Yeast

1. What conditions has Yeast been studied for?

• Selenium deficiency / low selenium status: Selenium-enriched foods and selenium-enriched yeast biomass are discussed as strategies to address widespread selenium deficiency.

• Hashimoto’s thyroiditis (autoimmune thyroiditis): A randomized controlled study tested selenious yeast tablets for effects on thyroid antibodies and thyroid function.

• Gastrointestinal (GI) infections and GI symptoms: Saccharomyces boulardii is described as the best-characterized probiotic yeast; clinical trials suggest it can alleviate symptoms of GI tract infections “to some extent.”

• Dyslipidaemia (high cholesterol): A review of functional foods/natural health products notes red yeast rice has “good evidence” for biochemical lipid-lowering effects.

• Acute kidney injury (AKI) and renal tubular disorders linked to a red yeast rice supplement: Case series describes AKI with renal tubular acidosis and Fanconi syndrome after consuming a specific product (“Beni Koji Choleste Help”).

• Oral/dental diseases (oral pathogens, dental caries): A dentistry-focused review discusses probiotics (including yeast) as a strategy to inhibit oral pathogens and influence plaque biofilms (general probiotic concept; not yeast-specific trial evidence in the provided text).

• Food technology outcomes (dough rheology/gluten structure): Selenium-enriched yeast was studied for effects on dough viscoelasticity and gluten depolymerization (not a clinical condition, but a studied application).

• Animal GI health (young ruminants, weaning stress/diarrhea risk): Yeast culture supplementation was reviewed for improving gut microecology and immunity in young ruminants (preclinical/veterinary context).

• Astaxanthin-related health areas: “Red yeast” (Phaffia rhodozyma) is listed as a source organism for astaxanthin; the abstract reviews many potential therapeutic areas for astaxanthin (cardiovascular disease, cancer, diabetes, neurodegenerative and immune disorders), but this is not direct evidence that yeast itself treats these conditions.

2. Does it work in treating those conditions? Summarize the evidence.

• Hashimoto’s thyroiditis: In a prospective randomized-controlled study (Se-treated n=43 vs control n=47), selenious yeast tablet for 6 months was associated with:

  • Decreased TPOAb and TGAb (thyroid autoantibodies) vs control.

  • Decreased TSH vs control; subgroup analysis suggested subclinical HT may benefit more for TSH reduction.

  • Biologic correlates: increased selenium, GPx3, and SePP1, and increased proportion of activated Tregs and Helios-expressing Treg subsets—supporting an antioxidant/immune-regulatory mechanism.

  Limitations: Single study described; clinical endpoints beyond labs (symptoms, long-term outcomes) are not provided in the abstract.

• GI infections / GI symptoms (S. boulardii): The review states clinical trials indicate it can alleviate symptoms from GI tract infections to some extent, but emphasizes that further trials are needed to define full therapeutic potential.

  Limitations: The abstract does not specify which infections, effect sizes, or trial quality.

• Dyslipidaemia (red yeast rice): A review of functional foods reports that red yeast rice is among products with good evidence for a biochemical effect on plasma lipid levels. It also notes that none of these products reduce lipids to the same extent as statins and calls for larger, high-quality RCTs with cardiovascular endpoints.

  Limitations: Evidence is summarized at a review level; cardiovascular outcome data are not established in the abstract.

• Selenium deficiency: The selenium overview argues that selenium is essential and that deficiency is widespread; it proposes selenium-enriched food or yeast biomass as supplementation approaches and notes organic selenium forms (e.g., selenomethionine/selenocysteine) are more easily absorbed than inorganic forms. However, this is a rationale statement rather than direct clinical trial evidence in the abstract.

• Oral/dental conditions: The dentistry abstract supports the general concept that probiotics can alter plaque ecology and inhibit oral pathogens, but it does not provide yeast-specific clinical efficacy data.

• Animal GI health (ruminants): The ruminant review describes yeast culture as alleviating weaning-stress-related GI damage and supporting microbiota and mucosal immunity. This supports biological plausibility but is not direct evidence for human treatment.

3. What health benefits does it have?

• Micronutrient delivery (selenium-enriched yeast): The selenium overview notes selenium is a cofactor for enzymes such as glutathione peroxidase and thioredoxin reductase, and emphasizes selenium’s role in protection against oxidative stress. It also states organic selenium forms (as found in foods/yeast) are more readily absorbed than inorganic forms.

• Potential immune modulation in autoimmune thyroiditis: In Hashimoto’s thyroiditis, selenious yeast supplementation was associated with increased antioxidant markers (GPx3, SePP1) and increased activated regulatory T cells, alongside reductions in thyroid autoantibodies and TSH.

• Probiotic/biotherapeutic potential (S. boulardii and other yeasts): The S. boulardii review highlights phenotypic traits suited for the gut (e.g., acid and heat tolerance) and notes clinical trial evidence of symptom alleviation in GI infections to some extent.

• Lipid-lowering potential (red yeast rice): The dyslipidaemia review lists red yeast rice among natural products with good evidence for improving lipid biomarkers (biochemical effect on plasma lipids).

• Bioactive components in yeast culture (preclinical/veterinary): Yeast culture contains components such as β-glucan and mannan and is described as stimulating mucosal immunity and supporting intestinal epithelial and microbial growth in young ruminants.

• As a production platform for bioactives: “Red yeast” (Phaffia rhodozyma) is identified as a producer of astaxanthin, a compound reviewed as having antioxidant and anti-inflammatory activities and broad therapeutic potential; however, this is evidence about astaxanthin, not necessarily about consuming yeast itself.

4. Does it have any downsides or side effects?

• Serious adverse events reported with a red yeast rice supplement: A case series links “Beni Koji Choleste Help” (red yeast rice supplement) to acute kidney injury with renal tubular acidosis and Fanconi syndrome, with biopsy evidence of tubular injury. Discontinuation and prednisolone improved kidney function in reported cases. The abstract also notes 76 possibly related deaths and 492 hospitalizations reported in Japan.

  Interpretation limits: This is linked to a specific commercial product and does not establish that all red yeast rice products or yeast-derived supplements carry the same risk; it does highlight the potential for severe harm and the importance of product quality/safety monitoring.

• Potential downsides of selenium-enriched yeast depend on dose/status: The selenium overview emphasizes deficiency concerns, but does not discuss toxicity. The provided abstracts do not quantify adverse effects from selenium yeast in humans; nonetheless, selenium is a trace element with a known narrow therapeutic window in general (not detailed in the abstracts).

• Food processing/functional effects (not a health side effect, but relevant): Selenium-enriched yeast slowed gas production and reduced dough viscoelasticity; metabolomics suggested inhibited yeast energy metabolism and changes that contributed to gluten depolymerization and softer dough. This is a technological downside for baking performance rather than a clinical safety issue.

• Probiotic yeast safety: The S. boulardii abstract does not describe adverse events; it mainly notes that more trials are needed to define therapeutic potential.

5. Is it beneficial or harmful for any genetic variations (pharmacogenomics)?

The provided abstracts do not report pharmacogenomic findings (i.e., specific human genetic variants that predict benefit or harm) for yeast-based interventions such as S. boulardii, selenium-enriched yeast, or red yeast rice.

• Hashimoto’s thyroiditis selenium-yeast RCT: Immune cell subset changes (e.g., activated Tregs, Helios expression) were measured, but these are immunophenotypes, not inherited genetic variants.

• Red yeast rice adverse events: The AKI/Fanconi syndrome report does not identify genetic susceptibility factors.

Conclusion: Based on these abstracts alone, there is insufficient evidence to say yeast is beneficial or harmful for specific genetic subgroups; this remains an evidence gap.

References

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