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What Causes Candida Overgrowth? Is It Diet?

Candida albicans

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. 

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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