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Do Carbs Kill Your Brain?

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carbs brain fog, carbs and the brain
Could the carbs in that banana be contributing to brain fog? iStock.com/IgorDutina

Recently, I’ve been hearing from many patients who have read Dr. Perlmutter’s new book, Grain Brain, and are now concerned about their carb intake. In his book, Dr. Perlmutter suggests that dietary carbohydrates cause high blood sugar, inflammation, and other effects that lead to a “toxic brain,” which can then develop into neurological conditions such as Alzheimer’s, Parkinson’s, depression, and others. Based on this line of causality, he recommends that everyone consume a very low carb diet (<60g per day) in order to prevent neurological disease.

First of all, I’d like to point out that very low carb (VLC) and ketogenic diets can be effective therapeutic tools for treating many neurological disorders. I touched on this briefly a while back in my podcast with Emily Deans, and initial studies on low-carb diets and mental health have shown promise. (1, 2, 3, 4) Because Dr. Perlmutter is a neurologist, it makes sense that he would be a proponent of low-carb diets for his patients based on these therapeutic effects.

Does eating carbs destroy your brain and lead to neurological disease?

However, recommending a low-carb diet as an intervention for sick people is very different from promoting it as a preventative measure for the entire population, which is what Dr. Perlmutter does in Grain Brain. His approach would be somewhat akin to recommending that everyone go on the Autoimmune Protocol to prevent autoimmune disease, which would be unnecessarily restrictive and unhelpful. It’s important to realize that just because a low-carb diet can help treat neurological disorders, doesn’t mean the carbs caused the disorder in the first place. While I don’t argue with the idea that refined and processed carbs like flour and sugar contribute to modern disease, there’s no evidence to suggest that unrefined, whole-food carbohydrates do. In fact, there are three compelling reasons why this is not the case.

#1 – We Evolved Eating Whole-Food Carbohydrates

The first reason it doesn’t make sense that carbohydrates cause neurological disorders is that we’ve been eating carbs for a very long time, and we’re well adapted to digesting and metabolizing them. For instance, fruit has been part of the human diet for longer than we’ve been recognizably human, and while starch hasn’t been part of the human diet for quite as long, it’s clear that we’ve evolved mechanisms to digest and utilize it efficiently.

Compared with most primates, humans have many more copies of the gene AMY1, which is essential for breaking down starches. (5) This gene is unusual in that the number of copies varies greatly between populations, with more copies present in populations that consume more starch. This indicates that starch played a significant role in our evolution, and some scientists have even argued that consumption of starch was partially responsible for the increase in our brain size.

In addition to possessing the ability to break down complex carbohydrates, our bodies require glucose to function properly and maintain homeostasis. The fact that humans can produce glucose from protein is often used as an argument that we don’t need to eat glucose, but rather than viewing this as evidence that that glucose isn’t important, we might view it as evidence that glucose is so metabolically essential that we evolved a mechanism to produce it even when it’s absent from the diet.

#2 – There Are Many Traditional Cultures with High Carb Intake and Low or Nonexistent Rates of Neurological Disease

If carbohydrates cause neurological disorders, one would expect to see high rates of dementia and similar diseases in populations where carbs constitute a significant portion of the diet. But as it turns out, many of the cultures that maintain the lowest rates of neurological and other inflammatory disease rely heavily on carbohydrate-dense dietary staples. For example, the Hadza of north-central Tanzania and the Kuna of Panama obtain a high percentage of their total calories from foods that are high in natural sugars, such as fruit, starchy tubers and honey, yet they are remarkably lean, fit and free of modern disease. (6, 7)

Other examples include the Kitava in the Pacific Islands, Tukisenta in the Papa New Guinea Highlands, and the Okinawans in Japan. The Kitavan diet is 69% carb, with a high reliance on starchy tubers such as yams, and sugary tropical fruits such as banana and papaya. (8) The Okinawan diet is even more carb-heavy at 85% carbohydrate, mostly from sweet potato. (9) Finally, the Tukisenta diet is astonishingly high in carbohydrate at over 90%. (10) All of these cultures are fit and lean with practically non-existent rates of neurological disorders and other modern chronic disease. (11)

#3 – Modern Research Does Not Support the Notion That ‘Safe’ Carbs Are Harmful

The claim that carbohydrates from whole-food sources cause neurological disorders is not supported by anthropological evidence. In addition, modern studies on the health effects of carb-dense foods such as fruit also fail to support Perlmutter’s hypothesis. In fact, studies overall suggest that eating whole, fresh fruit may actually decrease the risk of health issues such as obesity and diabetes, and that limiting fruit intake has no effect on blood sugar, weight loss or waist circumference. (12, 13)

As you may know if you’ve been following my website, there is plenty of modern research demonstrating that diets rich in refined and processed carbohydrates are harmful. However, this is not due to carb content alone, and there’s no evidence that whole-food carbs have the same effect. When an author or expert recommends excluding or severely limiting one of three macronutrients that humans consume, the evidence demonstrating harm should be strong—not only because of the inconvenience of following such a restricted diet, but because extreme diets (ketogenic or VLC diets in this case) are not always harmless. In my practice I’ve seen many patients who’ve worsened on long-term VLC diets, including those with adrenal issues and poor thyroid function. Long-term VLC diets can also lead to imbalances in gut bacteria due to a lack of prebiotic fiber, which can result in digestive issues.

As I’ve always maintained, you need to find out what works for you and tailor your diet to your specific health goals, rather than follow a canned approach. This is exactly what I’ll teach you to do in my book, Your Personal Paleo Code (published in paperback as The Paleo Cure in December 2014), which is coming out at the end of December.

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846 Comments

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  1. One part of the vegetarian myth is that growing crops is more sustainable than raising meat.. That may not be true at all. In fact mono-cropping, growing on crop on a parcel of land like corn etc is destroying the ecosystem. It wipes out all natural life in that field except for the one plant.
    It is estimated that there will be no topsoil left in about 40 years,
    Left to nature, most fields in North America would return to grass land. We could then graze beef and bison and other animals on their natural food which is grass. We can then rotate them out and bring in other animals like chickens. Rotate them out and the grass quickly grows back because it has been well fertilized by these animals and we rotate back in the beef. Stir..repeat.
    Where this has been done, the birds come back, the insects come back the critters come back.
    Search Your Tube for Polyface farms.. They are the most productive farm acre for acre in the Shenandoah Valley.

    • So Polyface farms is always being held up by everyone as, THE MODEL of sustainable animal agriculture. Yet few people who revere them seem to be aware of one little important fact:

      Polyface is not able to provide for all those animals using just the resources grown on that farm — they import a lot of feeds that are grown other places.

      Check out the book, Meatonomics for the rest of this story!

  2. Oh my, Tom! The horror of it all!

    Hey, man, didn’t you hear? I’m a suit-wearing exec from the grain society? lol

    Get some therapy.

    I, for one, don’t push carbs and grains. Just like Chris, I am saying that there is no proof that carbs and grains do harm to nearly all of society.

    In fact, these are a vital part of many people’s diet, as I mentioned before.

    Oh, but you’re right. In fact, hospitals and doctors’ offices are filling up with the sick and dying as we speak.

    The Chinese, the oldest nation to eat carbs and grains are quickly dying off. . ..

    The hundreds of millions of people around the world are dropping like flies. . .

    Get a clue, brainstorm.

  3. There is some very suspicious misinformation being posted on this site. Since the forum is unmoderated, there isn’t much that can be done about it.

    But I would warn anyone reading this to beware of two posters who are posting almost daily. It is easy to identify them because they post constantly and because they seem to have no interest in discussing Grain Brain or the issues Perlmutter raises. They are only interested in pushing a particular (pro-grain, pro-carb) point of view. I would not be surprised if they are being paid to do this or if they have some personal or financial interest.

    I would not pretend to know whether Perlmutter is right or wrong, but he is scientifically substantial, he is anything but a quack, and the science he discusses in his book is very real. The two people who are constantly posting against Perlmutter and against low-carb do not ever offer any real science (other than citing things like “common sense” and grain industry and bakery p.r.) They do seem to be intent on out-posting everybody else. They should be ignored.

  4. Hello, I want to Share a book for the grain brain readers who are brainwashed (excuse the pun) into thinking that ALL carbs and wheat is bad for EVERYONE.

    It’s called the “Drain Brain.”

    Now showing at a bookstore near you.

    • Keep an eye out for my new book “Carrot Catastrophe” it discusses the ravages caused by eating carrot. Already those who have read the book and gone off carrots are reporting that they feel incredible. Brain fog has lifted, adrenals are functioning again, their bodies once ravaged by acidosis are now completely alkaline, energy levels have returned. Beware the carrot.

    • you need to get informed. Permulter is not against all carbs? he is against processed carbs (grains) and fruit is ok in moderation. Cruciferous vegetables contain low levels of carb but are very healthy for the gut and he is pro these. Stop banging on about China they are not the first people to eat carbs and their health is nothing to write home about in any case! We never ate grains for the first 2.5 million years of existence only introduced 10,000 years ago!

  5. I personally have noticed an improvement in my mood since adopting some of Perlmutter’s dietary suggestions. I respectfully ask anyone who feels incited to become insulting and abusive in an otherwise calm, rational discussion to carefully consider the possibility that their diet may be contributing to the way they feel.

  6. Chris you say that glucose is so important, that we have evolved a way of making it in the body, if it isn’t part of our diet. Why, then, haven’t we evolved a way to supply protein, if it isn’t part of our diet?

  7. Well think of it this way: If carbs are so bad for us, why aren’t the hospitals and cemeteries filled to the rim?

    Why is it that the biggest carb-eating nations are healthier than us???

    Think about it.

    Use your common sense, don’t make eating complicated–and the best of luck to ya! 🙂

    • Thanks – and same to you. I know what you’re saying. I don’t want to spend too much time obsessing over just what to eat and supplement. I know what you mean.

    • Not so much carbs are bad for us, but too many carbs are bad for some of us, especially fast acting carbs. The cemeteries would be filled to the brim if it were not for medical intervention, think about diabetes, in its many forms, if it were not for insulin injections,where else would they be, but in a grave.

    • Perry wrote: “Well think of it this way: If carbs are so bad for us, why aren’t the hospitals and cemeteries filled to the rim?”

      That is a straw man argument. I think Perry displays a fundamental miss undestanding of the case against eating too many carbs ,

      No one is saying that carbs are a poison.. You dont eat some and then get very ill or drop dead on the spot. Carbs are not arsenic.

      And there is a proper way to eat some carbs, in the form of vegetables, especially leafy green ones. But starchy foods are to be avoided..

      Plus, the advice to lower carb consumption is not isolated. The other end is that we must eat far more healthy fats. Low carb diets without the right fat intake is also not the very best thing for people.

      Once again, keeping your insulin elevated too much above what a low carb diet will affect has been shown to shorten life and create all kinds of health conditions ..Period

      And yes, the hospitals are full up with people sick from a diet too rich in carbs and too low in fat. .

  8. Debbie, when I lost 31 pounds of pure fat, I made sure to have as many nutrients in my diet as possible. It helps the body lose weight.

    Plus, when you eat less food, you need to choose foods that have the highest nutrients.

    Sweet potatoes are loaded, I mean, LOADED with nutrients.

    It’s also a great comfort food–and comfort foods can also help you lose weight.

    The more mentally satisfied you are, the easier the diet is.

    Not to mention you need carbs for muscle and brain energy.

    During my diet, a lot of the times I would have a bowl of oatmeal or a sweet potato with a four-ounce chicken breast.

    You can go as high or as low as you want on the carbs–whatever works for YOU.

    I ate and still eat 300+ carbs a day.

    Carbs aren’t the evil doers…

    it’s the overall calories.

    Just watch the overall calories, your protein and the necessary nutrients–and move more.

    That’s all there is to it, basically.

    • Thanks so much for these responses. Perry, you’re right, and your advice pretty much correlates with what I do. At this point, I’m fine tuning according to what I believe might be the healthiest way to eat for me – but there are contradictory views on what that is (Grain Brain vs. Perfect Health Diet), and even the extensive testing that is available is far from definitive, and practioners also disagree as to treatment.

      So, I assume we all check out the blogs we respect – Chris Kressler I respect more than any other – and try to adjust what we learn to our situations.

      I’d like to lose weight, but when I go below where I am now begin to feel extremely low energy. None of this is simple I already eat a fairly low number of nutrient dense calories per day – I’m probably where I should be, or even a little low – and I’m not skinny.

      I’m not sure about the carbs, even nutrient dense “safe starches.” Thanks for the feedback!

    • sweet potato is great but grains are not nutient dense. In fact they are very low in bioavailable nutients. All processed foods are nutrient deficient but high in calories.

      • Grains sound so evil right? What do these Harvard guys know anyway compared to a guy trying to sell books?

        ———

        A growing body of research shows that returning to whole grains and other less-processed sources of carbohydrates and cutting back on refined grains improves health in myriad ways.

        As researchers have begun to look more closely at carbohydrates and health, they are learning that the quality of the carbohydrates you eat is at least as important as the quantity. Most studies, including some from several different Harvard teams, show a connection between eating whole grains and better health.

        Cardiovascular Disease

        Eating whole instead of refined grains substantially lowers total cholesterol, low-density lipoprotein (LDL, or bad) cholesterol, triglycerides, and insulin levels. Any of these changes would be expected to reduce the risk for cardiovascular disease. In the Harvard-based Nurses’ Health Study, women who ate 2 to 3 servings of whole-grain products (mostly bread and breakfast cereals) each day were 30 percent less likely to have a heart attack or die from heart disease over a 10-year period than women who ate less than 1 serving per week. (1) A recent meta-analysis of seven major studies showed that cardiovascular disease (heart attack, stroke, or the need for a procedure to bypass or open a clogged artery) was 21 percent less likely in people who ate 2.5 or more servings of whole-grain foods a day compared with those who ate less than 2 servings a week. (2)

        Type 2 Diabetes

        In a study of more than 160,000 women whose health and dietary habits were followed for up to 18 years, those who averaged 2 to 3 servings of whole grains a day were 30 percent less likely to have developed type 2 diabetes than those who rarely ate whole grains. (3) When the researchers combined these results with those of several other large studies, they found that eating an extra 2 servings of whole grains a day decreased the risk of type 2 diabetes by 21 percent.

        More recent findings from this study (the Nurses’ Health Studies I and II) and the Health Professionals Follow-Up Study suggest that swapping whole grains for white rice could help lower diabetes risk: Researchers found that women and men who ate the most white rice—five or more servings a week—had a 17 percent higher risk of diabetes than those who ate white rice less than one time a month. Those who ate the most brown rice—two or more servings a week—had an 11 percent lower risk of diabetes than those who rarely ate brown rice. Researchers estimate that swapping whole grains in place of even some white rice could lower diabetes risk by 36 percent. (4)

        Cancer

        The data on cancer are mixed, with some studies showing a protective effect and others showing none. (5) A large, five-year study among nearly 500,000 men and women suggests that eating whole grains, but not dietary fiber, offers modest protection against colorectal cancer. (6, 7)
        Digestive Health

        By keeping the stool soft and bulky, the fiber in whole grains helps prevent constipation, a common, costly, and aggravating problem. It also helps prevent diverticular disease (the development of tiny pouches inside the colon that are easily irritated and inflamed) by decreasing pressure in the intestines.

        Staying Alive

        An intriguing report from the Iowa Women’s Health Study linked whole-grain consumption with fewer deaths from noncardiac, noncancer causes. Compared with women who rarely or never ate whole-grain foods, those who had at least two or more servings a day were 30 percent less likely to have died from an inflammation-related condition over a 17-year period. (8)

        How Do Whole Grains Improve Health?

        Whole grains don’t contain a magical nutrient that fights disease and improves health. It’s the entire package—elements intact and working together—that’s important.

        The bran and fiber in whole grains make it more difficult for digestive enzymes to break down the starches into glucose. Soluble fiber helps lower cholesterol. Insoluble fiber helps move waste through the digestive tract. Fiber may also kindle the body’s natural anticoagulants and so help prevent the formation of small blood clots that can trigger heart attacks or strokes. The collection of antioxidants prevents LDL cholesterol from reacting with oxygen. Some experts think this reaction is a key early step in the development of cholesterol-clogged arteries. Phytoestrogens (plant estrogens) found in whole grains may protect against some cancers. So might essential minerals, such as magnesium, selenium, copper, and manganese. These minerals may also help reduce the risk for heart disease and diabetes. And then there are the hundreds of substances that haven’t yet been identified, some or many of which may play as-yet-undiscovered roles in health.

        http://www.hsph.harvard.edu/nutritionsource/what-should-you-eat/health-gains-from-whole-grains/

  9. Without doing extensive texting I’m currently confused as to how low or high to go with consuming carbs. Other than that, I’m very happy with my current diet. Because I have a long history of metabolic derangement – eating disorders, obesity, bulima – and am now for the past 25 years maintaining an 80 pound weight loss, I wonder if I should automatically restrict my carbs more than I am. I currently eat a good amount of sweet potato and butternut squash, and wonder if that’s not a great idea for me. I enjoy eating a late dinner and then becoming sleepy and pretty much falling asleep. I don’t know how bad that is…

    • People vary in their tollerence and ability to digest carbs/starch.. If you are maintaining your weight, sweet potato is a fine choice because it does not spike up your insulin very hard. If you feel stronger with it in your diet, then I would continue… But if you need to lose some weight, drop the sweet potatoes for a while.

      To maintain most people eat about 50 to 100 carbs per day.. To drop weight keep your carb intake to 20 or less… Unless… you are carb senstive. I need to keep carbs to 20-30 per day just to maintain… Anything more than that and I put on lbs. You should go trail and error to find the right level of carbs for you.

    • Lose the butternut squash, sweet potato and other high carb foods. You’ll feel better and be less sleepy after dinner. I’d also eat earlier in the evening to unburden your gut before going to bed. Trial and error seems to be in order. Good luck!

      • Three square meals with the biggest meal at the end of the day may not be what we are most adapted to. Meal timing is an interesting subject. A larger protein and fat rich breakfast may provide enough energy for you to last until late afternoon without needing a “Lunch” break.

        • Yeah, but eating a large breakfast just isn’t what I enjoy. I’m not ready to sacrifice that, I admit it.

        • Debbie,

          If you want to eat what you like (within reason and whole foods) just intermittent fast. It improves all health markers and increases longevity (plenty of research out there). Basically for females eat in a 10hr window and fast for 14hrs straight (for 14 just water). If you want, take it up to 16hrs fast. Or you can do 5:2 diet, eat what you want for 5 days, then fast 2 days in a row (max 600 calories per day). Google the BBC Horizons documentary ‘Eat, Fast and Live Longer’ it’s fascinating! When IF catches on I think most health blogs and supplement companies will go out of business, it’s that simple and beats any ‘diet’ plans out there. Diet bloggers and diet authors should be worried.

      • I agree with you about the timing of dinner, but I just don’t want to eat earlier, I admit it. Just not willing. About the carbs, that’s the issue we’re discussing here. I don’t think there is a definitive answer for me yet. Thanks, though for the feedback.

  10. Not a darn thing, Pam. 🙂

    But when he, and others say that grains and carbs are bad for everyone–and they don’t use any common sense–that is something else.

    Good luck with it.

  11. I am currently reading the Grain Brain and although I feel some of the advice on elimination of 90% of all grains and sugars seem out of the norm, it is well known that most of our grains are genetically modified which I believe is more the problem and causing reactions in the human body. I found that I was gluten sensitive a year ago after participating in a cleanse – when adding gluten back to diet, an immediate mental response of anxiety, brain fog resulted. This is before I had any pre-conceived notion about the harms of gluten. However, after I experienced this, I began to learn of gluten’s harmful effects on people that are sensitive. I still battle a slight depression problem, but not as bad as before. I may not follow the Brain Grain book to the letter, but I intend to give the plan a try and see how it works for me – what is the harm in that?

  12. Do your research. You’ll be surprised by what you’ll discover–and how much their lifestyles have actually changed.

    • Perry,

      You mentioned you were a writer for a health company. You should have this information at your fingertips. Why not post some links here?

      Besides you keep missing the point. The point is you keep changing your own arguments. Like trying to nail jello to a wall.

      “China is one of the leading pasta eaters, dating back to before Christ was born. Look up their health stats.

      “The Unites States is among the unhealthiest because of all the sugars, processed foods and dirty oils that fast-food is cooked in. ”

      Remember that post you made? Here you are trying to contrast China with the US. You are implying the Chinese were healthy, while the US is not. You had an opportunity to admit the Chinese were not exactly healthy, but you didn’t make the case.

  13. The traditional Chinese diet is high fat and low sugar with few processed foods. It’s not because of the rice and noodles that they do well, it’s in spite of this. Eating enough animal fat is the key

  14. “The health of the Chinese is declining..”

    With more and more of them eating junk carbs, in the past decade or so, along with the U.S. bringing in their franchise restaurants…it’s no wonder.

    Their parents, grandparents, great grandparents, and so on who all ate healthy carbs and grains, would be shaking their head in disappointment at their poor eating habits.

    Plus, the Chinese of today are a hell of a lot less active, and spoiled due to their now successful economy and building boom.

    They are a perfect example on what can happen very quickly when a nation becomes less active and eats crap carbs, along with crap food in general.

    • You’re like a shifting target, always changing your argument and the facts to get ahead. First the Chinese eat lots of “pasta” and are very fit, then now they eat junk carbs and that’s why they are getting sick. *shakes head* Ok I get it. You’re one of those people who can’t stand to lose a point in a debate, and so when facts are presented, you backpedal and pretend that’s what you were arguing all along. Maybe you need to add “Perry Backpedal” to your list of aliases.

  15. Okinawa’s also eat lots of sweet potatoes, which does not spike insulin all that much. Plus, they had a famine at the end of the War which may have killed off the less hardy. Sweet Potatoes + Pork and fat+ vegetables and some fish is a fine diet. Add in good genetics and lots of being outside in the air and sun and we shouldn’t be surprised at their longevity..

  16. I am reading the book and find some very fascinating findings with facts and research that support the concepts. I think that What Kris Kresser raises balances perspective. As I am reading the book, it definitely challenges the common practices that have been taught over the past 30 years.

    A family member of mine died from complications of Alzheimer, it was a terrible, painful and long time. That person was doing all the things the doctors told that person to do (statens, heart medication, antiswelling medication, stay away from eggs, use canola oil and carbohydrates are ok). What David Perlmutter raises explains at a biochemical level how the carbohydrates and medications will damage the brain. He builds a very compelling case and educates on the way the body functions that so far when I fact check, they are true.

    However, I still think there is a balance. Still working on that.