Candida Cleanses: Are Anti-Yeast Diets Just a Fad?

If your patients are regular visitors to certain popular nutritional-lifestyle websites, they might have heard some alarming news — their stomachs are teeming with Candida and it's wrecking their health.

On Goop they can find an interview with physician Amy Myers, who estimates that 90% of her patients, and approximately half of all women, have an overgrowth of this yeast. Courtesy of Dr Oz, they'll learn that Candida overgrowth is likely causing their chronic fatigue, fibromyalgia, or spastic colon. The constellation of symptoms attributed to the fungus is so wide-ranging that mainstream news publications have labeled the diagnosis as pseudoscience.

Yet, according to other websites, the only hope are what have been variously termed "anti-Candida diets," "anti-yeast diets," or "Candida cleanses." These dietary interventions share a common goal of curbing or eliminating the sugars and carbohydrates that have been linked to Candida growth. Take aim at these components, the theory goes, and you'll starve the Candida that's at the root of your health problems. There's even a celebrity endorsement of this dietary approach via actress Rebel Wilson, who attributes it to her recent 60-pound weight loss.

Candida's increasing reputation as a gastrointestinal (GI) menace has led to a counterresponse from concerned experts, who say that opportunistic forces are turning a largely benign and common fungus into fodder for fad diets.

One such critic is registered dietician Abby Langer, who was alarmed enough about discussions she saw about Candida overgrowth to write a critical post of it on her popular blog in 2020.

"Candida in the gut is real, but the prevalence is often overstated by people who want to sell something," Langer told Medscape Medical News. "This is a great example of how some providers or even just random people use fear to sell a product. Clearly, it's not something that a reputable professional should be doing."

Candida as Culprit: Debunking Misinformation

Those who know Candida best are happy the general public wants to know more about it; they just want its depiction to be accurate.

Among these experts is Mahmoud Ghannoum, PhD, who has spent several decades as a mycologist trying to convince people of the importance of fungi in human health.

"I like people to think about fungus. But, I don't like them to think, 'Oh my God, Candida causes everything,' and to focus on the social media [aspects of the story], which are not real," said Ghannoum, director of the Center for Medical Mycology at Case Western Reserve University in Cleveland, Ohio, and author of Total Gut Balance: Fix Your Mycobiome Fast for Complete Digestive Wellness.

Ghannoum said there's plenty of emerging data supporting Candida's role in various conditions, including recurrent vaginal yeast infections, inflammatory bowel disease, Crohn's disease, and arthritis. However, data are comparatively limited for some of the more opaque symptoms.

"As a cause of fatigue, brain fog, and those sorts of things, I don't think there's a lot of evidence," he said.

As researchers work to elucidate Candida's role in human health, it's important to remember that it largely functions as a benevolent force in our GI tracts, Ghannoum added.

"Having Candida in the gut at low levels can be beneficial for breaking down food, and the by-product is creating beneficial bacteria that helps symbiosis," he said.

Most humans' GI tracts get colonized with Candida at or around birth. From an evolutionary perspective, Candida's presence may have educated our immune systems against infection from such organisms as Clostridioides difficile. Murine evidence suggests it may even have antitumor effects.

The hundreds of Candida species we play host to mostly function as harmless commensal organisms. Just five species of Candida account for >90% of all infections, the most common strain being Candida albicans. The yeast's pathogenic possibilities are usually only unlocked when the ideal conditions present themselves, such as when patients are taking antibiotics or are in an immunocompromised state, allowing C albicans and other Candida species to overgrow and cause infections (known as candidiasis). The most commonly encountered infections, such as thrush and vaginal yeast infections, are easily treatable. Although less frequent, hematogenous Candida infections have well-established and deadly implications, with mortality rates surpassing 40%.

Critics argue that proponents of Candida diets and related products are having it both ways — exploiting its rare, but serious, clinical manifestations, such as candidemia, to make a case that even its benign presentations are cause for concern.

"Candida in the blood is a life-threatening condition," Langer said. "If you had it, you wouldn't be walking around living your life; you'd be in the ICU."

The Centers for Disease Control and Prevention estimates that 25,000 cases of candidemia occur every year. The most common treatment for it is antifungal medication, not dietary interventions.

Even rates of noninfectious Candida overgrowth are often overstated, according to Ghannoum. As yet unpublished data from stool analyses conducted at the medical company he founded, BIOHM Health, place the percentage of those with Candida overgrowth around 2%.

In an interview with Medscape, nutritionist and author Lisa Richards, CNC, creator of The Candida Diet website, said she and her colleagues' research indicates that overgrowth levels are quite a bit higher. Richards cited data showing that approximately a quarter of patients with unexplained digestive problems have small-intestinal fungal overgrowth. One analysis of positive fungus samples taken from the guts of those with chronic GI complaints revealed an 84% rate of C albicans and 16% rate of Candida glabrata.

"There has historically been an insistence that this type of fungal overgrowth could only happen in patients who are severely immunocompromised," Richards said. "These studies show that it's possible, and indeed relatively common, for it to happen in those with more healthy immune systems too."

Are These Diets Really a Cause for Concern?

The majority of the advice on The Candida Diet website, and in other popular Candida-directed interventions, would likely find support among most clinicians.

"The Candida diet has a strong emphasis on removing processed foods, cutting added sugar, and increasing probiotic foods," Richards told Medscape. It also asks participants to abstain from alcohol and to rely heavily on fruits, vegetables, and lean proteins.

Unlike other common anti-inflammatory regimens, these diets advocate excluding glutenous grains like wheat. Richards cites evidence that gluten can negatively impact gut microbiome diversity as a reason for incorporating this element. However, other research suggests that the elimination of gluten has no value and can even be detrimental in those without celiac disease or other known sensitivities.

If experts balk at some of the claims behind Candida overgrowth and diets meant to address it, they don't deny that studying its role in the gut is an area of promising research.

According to Ghannoum, Candida's ability to breach the gut barrier and cause a host of problems has been evident since at least the 1960s, when a German researcher ingested a test tube with this fungus and nearly died as a result.

More recently, the C albicans researcher Carol Kumamoto, PhD, professor of molecular biology and microbiology at Tufts University in Boston, presented evidence that in certain instances, Candida can migrate beyond the human GI tract and become an opportunistic pathogen elsewhere in the body.

"Studies show that the same strain of Candida can be detected in both the blood and the GI tract of patients, arguing that the infection arose from the strain that was colonizing the GI tract," Kumamoto said.

There is also emerging evidence that Candida's presence can be affected by adjusting diet. Mice fed coconut oil, which is rich in medium-chain fatty acids, show reduced GI colonization by C albicans compared with those given diets rich in beef tallow or soybean oil. A separate study in preterm human infants also showed reduced colonization in those given medium-chain triglyceride supplementation. Conversely, neutropenic mice given higher levels of glucose in their drinking water have correspondingly higher rates of C albicans.

Decades spent studying Candida has taught Ghannoum to respect its destructive possibilities.

"It's an opportunistic organism, so you don't want to give it the tools to become even more so," he said. As such, he generally supports dietary interventions designed to reign it in.

"I'd like to encourage the growth of beneficial organisms and reduce the pathogenic ones. The diet that can lead to those end objectives is the way to go," he said.

It's also an approach that Kumamoto said she backs, so long as the dietary changes are not extreme.

"I would not be in favor of trying to eradicate Candida from the body [in the absence of an infection] because having a low level of Candida in the body is normal for people," she said.

For Langer, however, it's a mistake to characterize these diets as relatively benign. For one, she thinks doing so could keep patients from getting properly diagnosed for what's actually causing their underlying symptoms, such as small-intestinal bacterial overgrowth.

But Langer also fears the repercussions of turning a blind eye to what she sees as the shoddy foundation upon which they've been built.

"I've worked as a dietitian for over 20 years, and I've seen so much nutrition misinformation causing people anxiety about their bodies and about food and eating," she said. "Sure, Candida diets may not be physically dangerous. But what about the psychological dangers of being told that harmless foods are dangerous and responsible for causing your [GI problems]? We can't downplay the role that misinformation plays in our health."

John Watson is a freelance writer in Philadelphia, Pennsylvania.

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