Dangers of Zero-Carb Diets, II: Mucus Deficiency and Gastrointestinal Cancers

Jan Kwasniewski developed his Optimal Diet something like 40 years ago and it has become extremely popular in Poland.

Kwasniewski recommended that adults should eat in the ratio

60 g protein – 180 g fat – 30 g carbohydrate

In terms of calories this is roughly 240 calories protein / 1640 calories fat / 120 calories carbohydrate on a 2000 calorie diet.

The Perfect Health Diet proportions are more like 300 calories protein / 1300 calories fat / 400 calories carbohydrate.  So the diets would be similar if about 300 calories, or 15% of energy, were moved from fat to carbohydrate in the form of glucose/starch (not fructose/sugar!).

Note that we recommend obtaining at least 600 calories per day from protein and carbs combined. This ensures adequate protein for manufacture of glucose and ketones in the liver. But the Optimal Diet prescribes only 360 calories total (less in women), suggesting that gluconeogenesis cannot, over any long-term period, fully make up for the dietary glucose deficiency.

In the book, we note that a healthy body typically utilizes and needs about 600 glucose calories per day. On the Bellevue All-Meat Trial in 1928 Vilhjalmur Stefansson ate 550 protein calories per day, which is probably a good estimate for the minimum intake needed to prevent lean tissue loss on a zero-carb diet.

With only 360 carb plus protein calories per day, the Optimal Diet forces ketosis if lean tissue is to be preserved. Since at most 200 to 300 calories per day of the glucose requirement can be displaced by ketones, the Optimal Diet is living right on the margin of glucose deficiency.

Gastrointestinal Cancers in Optimal Dieters

I learned over on Peter’s blog that Optimal Dieters have been dying of gastrointestinal cancers at a disturbing rate. Recently Adam Jany, president of the OSBO (the Polish Optimal Dieters’ association), died of stomach cancer at 64 after 17 years on the Optimal Diet. Earlier Karol Braniek, another leader of the OSBO, died at 68 from duodenal cancer.

A Polish former Optimal Dieter who has now switched to something closer to the Perfect Health Diet noted that gastrointestinal cancers seem to be common among Optimal Dieters:

The impression we get is that there’s rather high occurrence of gut cancer, including stomach, duodenum, colon … [source]

I want to talk about why I think that is, since the danger that the Optimal Dieters are discovering was one of the key factors leading us to formulate and publish the Perfect Health Diet.

Zero-Carb Diets Can Induce Mucus Deficiency

I ate a high-vegetable but extremely low-carb diet from December 2005 to January 2008. At the time I thought I was getting about 300 carb calories a day, but I now consider this to have been a zero-carb diet, since I don’t believe carb calories are available from most vegetables. Vegetable carbs are mostly consumed by gut bacteria, whose assistance we need to break down vegetable matter, or by intestinal cells which consume glucose during digestion.

Throughout my 2 years on this zero-carb diet, I had dry eyes and dry mouth. My eyes were bloodshot and irritated, and I had to give up wearing contact lenses. Through repeated experiments, I established that two factors contributed to the dry eyes – vitamin C deficiency and glucose deficiency. After I solved the vitamin C issue, I did perhaps 50 experiments over the following few years, increasing carbs which made the dry eyes go away and reducing them which made them immediately come back. This established unequivocally that it was a glucose deficiency alone that caused the dry eyes.

Rebecca reports similar symptoms in herself and her low carb friends.

This is also a well-known symptom during starvation. As a review cited by LynMarie Daye (and referenced by CarbSane in the comments) notes,

Since hepatic glycogen stores are depleted within 24 h of fasting, blood glucose concentrations are maintained thereafter entirely through gluconeogenesis. Gluconeogenesis is mainly dependent on protein breakdown (a small amount comes from the glycerol released during lipolysis) and it thus results in protein wasting. It is the effects of protein malnutrition that lead to the eventual lack of ability to cough properly and keep the airways clear, in turn leading to pneumonia and death during prolonged starvation; hypoglycaemia does not occur. [1]

Another common symptom of very low carb diets is constipation. This is often attributed to lack of fiber, but I am skeptical. I will get to the various possible causes of constipation in a future post, but for now I’ll just point out that a deficiency of gastrointestinal mucus would create a dry colon and cause constipation.

What connects a zero-carb diet to dry eyes, dry mouth, dry airways, and dry gastrointestinal tract?

Tears, saliva, and mucus of the sinuses, airways, and gastrointestinal tract are all comprised substantially of glycoproteins called mucins. Mucins are primarily composed of sugar; they typically have a number of large sugar chains bound to a protein backbone.

For instance, the main mucin of the gastrointestinal tract, MUC2, is composed of a dimerized protein – each protein weighing 600,000 Daltons individually, so 1.2 million Daltons for the pair – plus about 4 million Daltons of sugar, for a total mass of 5 million Daltons. In the mucus, these large molecules become cross-linked to form “enormous net-like covalent polymers.” (source)

If, for whatever reason, mucin production were halted for lack of glucose, we would have no tears, no saliva and no gastrointestinal or airway mucus.

Mucin Deficiency Causes Cancer

There is a strong association between mucus deficiency and gastrointestinal cancers.

H. pylori is the strongest known risk factor for stomach cancer. [2] H. pylori infection is found in about 80% of gastric cancers. [3] One reason H. pylori promotes stomach cancer so strongly may be that it diminishes mucus in the stomach, as this photo shows:

Top: Normal stomach mucosa. Bottom: Stomach mucosa in an H. pylori infected person.

Scientists have created mice who lack genes for the main digestive tract mucins. These give us direct evidence for the effects on cancer of mucin deficiency.

Experiments in Muc1 knockout mice and mice with Muc1 knockdown have shown that under Helicobacter infection, mice deficient in Muc1 develop far more cancer-promoting inflammation than normal mice. [4]

The main mucin of the intestine is Muc2. The group of Leonard Augenlicht of the Albert Einstein Cancer Center in New York has studied mice lacking Muc2. They develop colorectal cancer. [5]

Tracing backward one step toward the source of mucin deficiency, the sugars in mucin are built from smaller pieces called O-glycans. It has been shown that mice that are deficient in O-glycans are prone to colorectal cancer: “C3GnT-deficient mice displayed a discrete, colon-specific reduction in Muc2 protein and increased permeability of the intestinal barrier. Moreover, these mice were highly susceptible to experimental triggers of colitis and colorectal adenocarcinoma.” [6]

Nutrient Deficiencies Can Also Play a Role

Some micronutrients are required for mucin production – notably vitamin D. [7, 8] Poland is fairly far north, and many of the Optimal Dieters could have been low in vitamin D.

Other important micronutrients for cancer prevention are iodine and selenium. Poland in particular had the lowest iodine intake and among the highest stomach cancer death rates in Europe. After Poland in 1996 began a program of mandatory iodine prophylaxis, stomach cancer rates fell:

In Krakow the standardized incidence ratio of stomach cancer for men decreased from 19.1 per 100,000 to 15.7 per 100,000, and for women from 8.3 per 100,000 to 5.9 per 100,000 in the years 1992-2004. A significant decline of average rate of decrease was observed in men and women (2.3% and 4.0% per year respectively). [9]

So among the Polish Optimal Dieters, the elevated gastrointestinal cancer risk caused by mucin deficiency may have been aggravated by iodine and sunlight deficiencies.


A healthy diet should be robust to faults. The Optimal Diet is not robust to glucose deficiency.

There’s good reason to suspect that at least some of the Optimal Dieters developed mucin deficiencies as a result of the body’s effort to conserve glucose and protein. This would have substantially elevated risk of gastrointestinal cancers. Thus, it’s not a great surprise that many Optimal Dieters have been coming down with GI cancers after 15-20 years on the diet.

We recommend a carb plus protein intake of at least 600 calories per day to avoid possible glucose deficiency. It’s plausible that a zero-carb diet that included at least 600 calories per day protein for gluconeogenesis would not elevate gastrointestinal cancer risks as much as the Optimal Diet. But why be the guinea pig who tests this idea?  Your body needs some glucose, and it’s surely less stressful on the body to supply some glucose, rather than forcing the body to manufacture glucose from protein.

Fasting and low-carb ketogenic diets are therapeutic for various conditions. But anyone on a fast or ketogenic diet should carefully monitor eyes and mouth for signs of decreased saliva or tear production. If there is a sign of dry eyes or dry mouth, the fast should be interrupted to eat some glucose/starch. Rice is a good source. The concern is not only cancer in 15 years; a healthy mucosal barrier is also essential to protect the gut and airways against pathogens.

Related Posts

Other posts in this series:

  1. Dangers of Zero-Carb Diets, I: Can There Be a Carbohydrate Deficiency? Nov 10, 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] Sonksen P, Sonksen J. Insulin: understanding its action in health and disease. Br J Anaesth. 2000 Jul;85(1):69-79. http://pmid.us/10927996.

[2] Peek RM Jr, Crabtree JE. Helicobacter infection and gastric neoplasia. J Pathol. 2006 Jan;208(2):233-48. http://pmid.us/16362989.

[3] Bornschein J et al. H. pylori Infection Is a Key Risk Factor for Proximal Gastric Cancer. Dig Dis Sci. 2010 Jul 29. [Epub ahead of print] http://pmid.us/20668939.

[4] Guang W et al. Muc1 cell surface mucin attenuates epithelial inflammation in response to a common mucosal pathogen. J Biol Chem. 2010 Jul 2;285(27):20547-57.  http://pmid.us/20430889.

[5] Velcich A et al. Colorectal cancer in mice genetically deficient in the mucin Muc2. Science. 2002 Mar 1;295(5560):1726-9. http://pmid.us/11872843.

 [6] An G et al. Increased susceptibility to colitis and colorectal tumors in mice lacking core 3-derived O-glycans. J Exp Med. 2007 Jun 11;204(6):1417-29.  http://pmid.us/17517967.

 [7] Paz HB et al. The role of calcium in mucin packaging within goblet cells. Exp Eye Res. 2003 Jul;77(1):69-75. http://pmid.us/12823989.

[8] Schmidt DR, Mangelsdorf DJ. Nuclear receptors of the enteric tract: guarding the frontier.  Nutr Rev. 2008 Oct;66(10 Suppl 2):S88-97. http://pmid.us/18844851.

[9] Go?kowski F et al. Iodine prophylaxis–the protective factor against stomach cancer in iodine deficient areas. Eur J Nutr. 2007 Aug;46(5):251-6. http://pmid.us/17497074.

Leave a comment ?


  1. I would be extremely interested to see Paul’s notes / documentation from the two year period where he was experimenting with carbs. I’m just curious on a day to day basis how he felt, it would be cool to see the progression of improvement with increased carbs. Paul, I think you’re a brilliant, genius mastermind, and I love your enthusiasm and your humility. I have the utmost respect for you and Shou-Ching, and appreciate extremely the work that you do.

  2. Side Effects of Low Carb Diets: TSH, LDL, Dry Eyes | Harpoon - pingback on August 25, 2014 at 1:43 am
  3. This is the first article I have ever read that makes sense as to why my mom died from stomach cancer…. Wow.

  4. Thank you for highlighting he role mucins play in protecting epithelia. I spent a lifetime researching a particular corneal disease and it was the research of these glycosylated, hydrophilic glycoproteins that steered me into investigating the gut lining and its connection to inflammatory conditions. I met researchers from Queensland Australia quite a few years back at a conference whose research focus was incorporating these mucin molecules onto contact lens surface. Of interest is the fact that contact lens wearers have a higher incident of the corneal condition. I don’t think its coming from the contact lens wearing per se but a result of a deficiency in these mucins on the corneal surface that makes the cornea vulnerable to infection and inflammatory events. A give away sign is dry cough, constant throat clearing sounds, vaginal dryness etc. Starvation diet are problematic. When you think of how much of the cell is made up of these glycoproteins – sugars attached to proteins, makes you skeptical about following a low sugar/carb diet. For those of us restricted to wearing hard contact (RGP) lenses, we are quickly alerted to mucin deficiency and the need to for dietary changes. Others will need to look for other signs. Vaginal dryness in menopausal women also coincides with dry eye conditions such as Sjorgrens or ‘Dry Body’ syndrome.

  5. Anonymous - pingback on August 31, 2014 at 8:21 am
  6. Hi,

    I came across your website while researching various stuff relating to Auto immune diseases.

    I recently had a EDG and colonoscopy and one of the diagnoses (apart from Ulcerative Colitis) is that I had intestinal metaplasia.

    I have been on a ketogenic diet since May 2014, so not a very long time, but is there any way that could have contributed to the metaplasia.

    Also, I have had cold/sniffles at least 4 days every week for as long as I can remember. In the ketogenic diet, I have gone for weeks without a sneeze. I was thinking this is a good thing, but could this be a symptom of drying out ?

    Any pointers you can give me would help. Thanks..

  7. Have you been tested for H. Pylori infection? Hydrogen breath test? Have you been taking painkiller medication? How extensive is the intestinal metaplasia and how long have you been suffering ulcerative colitis?

  8. Hi Ella,

    I have bee tested for H pylori and it was negative. I admit I have not heard of hydrogen breath test, I will ask my GI about it.

    I was just diagnosed with UC specifically ulcerative proctitis shout 2 weeks back, but I am certain I have has it for at least 3 years.

    My GI mentioned that I have metaplasia sons acute chronic gastritis. I am not sure how extensive that is. I will ask him again.

    Thanks for your response.

  9. Kiran, email me at rella@westnet.com.au for more detailed info.

  10. I was just released from the hospital on 3-15-15 for this very thing! I went on a zero carb keto diet for 8 weeks, lost 28 lbs, was feeling great, then BAM! Went into the hospital for severe bloody stools, terrible stomach cramps etc. After all the tests Dr. said I had ulcerative colitis or Crohn’s. After being in the hospital for a week, eating carbs and sugar again, my body started to heal itself. The Dr.’s couldn’t believe it. I told them about the Keto diet and the decreased mucus production and they were stunned. So many doctors don’t know about this. Now that carbs are back in my system I am healing up. I was in the hospital for 9 days. Stay away from KETO diets!!!! It’s not worth the risk.

  11. Iodine kills the h.pylori and increases fluids in the body for lubrication.
    Dry mouth, eyes, lack of sweat and low stomach acid are symptoms of iodine deficiency.

  12. Paul you fail at a good explanation of your mucus reason for uping carbs
    Tao has a 2500 year tradition of no grain diet

    Ask your wife to read in Chinese.

    Why raise blood sugar and Insulin .
    Seriously blood sugars in the 90’s? Not good IMO

  13. After being on a zero carb diet for nearly two years, I fear I have trashed my health so much more than it was before I did the low carb diet. I’ve been desperately trying to add in some carbs following the PHD, but I am really struggling. I do believe I have SIBO, so I don’t know if that’s the problem, but even with adding in just a tablespoon of white jasmine rice daily I am getting frequent, excessive urination with incomplete emptying of my bladder. I also find that my urine has a “rice smell” to it. What could be causing this?!

    • You have diabetes.

      Frequent urination, that especially smells like your only sugar source is most definitely diabetes.

      Increasing b-vitamins in conjunction with sugars is the best for absorption.

      Nutritional yeast is the best source of all b-vitamins, combine this with your carb source and analysis results.

      • Whoa, I have sibo and interstitial cystitis (which also makes urine smell “off”) but no diabetes. I tried PHD for sibo, but now doing FTD. After healing my gut, I can now after almost 2 years low carb, eat a little jasmine rice if soaked 10 hrs. Ultimately I want to go transition back to PHD, but wondering how to avoid feeding sibo. And don’t tell me it’s curable 😢

  14. Hi Paul,

    I’m a huge fan. I have a 3-year old daughter who does not want any of the starchy carbohydrates I make her: potatoes, rice, tapioca flour cheese buns, etc. Her only carb intake is a huge amount of fruit and some dark chocolate chips. She even turns her nose up at the cookies and muffins I make her with tapioca flour in favour of fruit. She eats plenty of meat and fat as well. Is it possible to be deficient in glucose if eating lots of carbs, but in the form of fruit? For example, her carb intake for one day might be: 3 bananas, 1 apple, a handful of raisins, and a mango. She is 32lbs, so a bit slim.

    Thanks in advance for any insight you could provide!

    • Hi Jen,

      That does sound like a low carbohydrate intake for a child, but I guess I wouldn’t worry about it. I’d just continue making starches available and eating them yourself, and at some point her body will tell her that she needs them and that they taste good. Maybe you can mix potatoes into complex meals, e.g. stews or curries.

  15. What’s Up With White Rice? | Phoenix Helix - pingback on July 25, 2015 at 11:22 am
  16. How would one go about increasing carbs when. SIBO (per breath test and long-standing symptoms) causes immediate abdominal distention and fluid retention when eating starch, sugar or fiber?

    I have been low-carb for a long time due to the above reason ( as well as having been convinced by Mark Sisson et al that it was a healthy choice). As a living example of the article I now have a very disturbed thyroid profile, dry eyes ( currently nursing an eye infection) fatigue etc.

    I wholeheartedly believe that eating a sufficient amount of starch is optimal, but how do I, and the large number of other individuals that suffer from SIBO, go about doing this?

    Thanks a million for any advice!

  17. Addendum: to clarify, I have been on multiple courses of antibiotics, used herbal antimicrobials for years etc. The only thing I’ve yet to try but am considering next is LDN to increase intestinal motility. SCD diets, the aforementioned carb retraction etc are helpful only in terms of temporary symptom alleviation, but as soon as I introduce carbs/ fiber, I’m back at square one.


  18. Wow, this is really interesting! I had a stomach tumour removed about a year ago. I wasn’t low carb so I don’t think my cancer was caused because of this but this is important to me for my diet for the future.

    I’m not sure what caused my cancer. It was a GIST.

    Thoughts on the pale diet anyone? Would this diet cause more cancers???

    • Hi Vonny,

      I would say that low-carb versions of Paleo would increase risk of gastrointestinal cancers, but normal-carb versions like the Perfect Health Diet would reduce the risk. However, other factors, like iodine intake, intermittent fasting, and circadian rhythm entrainment, are probably at least as important.

      Best, Paul

  19. Mucus and Low Carb | Normal Carb - pingback on August 20, 2015 at 7:15 pm
  20. Nerds and they’re nonsense.

    Sorry, but I disagree with all your theories.
    You cannot track or take into consideration all impacting differences in each others lives and bodies.

    An ENTP, any ENTP can tell you, you can take any bit of information and make it true, even finding “scientific data” about it.

    Keto helped my dry eyes for the “record”

  21. What a crock!!

  22. Hi

    I haven’t heard anyone mention Vitamin A. Vit A is one of the most important nutrients to consume if you want to produce an abundance of mucous through the GI track. Especially the stomach lining and intestinal walls and colon. Liver in animals is by far the highest source, know other foods come close and the Vit A from animal based foods is highly absorbed, plant sourced Vit A is very hard for humans to absorb like carrots for instance.

    So I believe where a lot of zero carb diets break down is that animal organs are not consumed readily enough, and not just for the Vit A. Organs meats far exceed plant food for overall nutrient contents and absorbability in general.

    I myself eat a zero carb diet and I have strictly for the past 10 years(zero vegetation). I consume liver atleast 3-4 times a week, and other animal organs generally on a daily basis. I suffered with celiac disease for most of my life with severe diagnosed dry eye syndrome, and other autoimmune conditions. But fortunately for me I don’t suffer from any of these conditions anymore. Dry eye is a non issue.

    Also I cycle about 300klm a week and race A grade. And coach Tennis on a full time basis, all without any carbohydrates. I never feel hungry or low on energy, like I did when eating a high fibre low fat diet. Interestingly I don’t suffer from constipation at all, but I did severely when I ate high fibre.

    Also you get all the Vit C you need from animal organs especially from liver. I have no sign of scurvy at all.

    Lastly google research a bit into Vit K2, Vit A, Vit D and calcium and how they all connect/interact with each other.

    My believe is this is where a lot of zero carb diets break down. I know it did for me in the early experimental stages. But not anymore.

    I hope some of this helps.

    • smokey quartz

      Hi Jeff; hopefully you are getting notifications from this thread still. This is really interesting to me. I would like to do a very low or zero carb diet eventually for neurological health (I have epilepsy). I’m afraid of taking MCT oil to create ketones, as supplements sometimes cause me to feel lightheaded. From reading the Perfect Health Diet and also some WAPF articles written by Chris Masterjohn, I learned that vitamins A and D have to be in a certain ratio in the diet. Vitamin D is hard to come by but it prevents toxicity symptoms from vitamin A. How do you balance these two nutrients in your diet?

      Also, I’ve read that on a zero carb diet it’s important to have a lot of fat. I did try that, but it gives me heart palpitations (feels like skipped beats or a flutter) afterwards. Do you ever feel this? If so, what did you do to fix it? Is it the organ meats that help? Do you eat the liver raw or cooked? I try to eat liver but can only manage a couple forkfuls and never the whole thing (even with onions).

      I truly appreciate any feedback from your experience. Thank you so much.

      • Hi Smokey,I guess you’ve researched zero carb diets for epilepsy, I have to and the results seem very positive for this kind of diet approach,I definitely think it could help your epilepsy,I don’t see any harm in at least trying.

        I have used coconut oil without any problems but I personally prefer to use lard or butter. And yes I consume large amounts of these fats and any animal based fats in general.

        As I have stated liver is a meal I eat 3-4 times a week(200g per serving)and have done so for a lot of years religiously.I once ate liver every day for over a month without any signs of vit A toxicity or any other toxicities for that matter. Interesting experiment, made me realise not to believe everything you read on the net. At that dose according to quite a few medical experts I should of definitely experienced some kind of reaction, but for me the complete opposite, only good health and energy. IMO I think vit A toxicity occurs from synthetic vit A not naturally sourced vit A. Also in it’s natural state I think all the other nutrients in the food you consume help to keep toxicities at bay, again this is just my opinion, know proof. By the way I eat my liver raw occasionally but mostly lightly cooked,fortunately I like the taste of liver so have know problems consuming large amounts. Try cooking your liver as a meat paddy(mixed together), say 2 parts mince one part liver add in some herbs for taste, my sister makes them that way and they taste really nice, even the kids eat them!

        Eating zero carbs without consuming organ meets for me was okay I definitely improved but it was only when I started consuming lots of organ meats all long standing issues cleared up fairly quickly for me.

        I was suffering some strange heart issues like you mentioned( when I was eating mostly vegetarian food years ago) and even a bit worst which my doctor thought I should have checked out, but the change to Zero carb especially with organ meats completely cleared that up.

        Again my diet is very high in fat at least 80/20 (fat/protein)I buy all fatty cuts of meat, cook in glass pie plates and pour the left over fat back on top of the meal and consume it all. It takes a while for your body to handle consuming large quantities of fat but once you do energy levels increase significantly.It did for me!

        Again IMO you don’t need carbs for energy fat is the perfect fuel.

        Hope this helps you.

        • Balancing your electrolytes can help with heart palps. Low carb diets are diuretic and sodium needs to be replaced. So does potassium and magnesium. My palps stopped once I got the right balance of salt, potassium and magnesium.

        • Brian Hardaway


          The other nutrients in liver do not prevent vitamin A toxicity as evidenced by the arctic explorers who died after consuming polar beat liver from vitamin A toxicity.

          • Polar bear liver’s vitamin A content is hundredfold of chicken liver’s. You would need to eat 10kg chicken liver to get the same amount of vitamin A as 100g polar bear liver.

          • Brian Hardaway


            That is beside the point. Polar Bear liver is a natural source and clearly produces toxicity. Also, if you read my post below, the threshold for toxicity differs between people. Those who produce lower levels of retinol binding protein are at a greater risk of toxicity at lower doses. When I ate a zero carb diet and got about 5000 IU per day from ghee/butter, I experienced toxicity symptoms after a period of time. They were much less severe than the last time when I was taking 100,000 IU per day. The supplement I was taking was retinyl palmitate. Retinyl palmitate is the primary storage form of vitamin A in all animals. Whether it is from a supplement or food, it is equally toxic, especially for those who have lower levels of retinol binding protein.

      • Magnesium can prevent seizures in many cases of epilepsy. It may be worth reading about.

    • Brian Hardaway

      Be very careful with vitamin A. Excess vitamin A can cause severe gastrointestinal damage and brain damage. I am a biochemical graduate student at the University of Michigan and am working on a hypothesis involving vitamin A and Alzheimer’s. Different people naturally produce different amounts of retinol binding protein. Vitamin A bound to this protein is harmless. But, free vitamin A is toxic and can cause large amounts of oxidative stress that kills neurons. Those who naturally produce lower levels of retinol binding protein have a lower threshold for toxicity. A couple of studies I looked at show that Alzheimer’s patients have lower levels of retinol binding protein than controls.

      Also, excess vitamin A actually inhibits mucous production and can cause severe damage to the gastric mucosa.

      I experienced all of this first hand. Severe gastrointestinal damage and memory loss/confusion after supplementing with 100,000 IU per day for 5 weeks (along with ample vitamin D…15,000 IU per day). The studies I had read up to that point indicated that people routinely tolerate 300,000 to 500,000 IU daily with few issues. Clearly, the sample size of those studies was too small.

  23. Peter’s blog said one dieter got stomach cancer, and it could have been due to the high incidence of stomach cancer rates in the country she was living in. Why cite the post if you are going to be misleading about what it claims?

  24. Why would one get gastro cancers from low carb?
    As long as eating enough veg and getting enough fibre, there is no problem.

  25. There are a lot of benefits to a low carb, high saturated fat diet, but I’ve definitely noticed some weird eye issues and MUCH more sensitive stomach whenever I’ve been around 30g of carbs a day for a few days. Also get pretty intense carb cravings around the same time.

  26. Have you thought about the high stomach cancer rates in Poland being related to the high pork consumption of optimal dieters?

  27. South Korea has the highest rate of stomach cancer of any country I think, and they eat a lot of carbs.

    I’ve researched the pork/poland thing, and Poland has a disproportionately high amount of their meat consumption as pork, moreso than any other country I think.


  28. Zero Carb Diet - pingback on March 30, 2016 at 6:42 am
  29. Can Ingesting Collagen Improve Your Digestive Health? - pingback on May 31, 2016 at 10:42 am
  30. Excellent article Paul. Thank you.

    Could you please direct me to where I can find an overview of how you overcame Candida? I searched your book on Amazon but didn’t come up with any references to Candida.

    I am dealing with Candida and SIBO and believe I need more HCL but become very acidic when I take it. Taking alkalinizers seems to worsen the Candida and SIBO. Also, protein enzymes cause incredible intestinal pain. Carbs also worsen things. For sometime now I’ve realized that I’m dealing with a low mucin issue but can’t seem to find a way out of this maze.

    Thanks much in advance for your response.

  31. One more thing…L-Glutamine causes major headaches. Have you discovered a way around this. I would love to try bone broth.

  32. LAM – I’m knew here – transitioning at my own pace off 25-30 carbs. I’m at 50 and holding for now. I’ve added just steamed sweet potato and a small amount of beets/carrots. My first week I did 80 carbs and gained two pounds – scared myself LOL! Lost it pretty quick those reducing my carbs to 50. I don’t eat white rice – period. I don’t eat fruit except avos and red bells peppers. This is not a free for all for me. I know I need to go slow and add carbs one at a time…so far Japanese sweet potato – one a day mixed up in my daily bowl of 6 oz protein (including 3 boiled eggs), 1/2 cup spinach/brocoli cooked, 12 baby carrots and one small beet – steamed or and 1/3 cup orange winter squash…2 tabs my homemade mayo – chopped up and mixed in my daily bowl and wrapped in nori sheets – I eat ever 2.5 or 3 hours stop at 5 start again at 7am…so far so great! I’ve been a paleo/primal girl for 8 years – nixing fruit and dairy works well for me…just my two cents…good luck!

  33. LAM – oops forgot – I also do a cup of beef or chicken bone broth daily…add a bit of spinach and a raw egg to boiling broth – instant straccatella soup…Real Salt to taste…perfect for my first meal…:)

  34. Paul,

    This is the first time I have come across a blogpost that connects a low carb diet to gut cancers.

    Since Poland is north, they may have a vitamin D deficiency which compounded the issue with the lack of musins.

    While you were on a low carb diet, and having symptoms of dry eyes and mouth, did you get enough vitamin D?

    I am on a low carb diet and have not experienced any of the symptoms. I do take 5000IU of vitamin D each day.

  35. Now I am confused, seriously. In my case, I seem to be producing too much mucus, saliva and floods of tears. I recently embarked upon a Keto diet to see if the excess mucus would abate. I take my vitamins regularly, and I also use a carefully selected set of herbs for cyclical use. Nothing seems to be helping my mucus production. Then I came across this blog post. My diet consisted mainly of carbs, which is why I opted to switch to a Keto diet. I don’t necessarily want to give up on carbs. If your arguments are valid, how can my situation be helped by a primarily carbohydrate diet? Wouldn’t a Keto diet rather mitigate my problems?

    • Hi Memma, have you consulted a doctor? I am not familiar with conditions that cause excess mucus, saliva, and tears. If carbs are an issue I doubt it would be necessary to go all the way to a keto diet, you could just go to a lower carb diet.

      Best, Paul

  36. Keto Problems: Too Little Carbs? – Keto Sister - pingback on March 11, 2017 at 7:50 am
  37. I think if people who use low carb diets supplement with electrolytes and fluids like they should be, then becoming dehydrated should not be a problem. Low carb diets are diuretic and salt needs to be replaced often. So does magnesium and potassium. Plus eat food that with probiotic foods to help control H.Pylori.
    My extreme dry eye was cured by going to a keto low carb diet. It is amazing!! I actually produce tears now! And have salt in my tears! The healthy fats and sodium helped a lot. My eye lids no longer stick to my eye balls at night and cause pain. I think any diet could create a deficiency situation so what ever diet you choose you need to do your homework and do it correctly. Supplement where needed etc. I was not healthy on a conventional diet where I ate lots of carbs. I had all kinds of deficiencies. Now I am more aware of these and supplement where I need too.

  38. Don’t forget that Polish people drink a lot of alcohol and eat a lot of sliced meats, sausages etc.

  39. Low Carb Diet: Can You Go Too Low? | Low Carb Diet - pingback on September 26, 2017 at 8:05 am
  40. If I eat carbs my blood sugar spikes but I never test high for insulin levels or c-peptide for the past ten years – always a little below normal to low normal. Fasting blood sugar in the 90’s and the spikes, such as if I eat rice, can be as high as 160. And I’m not talking about eating a big plateful. Also seem to have SIBO and other digestive issues. Low carb keeps my A1C at around 5.5 and I also lose no weight on 1500 calories a day unless it’s low enough in carbs to be ketogenic. I am at the top of “normal” BMI but I have a small frame for my height and would be better if I lost another 10-15 pounds. So – then I read this and wondering what on earth one is supposed to do if this is true! Diabetes drugs are garbage and full of side effects and when I was eating an amount of carbs that were still a bit lower than many people I know I ended up with an A1C of 6. Also I have never had high triglycerides, have a very high HDL, normal LDL and normal blood pressure and relatively small waist so no one can tell me why I have the blood sugar issues to begin with. It’s very hard to deal with all the conflicting suggestions and information from various sources!

  41. Paul, this article is outstanding! Thank you for sharing your knowledge! I’m scared. I’ve been in deep ketosis for 1 1/2 years, with virtually no starch in my diet. For the last 6 months, I’ve been experiencing terrible symptoms of: dry mouth, fissured/cracked tongue, dry eyes, dry throat, dry airways. I fear I may have triggered Sjogren’s Syndrome in my body. All blood work came back negative but I know that one can still have Sjogrens without the antibodies. Two days ago, I started back eating rice and starches. I still have all these symptoms. Please help! Do I need to be more patient?? Thank you so much.

    • Hi Grant,

      Eat more starch and fruit, and take vitamin C to close to bowel tolerance for a few days and then 2 g/day until you feel better.

      Best, Paul

      • Thank you so much for getting back to me, Paul! Much appreciated!

        • You’re welcome. Also take other PHD supplements including a B50 complex once a week. You might get a little extra vitamin A for a bit too.

          • Will do, Paul! Thank you! Just curious… What’s the function of the Vitamin C for symptoms like I have? What’s the mechanism of action? Thanks again!

        • Hello Grant,

          i have the same yhing 🙁
          Did you imporve ? And how long it took ?

          Thanks !

  42. Hi Paul,

    Might there be a way on the website to access your content/comments from the Q&A sections (e.g. a profile page w/ thread content link, etc.)? Love keeping up with your observations/gems that stem beyond the book.

    Thanks for your contributions. Truly a difference maker in many lives. Billy

  43. Cancer requires sugar.

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