and beyond our overall physical health, its role in brain fitness is substantial. The Mediterranean diet is an unequivocally carb-rich diet high in vegetables, fruit, whole grain cereals, and legumes. A large body of scientific literature shows that people who closely follow a Mediterranean-style diet are not only less likely to develop diseases like diabetes, obesity, and cardiovascular disease but also have reduced risk of cognitive impairment and Alzheimer’s thanks to the diet’s beneficial effects on the brain.

In the end, eliminating gluten and other grains from the diet may well compromise the adequate intake of fiber, healthy carbs, and other brain-essential nutrients. Organic whole-grain foods should be an important component of the diet, especially for anyone reasonably concerned with preventing neurological diseases like Alzheimer’s.

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Your guide to healthy carbohydrate intake.

If you have Celiac disease or are—like about 6 percent of the population, sensitive to gluten—focus on gluten-free grains like rice, amaranth, buckwheat, millet, quinoa, sorghum, and teff. Gluten-free products are often processed junk foods with high sugar and fat content, mixed with artificial coloring and unhealthy additives. There are many poisons that we introduce into our body and brain, but for the vast majority of us, gluten is not likely to be "the one." That said, if you are about to reach for a cupcake, hold on. Let me suggest three rules to eating carbs:

  1. Vegetables and fruits are "carbs," and vegetables should make up half of your plate at any given meal.
  2. Whole grains are in; refined grains are out (white flour, white pasta, and white bread)—especially those from commercial sources.
  3. A generally correct serving size is one slice of bread or 1 cup of cooked grains or pasta per meal.

As a society, we could perhaps spend less time looking to figure out what's wrong with any one isolated nutrient (like gluten) and invest more time and resources into improving people’s overall diets. That means providing people with access to real, wholesome foods, the rigorously reviewed information to understand what those are, and diverse recipes to bring them to life.

This piece is adapted from Brain Food: The Surprising Science of Eating for Cognitive Power, to be published on March 6th, 2018 by Avery/ Penguin Random House.

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