High-Carb Diet May Increase Your Risk of Dementia

High-Carb Diet

Story at-a-glance -

  • Chronically higher blood sugar levels have a profoundly negative influence on your thinking, even in people without type 2 diabetes
  • Research suggests even if you’re healthy, keeping your blood sugar levels lower than what is typically considered "normal" is best for your brain health
  • A high-carb diet is not only detrimental because of its impact on insulin and leptin levels but also due to gluten
  • Gluten makes your gut and even your brain more permeable, which allows proteins to get into your bloodstream that would otherwise have been excluded; this sensitizes your immune system and promotes inflammation and autoimmunity
  • One of the best dietary strategies to protect your brain health is reduce (non-vegetable) carbohydrate consumption, including sugars and grains, while increasing healthy fat consumption

By Dr. Mercola

If you're interested in protecting your brain health and preventing dementia, including Alzheimer's disease, the research is pouring in in support of a key dietary strategy… namely, avoiding sugar and carbohydrates, including gluten.

Last year, I interviewed Dr. David Perlmutter—probably the leading natural medicine neurologist in the US, from my perspective—whose New York Times best-selling book, Grain Brain, has brought this issue to the forefront of medicine.

He recently expanded on this topic in an interview in Alternative and Complementary Therapies,1 where he cites even more research showing a high-carb diet may be detrimental to your brain.

Higher Blood Sugar Levels Are Bad for Your Brain

According to recent research published in Neurology, chronically higher blood sugar levels have a profoundly negative influence on cognition, which the researchers believe is "possibly mediated by structural changes in learning-relevant brain areas."2

One of the most important aspects of the study, however, was that these negative effects occurred even in people without type 2 diabetes, which suggests even if you're "healthy," keeping your blood sugar levels lower than what is typically considered "normal" is probably still best for your brain health. The researchers noted:

"…strategies aimed at lowering glucose levels even in the normal range may beneficially influence cognition in the older population."

This isn't entirely surprising, as separate research has found that impaired insulin response was associated with a 30 percent higher risk of Alzheimer's disease,3 and overall dementia and cognitive risks were associated with high fasting serum insulin, insulin resistance, impaired insulin secretion, and glucose intolerance.

However, the new study and another published last year4 suggest higher blood sugar levels may be detrimental to your brain even if you don't have any of the former conditions.

It's becoming increasingly clear that the same pathological process that leads to insulin resistance and type 2 diabetes may also hold true for your brain. As you over-indulge on sugar and grains, your brain becomes overwhelmed by the consistently high levels of insulin and eventually shuts down its insulin signaling, leading to impairments in your thinking and memory abilities, and eventually causing permanent brain damage.

High-Carb Diet May Increase Your Dementia Risk by 89 Percent

In one of the most striking studies on carbohydrates and your brain, researchers revealed that those who consumed higher amounts of carbs in their diets had an 89 percent increased risk of dementia. As for those whose diets were highest in fat… their risks decreased by 44 percent.5 Dr. Perlmutter says:6

"We live with this notion that a calorie is a calorie, but at least in terms of brain health, and I believe for the rest of the body as well, there are very big differences between our sources of calories in terms of the impact on our health.

Carbohydrate calories, which elevate blood glucose, are dramatically more detrimental to human physiology, and specifically to human health, than are calories derived from healthful sources of fat.

The diet that I recommend—high in fat and low in carbohydrates—has simply been what we have eaten for a million years, so it has a bit of a track record. The notion that this is a revolutionary new diet has to be put into context. In reality, the diet that people are now consuming.

This is dreadfully high in carbohydrates and low in fat, as our governmental institutions are recommending, is the biggest challenge to human physiology that we have ever experienced, and this is very, very worrisome."

One of the reasons why a high-carbohydrate diet is so damaging is due to fructose. You may already know I am passionate about warning of the dangers of refined fructose.

There is NO question in my mind that regularly consuming more than 25 grams of fructose per day will dramatically increase your risk of dementia and Alzheimer's disease. Consuming too much fructose will inevitably wreak havoc on your body's ability to regulate proper insulin levels.

Research also shows that rats fed fructose syrup showed significant impairment in their cognitive abilities—they struggled to remember their way out of the maze. They were slower, and their brains showed a decline in synaptic activity.

Their brain cells had trouble signaling each other, disrupting the rats' ability to think clearly and recall the route they'd learned six weeks earlier.7 There is another component of a high-carb diet that may be equally as damaging, however.

Click here to learn moreClick here to learn more

Gluten Sensitivity May Also Harm Your Brain

Dr. Perlmutter stresses that gluten sensitivity is involved in most chronic disease, including those affecting your brain, because of how gluten affects your immune system. Unfortunately, many people, physicians included, still believe that if you don't have celiac disease or digestive symptoms, gluten is fair game and you can eat as much of it as you like.

Full-blown celiac disease, which is an extreme form of immune-mediated gluten sensitivity primarily affecting the small intestine, affects an estimated 1.8 percent of people in Western cultures. But non-celiac gluten sensitivity may actually affect as much as 30 to 40 percent of all people, and according to Dr. Alessio Fasano at Massachusetts General Hospital, virtually all of us are affected to some degree.

This is because we all create something called zonulin in the intestine in response to gluten. These difficult to digest proteins known as prolamines, found in wheat, barley, and rye, make your gut more permeable, which allows undigested proteins to get into your bloodstream that would otherwise have been excluded. That then sensitizes your immune system and promotes inflammation and autoimmunity.

According to Dr. Perlmutter, much of our current disease burden stems from the fact that we are contaminating our immune systems with proteins to which the human immune system has never, in the history of humankind, been previously exposed to. I believe another major factor is the development of genetically engineered (GE) grains, which are now pervasive in most processed foods sold in the US.

These GE crops create proteins never before encountered in any natural grain or food, so GE grains deliver a double whammy against your immune system. Food allergies clearly appear to be one of the most noticeable side effects of a GE-grain diet. Dr. Perlmutter explains the role of gluten in brain health:8

"In terms of gluten consumption, we have come a long way from our understanding that celiac disease exists, and we now recognize that, according to top researchers, non-celiac gluten sensitivity also exists, which may affect 30% of humanity. Marios Hadjivassiliou [MD, department of neurology, Royal Hallamshire Hospital, Sheffield, United Kingdom] has said, so poetically, that gluten sensitivity may at times be a pure neurologic disease that is basically extraintestinal, and that we do not need to have intestinal issues to define gluten sensitivity. In fact, we are now seeing literature that points the finger clearly at gluten sensitivity as a culprit in a variety of neurologic problems, including depression, cognitive dysfunction, seizures, and even headaches."

Your Brain Needs Healthful Fats

High-carb diets have yet another downfall and that is there tendency to be low in beneficial fats – a ratio that has been supported by "official" dietary guidelines that vilified fats for decades. According to Dr. Perlmutter, our current dietary fat phobia "has absolutely been the cornerstone of our most common degenerative diseases of the day, including Alzheimer's." Why? Because when you cut dietary fat and keep protein about the same, you're going to fill in the gaps with health-harming carbohydrate foods, predominantly grains.

Beneficial health-promoting fats that your body—and your brain in particular—needs for optimal function include organic butter from raw milk, clarified butter called organic grass fed raw butter, olives, organic virgin olive oil, and coconut oil, nuts like pecans and macadamia, free-range eggs, wild Alaskan salmon, and avocado, for example. Dr. Ron Rosedale first mentored me in the importance of insulin resistance and a moderate protein (and therefore high fat) and low-carb diet. Most low-carb advocates were very accepting of, if not promoting, high protein, and protein was, and still is, often recommended as a replacement for the carbs.

However, a high-fat, low-carb diet is very different than a high-protein, low-carb diet and this is a major source of confusion by both the public and researchers when doing studies and publishing conclusions. Dr. Rosedale believes the average amount of protein recommended for most adults is about one gram of protein per kilogram of LEAN body mass, or one-half gram of protein per pound of lean body weight. (As an example, if your body fat mass is 20 percent, your lean mass is 80 percent of your total body weight.) In short, most people consume too much low-quality protein and carbohydrates, and not enough healthy fat. The key is to eat high-quality natural fats, and a lot of them. Dr. Perlmutter expands:

"…the quality of the fat that we consume is absolutely fundamental. When we're saying high-fat diet, we're not talking about prepared foods on the Twinkie aisle at the grocery store that contain modified trans fats; hydrogenated fats that are clearly coffin nails. They're a great risk for brain disorders, heart disorders, diabetes, etc. We're talking about these beautiful, natural fats that we have been consuming for more than two million years."

Tipping the Scales Toward a Healthier Brain

Alzheimer's disease, the most common form of dementia, is the sixth leading cause of death in the US. This fatal and progressive condition destroys brain cells, resulting in memory loss and severe thinking and behavioral problems (aggression, delusions, and hallucinations) that interfere with daily life and activities.

It's one of the most feared diseases because there is currently no cure… but there are steps you can take toward prevention. Your brain is not "programmed" to shrink and fail as a matter of course as you age. We now know that every activity in which you engage—be it exercise, the foods you eat, the supplements you take, your personal relationships, your emotional state, your sleep patterns—all of these factors dramatically influence your genetic expression from moment to moment. And this, in turn, influences your overall health and risk of disease, including in your brain.

Lifestyle strategies that promote neurogenesis and regrowth of brain cells include the following. All of these strategies target a specific gene pathway called BDNF or brain-derived neurotrophic factor, which promotes brain cell growth and connectivity as demonstrated on MRI scans. So if you're looking for the most straightforward way to lower your risk of dementia, including Alzheimer's, this is the plan to follow. As you'll notice, a great deal of the plan involves modifying your diet to lower unhealthful carbs and increase healthful fats:

  • Reduce (non-vegetable) carbohydrate consumption, including sugars and grains.
  • Increase healthy fat consumption.
  • Increase your omega-3 fat intake and reduce consumption of damaged omega-6 fats (think processed vegetable oils) in order to balance your omega-3 to omega-6 ratio. I prefer krill oil to fish oil here, as krill oil also contains astaxanthin, which appears to be particularly beneficial for brain health. As explained by Dr. Perlmutter, astaxanthin is very "focused" on reducing free radical-mediated damage to fat, and your brain is 60-70 percent fat. Personally, I believe there is very compelling evidence to supplement with 12 mg of astaxanthin to prevent Alzheimer's.
  • Exercise. Physical activity produces biochemical changes that strengthen and renew not only your body but also your brain—particularly areas associated with memory and learning.
  • Reduce overall calorie consumption, including intermittent fasting.