Dangers of Zero-Carb Diets, I: Can There Be a Carbohydrate Deficiency?

It’s frequently said in the Paleo blogosphere that carbs are unnecessary. Here’s an example from Don Matesz, an outstanding blogger who eats a diet extremely close to ours:

Protein is essential, carbs are not…. You can only cut protein so much, but you can cut carbs dramatically.

Dr. Michael Eades has mocked the idea of a carbohydrate deficiency disease:

Are there carbohydrate deficiency diseases, Mr. Harper, that you know about that the rest of the nutritional world doesn’t?  I’ll clue you in: there aren’t.  But there are both fat and protein deficiency diseases written about in every internal medicine textbook.

Such statements made an impression on me when I first started eating Paleo five years ago. But several years and health problems later, I realized that this view was mistaken.

Why Aren’t Carbohydrate Deficiency Diseases Known?

How do doctors discover the existence of a nutrient deficiency disease?

It’s not as easy as you might think. For example, the existence of essential fatty acid deficiency diseases in humans was in doubt right up into the 1950s, even though omega-6 deficiency disease had been discovered and characterized in rats in the 1920s. [1] The reason is that omega-6 and omega-3 deficiencies can occur only on unnatural diets. It was infants fed fat-free formula in the 1940s and 1950s who ended up proving the existence of omega-6 deficiency disease in humans.

Two difficulties have made it challenging for science to recognize a carbohydrate deficiency syndrome:

  1. Lack of an animal model.
  2. The rarity of zero-carb diets among humans.

Until recently, few people save the Inuit ate very low-carb diets, and the Inuit didn’t leave good medical records. As a result, few or no humans developed recorded carbohydrate deficiency syndromes.

This wouldn’t be a problem if it were possible to induce carbohydrate deficiency in animals. However, it isn’t.

Animals don’t get carbohydrate deficiency diseases because they have small brains, meaning low glucose needs, and big livers, meaning high glucose manufacturing capacity. Animals can generate all the glucose they need from protein or from volatile acids like propionate produced by bacterial fermentation in their digestive tracts.

But, as we note in the book, humans are more fragile. We have small livers and big brains, and so the possibility of glucose deficiency is real.

Here is a comparison of brain, liver, and gut sizes in humans and other primates [2]:

Organ % body weight, humans % body weight, other primates
Brain 2.0 0.7
Liver 2.2 2.5
Gut 1.7 2.9

The brain is the biggest determinant of glucose needs.  While other primates need only about 7% of energy as glucose or ketones, humans need about 20%.

Compared to other primates, humans have a 12% smaller liver. This means we can’t manufacture as much glucose from protein as animals can. Humans also have a 40% smaller gut. This means we can’t manufacture many short-chain fatty acids, which supply ketones or glucogenic substrates, from plant fiber.

So, while animals can meet their tiny glucose needs (5% of calories) in their big livers, humans may not be able to meet our big glucose needs (20-30% of calories) from our small livers.

So any carbohydrate deficiency disease will strike humans only, not animals.

How Should We Look for a Carbohydrate Deficiency Disease?

To find a carbohydrate deficiency syndrome in humans, we should look at populations that eat very low-carb diets, such as:

  • The Inuit on their traditional hunting diet.
  • Epilepsy patients being treated with a ketogenic diet.
  • Optimal Dieters in Poland, who have been following a very low-carb diet for more than 20 years.
  • Very low-carb dieters in other countries, who took up low-carb dieting in the last 10 years as the Paleo movement gathered steam.

We should also have an idea what kind of symptoms we should be looking for. Major glucose-consuming parts of the body are:

  • Brain and nerves.
  • Immune system.
  • Gut.

The body goes to great lengths to assure that the brain and nerves receive sufficient energy, so shortfalls in glucose are most likely to show up in immune and gut function.

So, we’ve mapped our project. Over the coming week, or however long it takes before we get tired, we’ll investigate the evidence for carbohydrate deficiency conditions in humans.

Related Posts

Other posts in this series:

  1. Dangers of Zero-Carb Diets, II: Mucus Deficiency and Gastrointestinal Cancers A Nov 15, 2010.
  2. Danger of Zero-Carb Diets III: Scurvy Nov 20, 2010.
  3. Dangers of Zero-Carb Diets, IV: Kidney Stones Nov 23, 2010.


[1] Holman RT. The slow discovery of the importance of omega 3 essential fatty acids in human health. J Nutr. 1998 Feb;128(2 Suppl):427S-433S. http://pmid.us/9478042

[2] Aiello LC, Wheeler P. The expensive tissue hypothesis: the brain and the digestive system in human and primate evolution. Current Anthropology 1995(Apr); 36(2):199-211.

Leave a comment ?


  1. Tyler,

    The video by Dr Li is in this post, page down to the TED talk.


  2. Hi Tyler,

    Both the carbs and the turmeric would have helped in 2009. Fish oil is good for general health, at least in moderation, but probably not for this particular condition.

    I recommend a pound of salmon/sardines/anchovies/herring per week and no fish oil.

    Sugar does feed fungi, but (1) the main concern is internal infection and blood sugar is regulated, so eating carbs doesn’t raise blood sugar much; (2) the immune response to fungi requires glucose and is downregulated if you don’t eat carbs; and (3) on very low-carb dieting you’ll generate ketones which is an even better food for fungi than sugar.

    Overall, you’ll do better with a systemic Candidiasis if you eat more carbs.

    Perry, thanks for providing the link!

  3. “One possibility to consider: don’t exclude oral pathogens. Rice digestion starts in the mouth, with salivary enzymes, and it’s possible sugars in the oral cavity trigger acne.”

    Does rice syrup, potatoes or other tubers digestion start in the mouth aswell? So could different safe starches effect differently on acne and which would be the safest?

  4. Hi jnv,

    Yes. Saliva contains amylase which breaks down starch into sugar. It will act on longer sugars & polysaccharides and so will tend to digest potatoes and to reduce rice syrup polysaccharides to shorter simpler sugars. This may increase availability to oral bacteria.

    However, I don’t think the sugars stay long in the mouth compared to the digestive tract so my guess is this is a less important pathway.

    I think the best thing is to well-chew one’s food and mix it thoroughly with saliva to aid digestion.

  5. Paul,

    You wrote, “The water-soluble parts of the garlic are the good parts, the other parts can irritate and inflame your gut.”

    I have been experimenting with adding very large amounts of minced raw garlic to my mashed starches. I was inspired to do so because, while I am still not sure what general class of infection I have, let alone what specific pathogen(s), I know that many herbalists consider raw garlic to be one of the best, broadest natural antibiotics there is. Notably, allicin is the cornerstone of Zhang Qingcai’s treatment for Lyme and coinfections.

    But I am trying to heal my gut simultaneously. My gut is likely leaky, as there is no doubt that my dramatic recent deterioration was triggered by food.

    What you have written raises concern that all of this garlic is counterproductive. Could you elaborate?

    (I am happy to switch to garlic tea, but I actually enjoy the taste of the garlic with my starches; furthermore, one frequently hears that garlic is far more effective raw.)

    Thanks for your time.

    • Hi MM, Garlic is a great antimicrobial and often this is a big help overcoming gut problems. But we can’t ignore possible toxic effects on human cells.

      As usual in dealing with gut problems, you have to experiment and see whether it’s helping you. I cautiously approve of garlic for gut problems.

      Hi tom,

      Yes. They’re the same thing.

  6. off-topic for this thread, but can you answer a quick question: Is coconut butter just as valuable as coconut oil?

  7. Hi Paul,

    You mentioned that the brain prefers glucose to run on, and I agree that most people seem to function well with carb intake.

    But I thought that the brain prefers protein to run on, given that it was meat (possibly also seafood) that caused the human brain to grow in size. From Mark Sisson “Easy to digest meat and fat made our big brains possible” and Michael Eades “Increasing the amount of easily-digested food of animal origin allowed us to shrink our guts while expanding our brains”.

    Did our ancestors grow their brain primarily from protein or tubers/starch? I wouldn’t be surprised if starches played some role since humans did make quick advances in technology and culture not long after the Neolithic era coming hand in hand with increased cereal starch consumption.

    • Hi Pete,

      The brain does not run on protein. Protein has to be converted to glucose in order to feed the brain.

      The brain can run on glucose or ketones.

      Our ancestors ate a mix of foods, but their diets were high in fat and included tubers/starch.

      • “Our ancestors ate a mix of foods, but their diets were high in fat and included tubers/starch.”

        ***Hi Paul. Q: How much and how often did our ancestors eat starch? What resources are you using to support this statement?

        Many of our ancestors ate no starch and virtually no carbohydrate at all as you know.

        • Hi Fred,

          Nearly all Paleolithic and Mesolithic sites contain residues of starch consumption. The Inuit are basically the only known exception. Modern hunter-gatherers all cultivate, gather, or trade for starches. I estimate the Paleolithic diet at about 20% carbs but most anthropologists believe it was higher than that.

  8. Hi Paul,

    I like to share my experience with you. I am a normal weight male in my twenties. I saw Dr. Terry Wahls video and I liked the idea of eating this way. So I tried it.

    I was doing 30-45min weightlifting and around 1 hour cycling usually 4 times a week and even when I was eating fruit, but no starch, I started to notice that my mouth was dry every morning when I woke up. Then I found out that fructose might be bad and just like you, I removed fruit one month later from my diet.

    I was then eating very low carb. I usually ate 4 times a day, sometimes 5. Bacon and eggs almost every day and lot of salmon. Chicken, beef and pork few times a week. Beef liver once a week. I always included green leafy vegetables, tomatoes, cucumbers, carrots and sometimes other vegetables. After I removed fruit I started to feel worse almost immediately. Mouth was completely dry during the night and I had very dry nose. Constipation was a big problem. I could not sleep normally anymore, I was waking up around 3-4AM, probably because cortisol was very high and maybe adrenaline as well and I could not fall asleep after that. I felt that my testosterone was very low, because I had no libido. My body temperature was low.

    I went to my family doctor and had the usual morning fasted blood work done. I asked my doctor to measure cortisol, testosterone, T3 and rT3 as well, but unfortunately my doctor said that I need to see a specialist for that. Before paleo style eating my lipids, HbA1c and etc. were in the “normal” ranges. After experimenting with low carb paleo my results were: triglycerides 148(over the normal range in my country), HDL 51 was good, and LDL 219 and cholesterol 331 were extremely high. My doctor said that my good HDL value saved me from a statin. I found your site and it answered all my questions. High cholesterol and LDL were most likely because of low T3. I ate some safe starches and fruits after I took the blood test and I was able to sleep very well, mucus and libido was back the next day. Constipation went away.

    Glucose deficiency can occur and I think especially if you are exercising more than an average person.

    Thank you for all the information!

    Good luck defending safe starches at the AHS!

    • Simply –

      Were you drinking alcohol?
      Were you eating too little fat?

      It is never seen in RCT studies that triglycerides RISE on a low carb diet.

      How long were you doing VLC for?

      • I am facing the exact problem: waking up 2AM and can´t sleep no more. No will to do exercise. Any weight loss (even some gain). I don´t drink alcohol and eat plemty of good fats. I´m goijg to pt some carbs (rice pasta) in my diet, it can be any other thing.

        I also eat lots of vegetables, eggs, red grass fed meat and all of that good paleo things. I think my problem really it´s lack of carbs.

  9. Excat scenario, with the exception that I became too tired to continue my workout.

    I am always a bit curious about sophisticated people, such as yourself, that don’t just run their own labs through Life Extension, because they send you to your local lab and then e-mail you the results. This is private and off the radar. Once a year all labs are half price.

    Don’t let the system hold you hostage to the point where they call all the shots.

    If you were not a “truth seeker” you could go to scores of physician appointments and never find your answer, IMO.

  10. Does alcohol worsen the effects of hypoglycemia?

  11. Back in 1971, nine obese men who were fasted for a minimum of 60 days (yikes!) and then administered insulin boluses to the point that blood glucose levels were as low as 0.5 mmoles/liter (9 mg/100 ml) yet they failed to exhibit hypoglycemic reactions. Sounds like the brain’s requirement for glucose is much lower than we believe.


  12. Hello, Paul!
    I am at the beginning of the Diet, I am from Russia, normal-weight girl of 22. But all my life i have been keeping diets (with periodical failures) – low-carb, low-fat, vegetarian…
    Now i feel that The Diet is very good for me. it’s so tasty! i used not to allow these priducts. But.. I eat lots, lots of protein and fat!! I hope it’s just beacause of insuline, becuase i have eaten a lot of sugars lately. (PHD only for 4 days).
    I hope I will be able soon to say to myself “stop” after 200g of meat and 20g of fat each serving…

  13. Hola Dr. Jaminet

    ¿cuando el libro Perfect Health diet en español? 🙂

  14. Hello Dr. Jaminet,

    When I´m counting my carbs to reach an optimum for perfect health diet, and I´m supplementing fibres (inulin, pectine, oligofructose, larch arabinogalactan) and ribose, do the fibres and polysaccharides count to the carbs?

  15. Hello Dr. Jaminet,
    Thank you very much for your reply, I understand. In your book you write how to treat neurological issus and about the amount of carbs and protein for these diseases, thank you. I have candida and parasites (which my doctor treates naturally) and therefore carb intolerance. I have to build up my carb amount slowly. I´m supplementing potatoe starch, fermentable fibres and glyconutrients.

    To reach your suggested carb-calories: may I count more starchy vegetables like onions, carots, radish, fennel and noodles to my carb calories?

    For the amount of no starchy vegetables like salade, tomates etc. I would substract 50 cal/pound for digesting, as you suggested. For the more starchy and sweet vegetables I substract no carb calories of my daily carb intake plan.

    Many thanks Eva

  16. I went on a low carb diet, 15g a day with lots of coconut oil, spinach, fatty meats, greens and nuts. I tried carb back loading and felt like crap. I went on the potato diet to try and flip the switch but i was getting huge adrenaline rushes, i have no energy and wake up feeling very weird and unwell. How can i eat carbs again? My blood sugar foes down after a meal. And i have intense adrenaline rushes. Have i ruined my metabolism, what can i do? Rose

  17. As you recommended Don I watched Don’t eat bread because it turns to fat?
    Don Matesz makes a wrong argument I think, like ingested fat converts directly to far tissue. Disappointed. Your opinion?

  18. Hello!
    I am a type 2 diabetic diagnosed two years ago and i have since eaten only a strict Low Carb, High Fat diet. I have felt pretty good, i need no medecines such as insulin for glucose control. But, i have recently felt like my eyes have gone very dry upon waking up from sleep, sometimes painfully dry. I have also noticed sudden bouts of complete loss of strenght, it only lasts for a fraction of a second while holding a glass of water for example, so i almost drop it. My hands just goes numb for a microsecond. Never experienced this before and im desperately trying to make this diet work. I eat lots of broccoli and meats, some tomatoes, cucumber, a lot of cheese and some fatty 40% cream as sauces for meals. I have lost about 21 kilos so far and im at a steady weight, neither loosing nor gaining. but being T2 diabetic its …so so very important to make a low carb diet work otherwise i dont know what to do, being a insulin junkie will kill me in the long run, i cant take that path…

    • Hi John,

      You need to add some carbs back in. Include some starch and some fruit/beets. That will probably fix the dry eyes.

      I’m not sure what’s behind the loss of strength. That’s neurological and you should discuss it with your doctor. Probably nutritional deficiencies are a major contributor, so you should compare your diet to PHD and figure out what is missing.

      Best, Paul

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  21. Salvatore Esposito

    “The body goes to great lengths to assure that the brain and nerves receive sufficient energy, so shortfalls in glucose are most likely to show up in immune and gut function.”

    What are the immune functions that are influenced by glucose deficiency?

    I’m so curious about this…

    • Salvatore,
      Try putting your question into the site search box (upper right of the page).

      I used your text and found many links to previous discussions of similar topics.

      I searched on: immune functions that are influenced by glucose deficiency.

      Hope this helps.

      • Salvatore Esposito

        Thanks Randy.

        When I put your query in the search box it appears lots of sites, all on diabetics effects, but I’m looking for about a deficiency of glucose and its effect on immune system.

        I can’t use search box only to find the artcles of this site.

        However thanks again.

        • Salvatore, Did you put the query into the search box at the top right of the Perfect Health Diet home page? NOT a general GOOGLE search. For me it looks like a box outlined in blue and inside it says google enhanced search. That allows a google search over just the content of the PHD site. The first few links might be something like paid advertisements but the rest are from the PhD site.

        • Also, at the bottom of the fist page, note the faint grey numbers: 12345678910

          Those are clickable links to additional pages of search results.

          Lots of discussion related to you interest, all fro PHD site.

  22. Hi Paul,

    I would be interested in your thoughts on this…

    I have huge oxalate and salicylate issues and the carnivore/zero carb diet is working wonders for me.


    • Hi Andy,

      First, I love that group at Tel Aviv University. Miki Ben-Dor is a friend of PHD and his blog is worth reading, see http://www.paleostyle.com/?p=2212 for a post directly discussing the work referenced in that article.

      I think it’s absolutely right that humans were apex predators and were responsible for extinctions of large mammals in most of the world outside Africa; in Africa human selective pressure led to herding and other evolutionary changes enabling large mammalian species to survive human predation.

      However, the jump from humans eating a lot of animal food, and getting most calories from animals, which I think is true, to exclusively eating animal foods I think is unwarranted.

      Best, Paul

      • Thanks for the reply, Paul.

        Do you not think the simplicity of it makes perfect sense? 95% of the worlds flora being toxic to humans and to the flora that are supposedly beneficial to humans so much needing to be done to it to make the nutrients either bioavailable or non-toxic (cashews for example).

        Whereas 95% animal products can be eaten raw and the nutrients are instantly bioavailable and won’t harm humans (bar trying to catch them/kill them in the first place).

        If you were out in the wilderness, it would be a much safer bet to swerve plant foods completely (as the probability is the plant will either make you very ill or worse by eating it) whereas you can eat most meat products either raw or cooked and it will be very beneficial to you.

  23. Very interesting. I have lots of histamine problems, too. I read only yesterday that Thiamin (Vitamin B1) destroys histamine. I’m trying to find info on that. Wouyld you know anything about it?

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