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What Causes Candida Overgrowth? Is It Diet?

Candida overgrowth or infection is the hallmark of an overstressed immune system.

C. Orian Truss, M.D.

This post is part of a multi-part series, both written and in audio form on the podcast, aimed at helping people find root causes of common chronic ailments plaguing Americans right now. We’ve covered IBS, mold illness and chronic fatigue, prostate issues, UTI, uric acid, and more.

If you’ve arrived here, you’ve probably been all over the internet looking for answers – the candida issue is a rabbit hole and a half- but hopefully you’ll find a few nuggets of wisdom here that help you along the way.

You might also like the post Leigh did on the best probiotics for beating back candida.

Everyone has candida

As with the ubiquitous nature of histamine, the first point to make here is that candida albicans is a normal part of a healthy microbiome and it lives inside all of us, usually co-existing with all of the other microbes in our gut.1 Problems ensue when the microbial balance in the gut is altered and candida spreads beyond its assigned borders.

The usual result in these cases is an acute infection of the oral cavity or urogenital area. The modern day holistic view that all ailments come back to “candida” is plausible as a theory, but is not based on any overwhelming evidence. Much of the candida science you’ll read is based on hunches extrapolated from the candidiasis research.

Most common causes of candida issues

You probably already know that sugar feeds Candida, and that a depleted microbiome, often as the result of repeated antibiotic use, allows Candida to spread and do damage in the gut. That’s the 10,000 feet overview. But what causes the microbiome to go haywire in the first place? 

Most people will tell you these are the most common culprits that cause issues with candida:

  1. Antibiotic use (human study)
  2. Birth control (human study) (human study)
  3. Eating a high carbohydrate and high sugar diet (mouse study)
  4. Stress and chronic high cortisol (rat study)
  5. High carb diet and poor blood sugar clearance (no good studies)

Here’s the thing though – when you break down the “what causes candida” studies used by the internet echo chamber, many are in rats and mice.

The best of these studies teach us that the main culprits for candida’s spread to unhealthy levels are birth control pills and antibiotics.

Diagnosing Candida Overgrowth

What are the tests people use to diagnose a yeast overgrowth?

Home spit test

Less than scientific, but popular. First thing in the morning you spit into a glass of filtered water before eating or drinking anything, or even brushing your teeth. Wait 20 minutes to see if you find “strings” coming down from the water’s surface, which is thought to be a sign of Candida overgrowth.


Candida emits toxins into the body, and gliotoxin is one of them. When Candida is running amuck, gliotoxin levels can be elevated.2 And guess what, gliotixin is an immunosuppressant. Multiple sclerosis patients often present with elevated gliotoxin.3 However, there is controversy over whether Candida causes elevated gliotoxin levels. Some believe high levels of gliotoxin in the urine is a sign of mold exposure and colonization, with Candida present as one of a few fungal invaders. 

Living in a moldy building will cause your gliotoxin levels to go up, and the folks that run one of the best known labs for testing gliotoxin don’t even list Candida as one of the causes for out of range results.

Although it’s a clue, you can’t 100% say you have Candida overgrowth just because you have elevated gliotoxin. Having said that, elevated gliotoxin does signal an issue with mold toxicity, so the protocol for healing will be similar, but not identical. Dr. Nathan and colleagues have different treatment protocols set up for the various mycotoxins found lurking in the human body. 

IgG, IgA, and IgM Candida antibodies

Are Candida antibody tests reliable for diagnosing an overgrowth? Many on the internet seem to think so. And yes, you can test for elevated Candida antibodies, BUT 20-30% of healthy adults will test positive (presumably because Candida is commonly found in healthy individuals), so this isn’t necessarily a conclusive test either. As with gluten sensitivity tests measuring for tissue transglutaminase antibodies, those with suppressed immune systems may show up with a false negative, if for example, their serum IgA levels are low.

Stool testing

Comprehensive stool testing can measure for yeast overgrowth, among other things.

Urine Organix Dysbiosis Test

Candida releases over 70 different toxins. One of these is D-Arabinitol, which the Urine Organix Dysbiosis test measures for.4

Practical testing considerations

Since none of the methods for diagnosing Candida listed above are 100% foolproof, most clinicians believe we should use a “preponderance of the evidence” analysis when diagnosing Candida.

If you have intense sugar cravings, digestive issues, aching joints, positive labs for leaky gut, and elevated gliotoxin on top of it all, we can make an educated guess that there is an issue with your gut health, and Candida could be one of the contributing factors.

Candida diet is not a ketogenic diet

Also, as I mention above, the dietary protocol for treating Candida and for treating mold is often very similar, with many people struggling to detoxify from mold exposure turning to a low amolyse diet. Amolyse is an enzyme that converts starch to sugar, and sugar is what we want to avoid when beating back fungus. Side note: this does not mean a ketogenic diet is the answer. Some studies indicate Candida can thrive on ketones.

Ok, so you’ve run the gauntlet of tests and believe you could be suffering from an issue with yeast.

What do you do to treat the problem?

Lesser known causes of candida overgrowth

In this section, we want to highlight an interesting paper, titled Restoration of Immunologic Competence to Candida Albicans, written by C. Orian Truss, M.D., that offers unique insights into the yeast overgrowth problem. Dr. Truss’ paper is especially appealing because it offers multiple theories of Candida causes, rather than one uniform / dogmatic rule. I also borrow from the research of Dr. Neil Nathan and his new book Toxic (View on Amazon), which is a good read for anyone battling chronic pathogen related issues. 

The purpose of this list is to address, what for some people, will be the root cause of their yeast problems.

Ask yourself: why has Candida reached unhealthy levels in your gut? Taking a supplement like oregano may beat back some of the yeast for a time, but will it stop the process that gave rise to the infection in the first place?

We want to rip up the yeast overgrowth at the roots so it won’t come back.

Mold in the environment

Many molds that do not exist within the body have some degree of cross antigen-icity with Candida albicans. Patients often notice aggravation of symptoms in environments characterized by a high count of mold spores.

Dr. Truss

We’ve given him a little flack on the blog over what Bulletproof coffee does to some people’s lipid markers, but this is an area where Dave Asprey is solid. He has been sounding the alarm on the dangers of mold for years now with documentaries like MoldyIt was Dr. Truss’ paper that first turned me on to the idea that Candida is cross reactive with other species of mold, so if you’re having issues with Candida, it could be a problem with the air in your home, or even the air in your city. Based on Dr. Truss’ theory, Candida symptoms can fluctuate based on mold exposure, so do a thorough audit of your environment. 5 

Allergy to cereal grains

Many patients are allergic to the cereal grains, while others exhibit an abnormal response to carbohydrate in the glucose tolerance test. Carb restriction may eliminate such food antigens from the diet, and also may correct the excessive insulin response that results in hypoglycemia.

Dr. Truss

Although Dr. Truss mentions allergy to cereal grains as a potential cause of Candida overgrowth, again citing the potential for mold in these crops, that are grown in bulk, and then stored in bulk where mold can grow, the issue here is more likely intestinal permeability and blood sugar spikes than it is mycotoxin. If this seems like a bridge too far, keep in mind that celiac disease is an autoimmune reaction to grains, and it’s on the rise, with incidents of celiac rising by 400% in the last 40 years. 

It is also undisputed that mold inhabits our human grain supply, it’s just another area where government regulators tell us what are “safe levels.” Ochratoxin A, a sinister mold toxin, has been found in our breakfast cereal.6 

This is an easy test to run – cut out all grains for a month and see how you feel. If the issue goes beyond grains to an “excessive insulin response” as Dr. Truss argues, perhaps it’s worthwhile to look at markers like HbA1c, or a glucose tolerance test to see how the body is reacting to glucose immediately after a high glycemic meal in what is known as the “post prandial” period.


Many Candida infections are secondary to allergic responses of the mucous membranes of the respiratory tract, urethra and bladder.

Dr. Truss

Candida becomes invasive most often in two regions of the body: the intestinal tract and the vagina, or urogential area. Guess what? This is also where mast cells, the cells that release histamine, are found in highest numbers.7 Mast cells don’t just release histamine, they release an inflammatory cocktail of immune cells to combat invaders.7 However, when these substances are chronically released, they cause inflammation.

In essence, Dr. Truss is saying that the process of local mast cell degranulation, over long periods of time, weakens tissue, which invites Candida. Toxins released by the yeast degrade the immune system further, which makes the local infection more difficult to combat. The idea of Candida being “invited” into a region of the body is not without precedent, even on this blog. I recently wrote a men’s health post on prostatitis which featured a study finding that many young men who believe they have prostatitis actually have yeast infections, and it’s E. Coli that allows the yeast to spread to the bladder and prostate in the first place. 

Consider this case study of Interstitial Cystitis (IC) being successfully treated with an allergy protocol. For those who don’t know, IC is a chronic inflammation of the bladder, which usually occurs in women. The case study called IC “one of the allergic disorders of the urogenital system,” and that is exactly Dr. Truss’ point: traditional allergy can inflame tissue which invites Candida. This leaves allergy shots and drops, or moving to a location where no airborne allergens are present, as options for treating Candida.

Hormone and thyroid imbalance

Endocrine or other metabolic abnormalities may impair the immune response, hypothyroidism being a common example.

Dr. Truss

Again, another one that makes sense in light of what happens when people develop a thyroid issue, which are autoimmune conditions. When the immune system is attacking the thyroid, presumably, it is also causing inflammation, just as chronic mast cell activation does with traditional allergy. The resulting weakening of the immune system invites the spread of pathogenic bad guys like Candida, which are also immunosuppressants.

Depleted microbiome after antibiotic or birth control use

Repeated courses of antibiotics and birth control pills, often punctuated with multiple pregnancies, lead to ever increasing symptoms of mucosal infections in the vagina and gastrointestinal tract.

Dr. Truss

Avoid oregano? Thought it was great for Candida? Well, that’s what the echo chamber would have you believe, but the data isn’t overwhelming in favor.

For a reliable anti-fungal, Nystatin seems to be the best option, both spray and pill form according to Dr, Nathan.

If you’re first looking to go the nutraceutical route, my thinking is don’t do more damage to an already depleted gut with an “herbal broad spectrum antibiotic” that will continue to destroy the good bacteria along with the bad. It was the antibiotics that got you into this mess in the first place, so why take more?

Oil of Oregano has shown some limited promise in treating Candida in vitro, but it doesn’t stop at attacking fungus, it’s a powerful antimicrobial agent across the board.

This study in mice found that oregano oil stopped the growth of Candida.8 This in vitro study is often cited as well.

An oregano supplement has the potential harm healthy flora in your gut, and for this reason, it could actually make a Candida problem worse over the long term.

However, despite the fact that the “internet echo chamber” has concluded that oregano is a must have for fungal overgrowth, there aren’t a ton of studies that show efficacy. For example, the Dr. Axe article referencing oregano oil’s ability to kill Candida cites to this study. However, that study mentions oregano’s potency as an antimicrobial, but Candida isn’t listed as one of the pathogens successfully targeted:

dictamnus  (oregano) essential oil and its main components were effective against Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, Listeria monocytogenes, Salmonella Enteritidis, Salmonella typhimurium, Saccharomyces cerevisiae, and Aspergillus niger.

Dr. Axe’s primary experience with Candida seems to be as an effective yeast overgrowth treatment for his mother, which is fantastic, but not enough to up the science grade. This comprehensive Candidiasis page on the University of Maryland Medical School website doesn’t even mention oregano as a natural treatment for Candida. Tea tree oil, probiotics, garlic and others are all mentioned. Not to say that oil of oregano doesn’t kill Candida, it might, just suggesting you tread with caution as oregano can also kill “friendly” bacteria as well, and it’s the friendly bacteria that are there to keep Candida in check in the first place.

many mold docs believe very small doses of agents like activated charcoal, chlorella, s. boulardii, and bentonite clay, which all bind to mycotoxins, are a better bet for candida than are ant microbial agents.

As always, check with your health care provider before starting or stopping any supplement regimen. 

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Closing thoughts

A big part of treating a Candida overgrowth will be to avoid sugar like the plague, especially at first.

Beyond that, I hope this article and Dr. Truss’ work offered up some relatively novel theories as to why some people may be prone to developing a Candida overgrowth in the first place.

Dr. Aaron Gardner, BSc, MRes, PhD

Dr. Aaron Gardner, BSc, MRes, PhD is a life-scientist with a strong background in genetics and medical research, and the developing fields of personalized medicine and nutrition. Read his full bio here.

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Leave Comment

  1. Brooke Y. says:

    Super helpful. Explains a lot about what I’m dealing with and gives me specific direction I can have confidence in. I’ve been going around this block a long time, seeking, studying, trying things and getting sicker. Now I have solid direction, understanding and hope! Priceless!

    Thank you.

  2. Terry says:

    Hello and thanks for the great info! My boyfriend was ill and took a very strong antibiotic, then developed a rash on his skin (little bumps most everywhere, especially on his inner thighs and near his armpits. He has not been able to get rid of them, although it has been months. His doctor said it is a candida overgrowth and prescribed antifungal creme and shampoo. We are wondering if anyone else has had this, and how long it took to get rid of. He doesn’t want to continue with the doctor’s recommendations as they don’t seem to be working. He is now willing to quit sugar, grains, fruits and start taking a probiotic after reading your advice (none of which the dr. said anything about). Do you know of anything else he needs to do for this particular candida skin rash?

  3. Mark P. says:

    I believe I can attest to the potential for Oil of Oregano for upsetting the microbiome and facilitating the overgrowth of candida. In January of 2018 I decided to commence a course of Oil of Oregano for what I thought would be a gut health tune up. I ran it for about a month if I recall correctly. About 2-3 weeks after discontinuing the course, I began to experience acute nausea, vomiting, and diarrhea whenever I consumed even very modest amounts of dietary sugar. (We’re talking healthy sugar like Japanese sweet potatoes, not candy) I’d never experienced problems like this in my life. My already significant problems with insomnia grew much worse. Sixteen months later the problem has grown steadily worse. Now I cannot tolerate even tiny amounts of sugar such as 8 grams of organic maple syrup which getting very nauseous 3-4 hours later. The only supplement that appears to help is S. Boulardii.

    To anyone reading this post, please be very cautious with Oil of Oregano.

  4. CandiWarrior says:

    I have a few questions about NAC for candida

    Does it count as a binder? I’m taking activated charcoal, should I discontinue this when I take NAC?

    When do I take it? With antimicrobials or with probiotics or with vitamins?

    I’m taking so many things for this candida its making my head spin.

    • According to Dr. Neil Nathan, bentonite clay and not charcoal is the best binder along with Sacro B., for gliotixin, but you have to confirm through a mycotoxin panel that you do indeed have elevated gliotoxin. Dr. Nathan also lists NAC as part of his gliotoxin regimen. It isn’t a settled matter, but many believe elevated gliotoxin is a sign of Candida.

  5. Simply RAW says:

    I just want to THANK YOU for taking the time to share your knowledge. It is by communication that we all stand to gain. Living in Florida where I smell mold almost everywhere! It is so sad that many doctors here either don’t know or just choose to keep treating “symptoms” instead of getting to the root of the cause. I wish I could move north to escape the effects of the airborne mold inside/ outside in cars ects…. I always feel better when I leave Florida for a week or more. Once I return home it is just a mere few days (less than a week) where my arms start to itch all my joints ger stiff and sore as well as my hair gets dull feet get dry and cracky and I lose my breathe in a short amount of time! And I too get brain fog. No real sense in treating for any of these for Mold is here and it’s gonna stay. You can even see the differences in skin southerners vs northerners its not from sun damage its from the funguses we live with.

  6. Carol says:

    Excellent article. Succinct, well-researched and focused. Really glad I found you and it. I first noticed a white tongue in January 2017 after multiple UTIs (E. coli) over 4 or 5 months treated with broad spectrum antibiotics (amoxicillin 🙁 ) . I had checked for evidence of Candida overgrowth before but never really had any of the symptoms. I was just wondering today why I kept having recurrent UTIs… I knew the candida was somehow related to them. So thanks for clearing that up! I wound up, naively, throwing everything but the kitchen sink at the Candida, mostly a big bowl of cultured yogurt taken simultaneously with two or three Gr8t acidophilus probiotics… three times a day. Plus raw garlic, aloe vera, and a few other things that escape me now. Very shortly after doing the cultured yogurt/acidophilus protocol I had an EXTREME herxheimer reaction (Nothing I had read had warned me about that with what I was taking)… and I was unbelievably sick for 9 straight days. Huge amounts of urination, night sweats, chills, diarrhea,102 fever every night, couldn’t eat, lots and lots of shooting pains in my brain (which I finally did remember that I had read could happen with acetylaldehyde during die off… which is how I finally figured out what was going on, I was pretty scared), balance problems, tending to list to the right and kind of walk in circles. Etc Etc. Toward the end I did pass what must have been two biofilms (or one that had broken in two)… that came from higher up in my digestive tract. I was all alone and in Mexico, so no quick access to things like pantothenic acid or molybdenum which I later learned would have helped with the die off symptoms. Oddly, a month later, I had 1 cup of cultured yogurt by itself and had the same symptoms for 3 or 4 days. So I didn’t touch cultured yogurt for a long time! after that I completely eliminated sugar, which I didn’t really consume a lot of, and alcohol… and refined carbs. Over the months the coating on my tongue almost went away; it was very faint. And I haven’t had any more UTIs. However, I did resume eating some ice cream and some chocolate and desserts during recent times of stress (still no alcohol) and the white coating is back. 🙁

    So here’s my question for you please. I believe that the extreme die off was due to toxic overload from the break up of the candida biofilm in my intestines. Once it was eliminated, I finally began to feel better. It took a while to get back to 100%…. it was a horrible ordeal.

    Now I am really leery of doing anything that would cause that again.

    Is there a way that you’ve read about to break up the biofilm “slowly”? Or is it always catastrophic? Is there a way from testing to determine if I have a biofilm again? Is the protocol that you describe effective in breaking up biofilms, or does something else like Interphase Plus have to be taken?

    Intestinal biofilms seem to be the big problem in chronic candida, but there’s not a lot written about really effectively eliminating them without excess toxicity. Most research for candida biofilms is focused on medical implants, catheters, etc.

    Thanks again for the article and any thought you might have re my questions.

  7. Sharon says:

    I was a patient of Dr. Truss in the 1990’s. After numerous trips to specialists to find out what I did not have, and after reading the Missing Diagnosis and believing it was an autobiography, I visited him and went through the battery of tests given by Kenny.

    Soon, I was home taking Nystatin and giving myself injections twice a week, calling Juanita every Monday morning to report progress or lack thereof and then hearing back later in the day to see how to adjust my dosages.

    3 years later, I was 90% better. Chemical sensitivities were still somewhat of an issue, and there were still days of dysentery if I tried to eat something I should not.

    Near the end of my time as a patient, Lederle stopped making Nystatin, and the new company was just different enough to make it impossible to keep it down. I had to stop taking it and look for something else. At this time, I moved to SoCal and away from the moldy South. My new house in West Hollywood obviously did not have a mold issue. It turned out that mold was mostly responsible for 50% of my issue. The other 50% came from antibiotic and corticosteroid prescriptions being taken on top of each other, with declining health from that point on.

    Dr. Truss understood that I was interested in research. He showed me where he had successfully cultured candida in petri dishes containing caprylic acid and other materials marketed for the use against candida, and thus he did not have much faith in these products. He believed in Nystatin, candida injections combined with other allergens, a diet limiting carbohydrate consumption to 80 grams a day with it coming mostly from vegetables, and avoidance of molds. Aspergillus was my kryptonite.

    I am basically free of candida overgrowth today. I am married to a wonderful ex-athlete 10 years younger than me, and I have no problem running rings around him with my return to health. I was a collegiate athlete and had to give up basketball my senior year when I became ill.

    Today, there are a couple of health food stores that give people my contact information. I estimate that I have helped about 45 women and 10 men discover that candidiasis may be the cause of their suffering. The first thing I tell them is to check for mold issues. A large number of the people I talk to live in basement or first floor apartments or condos. As far as I know, nobody I have counseled has lived in an upstairs end unit of an apartment or condo.

  8. Mary says:

    I’d love to be able to take S Boulardii but I’m allergic to yeast and I get lightheaded when I take it. I’ve taken a lot of antimicrobials for Lyme and coinfections and I believe that has flared yeast for me. I have a high gliotoxin level also.

    Is there some way a person can take S Boulardii if they are allergic to yeast? Maybe an allergy shot for bakers yeast perhaps?


    • Mary,

      Bakers yeast is S. cerevisiae, which is a different strain than S. boulardii. Maybe an allergist would know the answer? I am not sure if they administer allergy drops or shots for S. boulardii, but it’s an interesting question for sure.

      • Debra Rowe says:

        To Dr. O’Connor, we moved into a new home in Sept, I immediately was sick when we closed up the house. We had Air Quality Specialist come in. Our basement, refinished with carpet, had yeast test come back Too Numerous To Count. We had the house gased, and had mold removed (we had black mold, Aspergillus and Penicillius) . Our house is still DUSTY, I’ve had numerous tests, nothing, but am still so ill I stay in bed a lot. I have chronic cough with watery phlegm, bowel problems (stool with white yuck on it) , chills, always cold, mouth always tastes like I drank a bad chemical, just tired and fatigue I can’t shake, a yeasty smell under my breasts (alcohol rub solved that). Could it be yeast? My Drs. have diagnosed me with anxiety, who wouldn’t be? We went on vacation for a week and I felt great! Lung issues kept me up the 2nd night. Help!!! Am I just crazy? Very Sincerely, Deb Rowe


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