I love the Internet as much as the next girl, but it has not been an unequivocal blessing. For all the wonderful things the Web has facilitated – Google, Skype, free two-day shipping from Amazon – there is a downside to cyberspace, too. To clinicians like me, one of the greatest online nuisances is the platform that the Internet provides to disseminate health misinformation couched in pseudoscience.
One of the more common online health fictions I encounter is that of a mythical condition called "Candida overgrowth." I've been confronted enough about this purported condition by misinformed patients that I've decided it's finally time to set the record straight.
You may not have heard of Candida albicans – a species of yeast – but you almost certainly harbor it in your digestive tract. Exposure to Candida is so universal that doctors sometimes use skin or blood tests that measure response to Candida in order to verify that one's immune system is working properly.
Specifically, a well-functioning immune system would be expected to mount a response to a foreign protein that's so ubiquitous in the environment. Furthermore, Candida is a normal member of the human gut flora – the trillions-strong community of microscopic yeasts and bacteria that reside in our bowels. In other words, it's supposed to be there.
[Read: Tending Your Inner Ecosystem.]
Despite the fact that "having Candida" is universal among healthy humans, there's a lot of talk circulating online about this species of yeast, implicating it in a host of undesirable health conditions, from headaches, joint pain and fatigue to weight gain, food cravings and allergies.
Patients have come to me on a "yeast-free" diet because they've read it will improve their chronic digestive problems or recurrent vaginal yeast infections. Sometimes, patients report that a holistic practitioner has diagnosed them with "overgrowth" of Candida in the gut, which they believe to be responsible for their chronic bloating or irregular bowel movements. When they show up in my office, however, they remain symptomatic despite following the so-called "Candida diet" they were prescribed.
So, is there anything to these accusations against this much-maligned species of yeast? Let's examine some well-established scientific facts:
• Fact No. 1: Candida infections can and do affect certain parts of the body – but generally not the intestines. Candida infection – called candidiasis – affects the skin and specific mucous membranes including the vagina, mouth and esophagus.
[Read: Vaginas and Vulvas 101.]
The type of cells lining the intestine, however, preclude the invasion of hyphae, the branching tentacles that enable fungi to penetrate and colonize a tissue. Candidiasis is an opportunistic infection that generally occurs after antibiotic use or when someone is immunocompromised – as in the case of AIDS, cancer or critical illness.
Newborns are also susceptible to Candida infections in their diaper area or mouths (oral thrush) due to their underdeveloped immune systems and may transmit yeast infections to the skin of their mothers' nipples when nursing. (Ouch!)
For the reason described above, Candida does not infect the small intestine nor does it overgrow in the colon. In fact, searching the term "Candida overgrowth" in PubMed, the national database of over 22 million published biomedical research studies maintained by the National Institutes of Health, turns up nothing. Unless every medical researcher who studies Candida, digestive health, infectious disease or immunology is in on a conspiracy to hide the truth, it's pretty safe to say that "Candida overgrowth" is not an actual phenomenon.
[Read: Examining Food Myths and Facts.]
If this doesn't convince you, consider this: A Candida infection of a mucous membrane is visible to the naked eye – it looks like plaques of cottage cheese and there's no missing it. If a doctor scopes your GI tract and doesn't see a Candida infection, then you don't have a Candida infection. There's no such thing as an invisible Candida overgrowth; if you had it, a doctor would see it plain as day.
• Fact No. 2: The Candida you do have in the colon does not cause gas or bloating. Here's a fun fact about basic fungal metabolism: Unlike bacteria, yeasts do not produce hydrogen or methane gas as a byproduct of metabolizing nutrients in the oxygen-poor environment of the colon. Instead, yeasts produce carbon dioxide, a gas that quickly diffuses into the bloodstream and is exhaled by the lungs.
You could harbor a pound of Candida in your colon, and it still wouldn't make you flatulent or bloated – the carbon dioxide doesn't sit around in the colon long enough. In other words, if you've got excessive wind or bloating, blame it on a bacteria, not a yeast!
• Fact No. 3: If you suffer from chronic yeast infections, eliminating "dietary yeasts" won't help. There are over 1,500 different species of yeasts within Kingdom Fungi. The yeasts used in food fermentation, from bread baking to beer making, are generally from Saccharomyces species, not Candida. So, just as the Lactobacillus bacteria used to culture your yogurt could not cause a Salmonella infection, so too a Saccharomyces-containing food like bread, beer or sauerkraut cannot cause (or worsen) infections caused by Candida.
• Fact No. 4: You don't have Candida in your blood. Or perhaps it's more accurate to say that if you did have Candida in your blood, you'd probably be in an Intensive Care Unit fighting for your life, not walking around with a "foggy brain" or bloated belly reading this article.
Websites dedicated to the fiction of "Candida overgrowth" allege that Candida can leak through the gut wall and enter into the bloodstream, causing headaches, depression or other systemic symptoms. This claim is patently false. Unless the skin or gut membranes are broken by trauma or punctured by hardware, fungi cannot just slip out into the bloodstream and hitch a ride around one's body.
Blood does NOT harbor yeast in otherwise healthy, ambulatory people. When yeast does manage to find its way into the bloodstream, it results in a life-threatening condition called fungemia. A person couldn't walk around with fungemia for very long without falling critically ill, and adopting a sugar- or yeast-free diet certainly is no substitute for ICU care.
[Read: U.S. News Best Hospitals 2013-14.]
So what of those tests your naturopath ran which s/he used to diagnose your alleged Candida overgrowth? They may be antibody tests that confirm nothing other than that you have been exposed to Candida environmentally, and your healthy, well-functioning immune system appropriately developed antibodies against it, as it does for all foreign proteins. Or they may be stool tests that show, under a microscope, you indeed harbor Candida in your colon ... as would be expected.
Of note, there is no established "normal" value of Candida in the gut; therefore, interpreting any test result as indicative of an abnormally high value of Candida lacks scientific validity.
To be sure, I have no particular love or affinity for Candida as a species; as is the case for three-quarters of women, Candida has given me my fair share of grief. So, it's strange to find myself in the position of defending Candida against the online smear campaign that's been perpetuated against it.
Why do I even bother? Because the Candida hoax is a diversion that leads people with real digestive distress further away from discovering the true cause of their symptoms, thereby prolonging the time to a proper diagnosis and effective treatment.
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Tamara Duker Freuman, MS, RD, CDN, is a registered dietitian whose NYC-based clinical practice specializes in digestive disorders, celiac Disease, and food intolerances. Her personal blog, www.tamaraduker.com, focuses on healthy eating and gluten-free living.
Please note that the author cannot offer individualized medical advice to readers who contact her via email.