Antiyeast therapy includes diets that restrict intake of sugar and yeast as well as supplements and drugs to eliminate yeast from the body.
Candida albicans is a form of yeast and is known to cause human infections. In works published from 1978 to 1981, C. Orian Truss was the first to propose the idea that the natural yeasts in the gastrointestinal tract can cause a variety of symptoms (Edwards 1988). In 1983, William Crook popularized this idea with his book, The Yeast Connection, in which he coined the term “Candida syndrome” to explain a host of psychological and neurological syndromes, including learning disabilities. He offered anecdotes as evidence for this syndrome, notably an account of “Candida drunken syndrome” that involved a boy with autism who was said to improve after antiyeast interventions. The popularity of antiyeast therapies for the treatment of autism increased after Shaw et al. (1995) reported abnormal metabolites in the urine of two brothers with autism.
Rationale or Underlying Theory
Current antiyeast therapy was developed by Shaw et al. (1995) based on a report of abnormally high levels of metabolites in the urine of two siblings with autism, compared to typically developing children. These metabolites included citramalic acid, a citric acid analog, tartaric acid, and a compound assumed to be arabinose. From their case report, Shaw et al. made three assumptions: (1) The metabolites are produced by an overgrowth of a fungus or fermenting yeast such as Candida albicans. (2) The overgrowth of fungus or yeast in individuals with autism occurs in the gastrointestinal system rather than the urinary tract. (3) The growth interferes with normal metabolism and produces symptoms of autism. None of these hypotheses have been confirmed by independent investigators in peer-reviewed studies, and some are considered biologically implausible (Lord 2003).
Goals and Objectives
The goal of antiyeast therapy is to rid the body of yeast. William Shaw (2008) recommends probiotics, antiyeast diet, and antifungal products as antiyeast therapies.
Shaw (2008) offers tests for yeast overgrowth through his Great Plains Laboratory and recommends probiotics, antiyeast diet, and antifungal products as antiyeast therapies. Probiotics can be found in yogurt or purchased as supplements from pharmacies or health food stores. An antiyeast diet is a low-sugar diet with the simple mantra: “If it’s sweet, don’t eat”. Nonprescription antifungal supplements include garlic, oregano, caprylic acid, MCT oil, colloidal silver (although Shaw acknowledges that this may be dangerous), lactoferrin, and biotin. Prescription antifungal drugs that are considered safe because they are poorly absorbed from the intestines include nystatin and amphotericin B. Other prescription antifungals which Shaw does not consider to be as safe are Sporanox (itraconazole) and Lamisil (terbinafine). The use of any prescription drug should be closely supervised by a board-certified physician.
Dr. Shaw reports that combining diet and antifungals “double[s] the effectiveness of diet alone in eliminating yeast overgrowth.” However, he does not cite any evidence for a link between autism and yeast and does not report on the validity of his lab tests. Furthermore, he concedes that no “formal assessments” are available to address the effects of the diet and antifungals on the core symptoms of autism (2008). At this time, no clinical trials have been performed, and only anecdotal evidence supports the application of antiyeast diets or medications. Levy and Hyman (2008) have categorized antifungal therapy as a Grade C treatment for autism, supported only by low-quality evidence. According to a consensus statement from an expert panel of clinicians, antiyeast therapy is not recommended for patients with autism spectrum disorders at this time (Buie et al. 2010).
Antiyeast treatment is intended to reduce autism symptoms and improve adaptive functioning. Therefore, if clinical trials of antiyeast therapy are undertaken, outcome measures should include measures of autism symptoms such as the ADOS and measures of adaptive behavior such as the Vineland. Also, because the mechanism by which the treatment is postulated to work is to reduce intestinal yeast overgrowth, well-validated measures of intestinal yeast should be included.
Qualifications of Treatment Providers
A physician should be contacted before beginning an antiyeast therapy. The use of antifungal medications should have ongoing supervision from a board-certified physician.