Some people believe that having too much yeast in your system causes a number of symptoms and contributes to multiple chronic health problems.1 Yeast is a type of fungus. Fungi—mostly Candida—can be found in the stomach, end of the small intestine, and large intestine of about 70 percent of adults.2 In fact, your digestive tract is full of microorganisms (bacteria, fungi, and viruses). This community of microorganisms is called the microbiota, and scientists are just starting to understand their role in your health.
Anti-fungal diet: The claim
When the microbiota is healthy and your immune system is working well, Candida is a harmless guest in your gut.2 There are far more bacteria than fungi in your gut, and the good bacteria keep the fungi under control.2 However, taking antibiotics or having a disease that affects your immune system can affect the balance of your gut bacteria. As a result, you may have an overgrowth of Candida. Some people think that other medications, nutritional deficiencies, too many starches, and sugars, and environmental molds or toxins can also cause an unhealthy change in your gut microbiota that leads to excess Candida.1,3
The theory is that your health will improve if you get rid of the extra fungi and re-introduce good bacteria into your digestive tract. A simple internet search turns up dozens of websites explaining how to treat fungal overgrowth. Typically, the solution includes:1,4,5
Diet low in sugar, yeast, refined carbohydrates, and mold-containing foods.
Probiotics from yogurt, fermented foods, or supplements.
Non-prescription antifungals, such as oil of oregano, garlic, and grapefruit seed extract.
Prescription anti-fungal medications (recommended by some practitioners, but not all).
Many of these websites include lengthy lists of foods to eat and avoid. The basic idea is that sugars feed the yeast and must be avoided. Therefore, anti-fungal diets eliminate:
Added sugars (examples: cane sugar, honey, syrup)
Natural sugars (examples: fresh and dried fruit, fruit juice)
Refined starches (examples: white bread, pastries)
Milk sugar, also known as lactose (examples: cheese, milk, cream).
These diets also eliminate many other foods such as alcohol, foods with mold, food additives, and caffeine. The idea is to eliminate the foods completely for a period of time and then add them back one at a time to see how your body reacts.
What is the connection between fungal overgrowth and IBS?
Yeast overgrowth has been blamed for a number of chronic health conditions with “unexplained clinical symptoms,” including IBS.1,2,6 However, the science that connects the dots between yeast and IBS is limited.6
There is convincing evidence that the gut microbiota plays a role in IBS, especially post-infectious IBS.7 Probiotics are a widely used treatment for IBS, and they are thought to help restore balance to the gut environment. Yet, there are no studies that prove—or disprove—the theory that Candida causes IBS in some patients.6
A position statement from the American Academy of Allergy and Immunology states that the idea that people are oversensitive to Candida is speculative and unproven.3 The authors raise concerns that long-term treatment with anti-fungal medications could lead to fungal resistance and rare side effects.
Does the anti-fungal diet work for IBS?
There are very few studies of anti-fungal diets. None of them prove the diet treats IBS. One study of 28 people showed that eating refined starches did not increase Candida in the mouth or intestine.6,8
Another study include people with “unexplained symptom complex,” who were treated with a combination of an antifungal medication and low-sugar diet.6 Only 9 of the 120 people in this study had been diagnosed with IBS. For the people with IBS, the prescription antifungal was linked with a 35 percent improvement in symptoms. In comparison, the IBS patients who got a placebo only had a 9 percent improvement in symptoms. The low sugar diet was linked with improvement in symptoms for people with and without IBS. The most improvement was seen in non-gastrointestinal symptoms.
Many of the foods eliminated in anti-fungal diets are common trigger foods for IBS. If you avoid eating fruits, sugary sweeteners, starchy vegetables, and dairy to prevent yeast overgrowth, your diet also will be low in FODMAPS. FODMAPs are poorly absorbed sugars and starches that are linked to many IBS symptoms. One difference between the FODMAP diet and anti-fungal diets is that the FODMAP diet allows more foods.
A challenge for people with IBS is that many of the vegetables allowed in anti-fungal diets are high-gas vegetables, such as broccoli, Brussels sprouts, cabbage, celery, cucumbers, and onions. Avoiding high-gas food is one recommendation for managing gas and bloating.
Is the anti-fungal diet healthy?
On the one hand, anti-fungal diets are high in nutrient-dense vegetables and low in processed foods. On the other hand, very restrictive diets are hard to follow and they can lead to nutrient deficiencies in the long-term. If dairy is your usual source of calcium, you will need to plan on including enough calcium-rich vegetables. For vegetarians, protein choices are limited in anti-fungal diets.
Hyman M. Is hidden fungus making you ill? The Huffington Post. 7/24/10. Accessed 8/4/16 at: http://www.huffingtonpost.com/dr-mark-hyman/yeast-infection-symptoms_b_657354.html.
Schulze J, Sonnenborn U. Yeasts in the gut: from commensals to infectious agents. Dtsch Arztebl Int. 2009;106:837-842.
Candidiasis hypersensitivity syndrome. Executive Committee of the American Academy of Allergy and Immunology. J Allergy Clin Immunol. 1986;78:271-273.
The Candida Diet. Accessed 8/4/16 at: http://www.thecandidadiet.com/
The Yeast Connection. Accessed 8/4/16 at: http://www.yeastconnection.com/default.htm
Santelmann H, Howard JM. Yeast metabolic products, yeast antigens and yeasts as possible triggers for irritable bowel syndrome. Eur J Gastroenterol Hepatol. 2005;17:21-26.
Salonen A, de Vos WM, Palva A. Gastrointestinal microbiota in irritable bowel syndrome: present state and perspectives. Microbiology. 2010 Nov;156(Pt 11):3205-3215.
Weig M, Werner E, Frosch M, Kasper H. Limited effect of refined carbohydrate dietary supplementation on colonization of the gastrointestinal tract of healthy subjects by Candida albicans. Am J Clin Nutr. 1999;69:1170-1173.