Short-Term Effects of Adding Carbs to Very Low-Carb Diets

In my last post, I noted that

So far, all the negative experiences [from adoption of our diet] I am aware of have come from low-carb dieters who had difficulty after adding carbs and/or cutting protein….

It’s interesting that the same dietary change – adding “safe starches” to a low-carb Paleo diet – made some people feel better and others worse.

In thinking about why adding starches can cause short-term trouble for some people, my first thought was a fascinating post from two years ago by Peter Dobromylskyj of Hyperlipid. Peter noted:

Bacterial endotoxin is a breakdown product of the cell wall of gram negative bacteria. It’s a lipopolysaccharide and even quite small amounts of it are extremely unpleasant….

Now the scary thing is that eating a high fat meal, probably based on any fat which generates chylomicrons, markedly increases your uptake of endotoxin from your gut, which is obviously full of gram negative bacteria. Eating short chain fatty acids or carbohydrate [1] does not have this effect.

Endotoxins are fat-soluble, and so fat carries them into the body. The paper Peter cited actually found an increase in blood endotoxin levels after people were fed a high-fat meal:

In humans, no significant relation was observed between cardiovascular disease risk factors, carbohydrate and protein intakes, and plasma LPS concentration. Conversely, positive correlations were observed with fat and energy intakes. [1]

The same effect was found in mice:

Compared with the control mice, mice fed a high-energy diet showed an increase in plasma LPS. However, in mice fed a high-carbohydrate diet, the increase in plasma LPS was blunted compared with mice fed a high-fat diet.

The conclusion:

Experimental data suggest that fat was more efficient in transporting bacterial LPS from the gut lumen into the bloodstream. [1]

Does this mean that one should avoid dietary fat?  No, because it turns out the body regulates the amount of endotoxin entering the body. So a high-fat diet causes the immune system to exert greater control over gut bacteria. Peter writes:

Then came a fascinating random paper [2] through my wife’s journal club meetings … It’s about superinfection with resistant bacteria when broad spectrum antibiotics are used. This is a routine problem for anyone in medicine, especially patients. The concept is very simple, you kill off the susceptible commensal bacteria in the gut and resistant pathogens have no competition, so they have a field day and superinfection causes severe problems for the unlucky patient.

Simple, straightforward and wrong.

It turns out that the immune system, that is the innate immune system (of course), continuously monitors the contents of the gut by looking at endotoxin production. Lots of bacteria mean lots of endotoxin and an active, on-guard innate immune system. Kill off 99% of your gut bacteria and exdotoxin production drops. The innate immune system goes on vacation and clostridium difficile gets in and wipes out your granny.

Simple administration of oral endotoxin to the experimental mice stopped this effect completely.

Apparently, the human body evolved to favor having a certain population of commensal gut flora. When the population is too low, immune defenses are lowered to allow gut bacteria to multiply. When the population is too high, antimicrobial peptides are released into the gut to control pathogen numbers.

Thus, during gut infections adding probiotic bacteria may help defeat pathogenic infections by causing the body to increase its immune defenses. The body is actually trying to control the numbers of probiotic bacteria, but in doing so it makes compounds that kill pathogens.

Removal of tiny numbers of probiotic bacteria can lead to a huge multiplication of pathogens:

Administration of the broad-spectrum antibiotic combination metronidazole, neomycin and vancomycin (MNV), to which vancomycin-resistant Enterococcus (VRE) is resistant, markedly increases colonization of the small intestine, caecum and colon with VRE…. It remains unclear, however, why elimination of the relatively sparse microbial flora of the small intestine increases the number of VRE by over 100–1,000-fold. [2]

It’s possible that this effect may be able to work in reverse – that addition of the small number of bacteria in a probiotic capsule can diminish the much larger population of an acute infection by 100-fold. I’ve noticed that swallowing probiotic capsules can be extremely effective against food poisoning. If you ever get diarrhea from a bad meal, take handfuls of probiotics every few minutes. You’ll be cured remarkably quickly.

The Gut of a Zero-Carb Dieter

On a zero-carb diet – especially an entirely plant-free diet like the one Charles Washington eats – lack of food will cause the population of gut bacteria to dwindle.

As in a gut depopulated of bacteria by antibiotics, this diet will cause the gut to let down its immune defenses. The body will reduce its production of antimicrobial peptides in order to help gut bacteria survive.

Perversely, this may make any pathogens that enter the body with food more likely to enter the body. It also may allow pathogens to gain a foothold in the gut. Thus, heightened infectious disease risk could be another long-term danger of zero-carb diets.

What Happens When A Zero-Carb Dieter Reintroduces Starches?

When a zero-carb dieter starts eating plant foods, suddenly gut bacteria have a lot of food, and can multiply many-fold. Bacteria can double their numbers in 20 minutes, and yeast in a few hours. That means that bacterial populations can increase 8-fold in an hour, 4000-fold in 4 hours, and ten million fold in 8 hours. Yeast can increase 4000-fold in 24 hours.

So it doesn’t take long – the very first day – before gut bacteria have multiplied by huge proportions. In the course of their fermentation, they’ll release a lot of gas, causing some bowel distress.

And along with greater numbers comes greater endotoxin release. Any dietary fats carry these endotoxins into the body. This rise in endotoxin load triggers an immune response that includes release of antimicrobial peptides, killing gut bacteria and releasing more endotoxins.

This rise in endotoxin levels and the resulting immune response may resemble a brief illness. Some known effects of a sudden rise in systemic lipopolysaccharide levels:

  • Depression [3] and depressive-like behavior [4].
  • Impaired athleticism [5]. 
  • Reduced appetite [6, 7].
  • Fever, vasoconstriction and endothelial dysfunction. [8]

Of course these effects would be only temporary. In a matter of days to a week, the immune system should re-establish an equilibrium with the gut flora and the new diet. Gas and bloating in the gut should be reduced (unless pathogens have been able to establish an enduring infection first). Endotoxin levels in the body should return to the evolutionary optimum. Higher production of antimicrobial peptides will maintain a limited gut bacterial population, even though carb intake has increased.

My Experience

My own experience is consistent with some of these expectations. When I went from zero-carb to including carbs – in my case, the change was adding fruit only, starches didn’t start for another year – my abdomen became bloated and I had gas. It was remarkable:  the very first day I ate fruit, my belly bloated up. It seemed to leave me with a lasting infection, because both the bloating and various digestive problems lasted several years. Probably the scurvy that I also had at that time was a big contributor; until I fixed the scurvy I also had gallbladder problems, and developed diverticulitis during this period, diagnosed by a barium enema.

I believe the main factor in the bloating was a colonic yeast/fungal infection that may or may not be completely gone today (it is certainly much diminished). The bloating was increased whenever I developed fungal skin infections. I suspect the yeast took over my colon while my immune defenses were depressed on the zero-carb diet and vitamin C deficiency, and multiplied immensely as soon as they had access to plant foods.


This hypothesis matches some but not all of the first-couple-of-days symptoms experienced by Don Matesz and his commenter SamAbroad when they cut protein and increased starches. SamAbroad became “hungry and cranky”; Don noted “decline in mood and … increase in hunger and intestinal gas and a disruption of bowel function.” In short:

  • Gas, bloating, intestinal distress.
  • Cranky mood.
  • Hunger.

The first two are consistent with a rise in endotoxin levels. The last isn’t.

However, I can imagine a few reasons why a shift from meat to starches may have made them hungry:

  • Protein is notably satiating, one reason why high-protein diets are often effective for weight loss. Mixed carb and fat, on the other hand, makes a good dessert. As we have all witnessed, many people say they are stuffed after dinner but get hungry again when they see desserts.
  • Or maybe the calories lost from the reduction in meat were not fully replaced. Plant foods have far fewer calories per pound than meat, and many people overestimate how many calories are found in plant foods. In cutting meat from

The body should adjust appetite to the diet, but this may not happen in the first few days. In short-term (3-day) trials of food mix alteration, people who increased carbs ate more food than people who increased protein. [9]

I don’t know if these explanations are correct in the specific cases of Don and SamAbroad. (Indeed, I was very surprised Don had any trouble at all, since he already eats our safe starches and I am pretty sure he also eats within our recommended optimal range of macronutrients — hat tip to commenter Beth Mazur of for a link to one of Don’s meal analyses in which he ate our recommended calorie ratio.) However, I think many people who have been on zero-carb diets can expect short-term gut distress when they first restore carbs to the diet.

In people with healthy gut flora, this should disappear in a few days. In others, like me, who have pathogenic gut populations, a gut infection may become entrenched and take longer to get rid of. Still, overall I think the inclusion of dietary carbs, and the resulting enhancement of intestinal barrier immunity, is likely to lead to long-term improvement in the body’s protection against infectious diseases that enter through the gut.


[1] Amar J et al. Energy intake is associated with endotoxemia in apparently healthy men. Am J Clin Nutr. 2008 May;87(5):1219-23.

[2] Brandl K et al. Vancomycin-resistant enterococci exploit antibiotic-induced innate immune deficits. Nature. 2008 Oct 9;455(7214):804-7.

[3] Weidenfeld J, Yirmiya R. Effects of bacterial endotoxin on the glucocorticoid feedback regulation of adrenocortical response to stress. Neuroimmunomodulation. 1996 Nov-Dec;3(6):352-7.

[4] Fu X et al. Central administration of lipopolysaccharide induces depressive-like behavior in vivo and activates brain indoleamine 2,3 dioxygenase in murine organotypic hippocampal slice cultures. J Neuroinflammation. 2010 Aug 2;7:43.

[5] Sparkman NL et al. Effects of intraperitoneal lipopolysaccharide on Morris maze performance in year-old and 2-month-old female C57BL/6J mice. Behav Brain Res. 2005 Apr 15;159(1):145-51.

[6] Stengel A et al. Lipopolysaccharide differentially decreases plasma acyl and desacyl ghrelin levels in rats: potential role of the circulating ghrelin-acylating enzyme GOAT. Peptides. 2010 Sep;31(9):1689-96.

[7] Rorato R et al. Prostaglandin mediates endotoxaemia-induced hypophagia by activation of pro-opiomelanocortin and corticotrophin-releasing factor neurons in rats. Exp Physiol. 2009 Mar;94(3):371-9.

[8] Feng SY et al. Acute and chronic effects of endotoxin on cerebral circulation in lambs. Am J Physiol Regul Integr Comp Physiol. 2010 Mar;298(3):R760-6.

[9] Coelho JS et al. Selective carbohydrate or protein restriction: effects on subsequent food intake and cravings. Appetite. 2006 Nov;47(3):352-60.

Leave a comment ?


  1. Hi Paul,

    You mention that you had gallbladder problems until you fixed your scurvy. I am experiencing some gallbladder issues and am hoping you might be able to help me. I’d really like to be able to save my gallbladder if I could.

    A little history: I have had Lyme Disease for the last 6 years and have been treating it with antibiotics for the past 2 years – recently did 2 months of IV ceftriaxone, but had to stop because I started having severe gallbladder attacks.

    Ceftriaxone is known to create it’s own type of gallstones and sludge, and people with gallbladder issues often end up having to have them removed after doing IV Ceftriaxone. I didn’t think I had any gallbladder issues, but it turns out that I did, but it wasn’t diagnosed (over the last 5 years I have woken up many many nights with intermittent intense pain on my left backside and lying on my right side would make it worse, but didn’t know what it was).

    I’ve been off ceftriaxone for 6 weeks now, eliminated fat from my diet for a week or two, but had another attack after I added a bit back in. An ultrasound 4 weeks ago showed 5mm stones. I’ve been eating basically zero fat for the last few weeks, but am still getting a mild, gripping pain in my gallbladder sometimes after meals. The smallest amount of fat (3gm) or sugar will set it off.

    I’m taking Ursodial once a day to help dissolve the cholesterol stones. I’ve also been drinking the juice of 1 or 2 lemon per day, as I saw you’d recommended on another post. I recently did a 3 day juice fast during which my gallbladder felt much better but returned to it’s uncomfortable state immediately afterwards.

    I’ve been thinking of trying Vitamin C injections or Milk Thistle or Swedish Bitters but I am afraid of the possible consequences – my doctor and naturopath warned me that anything that encourages flushing of the gallbladder may result in a rupture.

    Basically nothing seems to be helping very much, and I don’t know what to do. I don’t know what to eat, and I’m scheduled to see a gallbladder surgeon soon, who I’m sure is going to recommend removing it.

    If you have any thoughts on how I might go about healing my gallbladder, Paul, I would really appreciate hearing them.

    Thank you for your time Paul. Love your blog!

  2. Hi DeNon,

    Wow, that’s a tough one. I sympathize.

    My own gallbladder problems were primarily infectious, I think fungal, and when the infection receded so did the gallbladder problems.

    I can’t say I’m a gallbladder expert. My strategy has been to promote good bile formation with vitamin C, taurine, glycine, cholesterol; and lemon juice is a healthy solvent.

    If you’re getting pain eating fat that suggests bile formation won’t be good for you until you clear the obstructions.

    Things I would do (but I have no confidence they will work):

    1. Electrolytes. Magnesium, potassium, salt especially. Drink lots of water too.

    2. Collagen supports. Bone broth, gelatin, vitamin C, sulfur (drink epsom salt solutions). I say this because (a) this is generally important for wound healing, and (b) gallstones seem to often coincide with infections or the healing of infections, so pathogen die-off may be a trigger, and (c) die-off often seems to generate skin lesions eg acne and other small wounds and maybe some wound process is important in gallstones.

    3. Glutathione-related antioxidants. N-acetylcysteine, glutathione, vitamin C.

    4. Detox aids. If there are fat-soluble toxins going out through the bile that caused the gallbladder problems, you don’t want them to recirculate. Cholestyramine, bentonite clay, charcoal, chlorella. Try each of them once a day, cholestyramine first thing in the morning.

    I think I would string the surgeon along for a while and see if you can make progress naturally. Unfortunately it will probably take months to clear naturally, even if you find a method that works, and you won’t know if it’s working for a while.

    • Hi, Paul!

      I’m having possible gallbladder pain the 3rd trimester (I will get blood work next week). Would any of your suggestions NOT be a good idea during pregnancy? I’m drinking some fresh lemon-juice water right now, but should I be concerned about “detoxing” while pregnant? Thank you!

  3. That’s awesome Paul, thank you.

    Yes, the die-off of Lyme is a fat-soluble toxin. I was on Cholestyramine for a few days but I found it extremely constipating and after having another severe gallbladder attack by the 4th day my doctor suggested I stop taking it. Perhaps I could try introducing it at a smaller dose.

    I do take Magnesium Taurate and will try increasing my clay, vitamin C, N-acetylcysteine, and salt. I like the gelatin and bone broth idea – finally something might taste good! I assume I should be skimming off the fat first?

    Thanks again, Paul. Much appreciated.

  4. Hi DeNon,

    The magnesium sulfate is a laxative so the combination might be more tolerable. I usually use about a half-dose (2 g) per day cholestyramine and haven’t had any problems.

    There may not be so much fat that you need to skim, but you know how much you can tolerate.

  5. Thanks Paul.

    I will try your suggestions and let you know what happens.


  6. Hi Paul,

    SInce you seem to have this stuff all at the top of your head I was wondering if you knew anything about antidepressants working to relieve pain?

    With Lyme I’ve got lots of joint and muscle pain in my feet and hands, and several people have told me that antidepressants can work for that. If that’s true, I’m wondering why/how they would work to relieve this kind of pain?

    I could use some uplift of my mood as well (I’ve been sick for a long time) but have always been leery of taking antidepressants. But now people have me wondering…

    Thanks very much Paul,

  7. Hi DeNon,

    I’m afraid I don’t know if they will work for pain relief.

  8. Ok, thanks Paul. I’ll keep digging. Hope you have a great week : )

  9. i am hoping you can help me. For the past year or so, I have experience changes in my gut. I go from constipation to diarrea and have itchy skin all over, especially in private areaas. I take probiotics or drink fermented store-bought drinks in a regular basis. There have been times that I eat out and my stomach feels awful and I end up vomiting for the whole day, just to find myself with diarrea next day.
    I sometimes think I have a parasite or fungal disease. I bought a bottle of ‘fungal defense’ from Garden of Life, but I haven’t started the 14 day treatment because I feel I am self medicating. At the same time, I don’t want to visit my HMO doctor to receive a bottle of pepto bismol… any suggestions?

  10. Thank you Paul. I tried the supplements for the last week and I felt fine in my gut but the rashes persisted. Then yesterday I had a bad day and I ate some wheat (after 3 weeks of not eating any) My mood was awful and my rashes became worse. I have heard that when you try to clean your diet, you may get worse before you get better. Could it be that my gut is reacting to the changes and healing and when I had bread yesterday it got even worse? If that is the case, Is there anything I can do to help the process? By the way, I eat raw cream or goat milk once in a while, is that bad?
    Thanks for all your help!

  11. Hello Paul, I was diagnosed with IBS about seven years ago. I had a lot of bloating gas pain and diarrhea alternating with constipation. It started after I did a very stupid juice fast and properly. Afterwards I tried various things including high fiber and white with beans and fiber supplements as well as low-carb which worked for a while to relieve the symptoms. Then I had more trouble with pain and went to Paleo. This helped for a while but I noticed when I added a lot of carbs that I had trouble. Specifically very smelly and embarrassing gas. Since starting perfect health diet I have noticed some gas but not nearly so bad and no pain. But I am wondering how long I should wait for that to resolve. And when the gas is really terrible is that indicative of something that I need to seek a doctor for? Honestly it does not smell healthy and I know that sounds awful and disgusting but that’s my situation.

    Thank you for your help,

    Emily Pell

  12. Hi Paul,
    I just read your book and decided to try to go from low carb to moderate carb due to constant cravings on the low carb life style. I have been feeling more satiated since I have started adding white rice in small amounts and a slice of gluten free bread . The problem is I’ve been experiencing sudden light headedness, and daily constipation, probably due to the rice and less coffee I’ve been drinking ? I’ve been taking magnesium citrate 400mg daily, wondering if I should up it to 600mg for a while… have been taking vitamin c 1g, kelp, vitamin D-3 2000IU, Biotin forte with zinc 3mg, Vitamin K2. I love dairy so I eat plenty of cheese, cream . Not too much beef ( budget, but working in it) , mainly chicken. Veggies and dark chocolate rounds out my diet with some desserts I make from almond flour. I’m working in incorporating liver and bone broth and more fermented veggies and trying to wean myself off of coffee, I seem to be very sensitive to caffeine.
    My question is how do I not have Constipation? And do you think it’s ok to have plenty of dairy? ( I make a cristless quiche so breakfast is a 1/4 of a quiche which would be 1/4 cup each cream and half and half, 1/4 cup shredded cheese, some buggies of ham, 1 egg. I never had any problem before only since I started adding safe starches . Oh and one more question: what is your take on gluten free breads? Mainly made of rice and potato flours?
    Thank you so much !

    • Hi Gabriella,

      I’m not sure why you have constipation; maybe Paul will have some ideas.

      To answer your other questions — Dairy and gluten-free breads made from rice and potato flours are both allowed on PHD in moderation (for example a single glass of milk per day, or a couple of slices of glute-free breads per week). It doesn’t sound like a serving of your quiche has too much dairy for one day, but it does contain fairly high-fat dairy (so you’d want to minimize other added fats).

      Probably rice + potato flour breads are better than almond flour breads, since it would be easy to get too much polyunsaturated fat if you bake with almond flour.

      Keep in mind that natural whole foods like potatoes are rich in micronutrients and fiber too, while baked goods made from potato flour contain only starch; whole foods also have a better effect on the digestive system than flour-based products (see for example the discussion here: So it’s better, for example, to eat steamed potatoes than bread made from potato flour.


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