Yeasts and Molds: Understanding the Health Implications

Caitlin Beale, MS, RDN

Yeasts and Molds: Fungi are present everywhere in the natural world. The CDC estimates that millions of fungi species exist, but only a few hundred are known to cause health problems in susceptible people (1).

This article examines our exposure to molds and yeasts, potentially adverse health outcomes, and how you can minimize exposure.

What are yeasts and molds?

To understand the effect of yeasts and molds on our health, we need to know what they are.

• Yeasts: Yeast are a group of single-celled fungus found both naturally in humans as well as used in food production to make fermented foods such as dough, wine, and beer (2). We have beneficial yeast that lives in our body as part of our microbiome, keeping our gut healthy. We also eat foods that are fermented with yeast, as mentioned above. If the balance of yeast in our body shifts, yeast overgrowth can occur and make us sick (3).
• Molds: Mold is also a fungus found naturally in the environment. Mold grows in moisture-rich environments. The spores of mold move through the air as it reproduces. While we are exposed regularly, mold becomes a problem if it grows in excess in food, supplements, or in our home where breathing in the spores can cause illness (4).

What types of fungi can cause health problems?

While most fungi are harmless, there are several species that can cause specific health problems including:

• Cryptococcosis-neoformans: A kind of fungus that causes illness when breathing it in. Infections are unusual for most people but can make people with compromised immune systems very sick. Cryptococcosis most often affects the lungs and central nervous system (5).
• Aspergillus: A common mold found in both indoor and outdoor environments, aspergillus also rarely causes illness in healthy individuals but instead can make those with weak immune systems ill. Aspergillus causes a variety of illnesses, ranging from allergy symptoms to more severe infections (6).
• Candida Auris: A newer fungus discovered in 2009, Candida Auris is a concern at healthcare facilities such as hospitals and nursing homes. This fungus is easily spreadable between patients or objects. Candida Auris is especially a concern because it can lead to bloodstream infections causing death and can be medication resistant to common antifungals (7).
• Candida is a type of yeast that usually lives on the skin and body but causes infections when it overgrows or enters the bloodstream. Infections can be mild (such as thrush or yeast infections) to severe (known as invasive) (8).
• Mycotoxins: Beyond the spores and yeast overgrowth, certain molds produce a type of toxin called mycotoxins. They can be found in a variety of food (ex: coffee, cereal, and spices) and supplements. Mycotoxins can cause illness in humans – from acute symptoms that mimic food poisoning to more severe conditions like cancer (9).
• Stachybotrys chartarum: This is the mold that people are often referring to when discussing “black mold.” Especially concerning when found in homes, it can grow in humid rich environments when there is water damage or leaks, or flooding (10).

Yeasts and Molds: What are the health risks from exposure to fungus?

Health risks from fungus range from mild to life-threatening. Mild illness can appear as a skin rash. If the fungus infects the lungs, it can cause more significant concerns such as asthma or other breathing problems (11). Those with lowered immune systems such as people with HIV/AIDS, patients with cancer, or those who take medications that lower the immune system are at most risk. Infants, pregnant women, and the elderly are also more at risk.

Fungi can cause or exacerbate many different types of illnesses, including:

• Asthma
• Allergies
• Rashes or skin infections
• Lung disease
• Non-specific symptoms such as headaches, nosebleeds, fatigue, fever, and gastrointestinal issues

What does science say about fungal illness?

It can be challenging for scientists and researchers to identify cause and effect directly to mold growth in buildings.  Homes that have mold often have other contamination issues such as bacteria, chemicals, and dust mites. Currently, there are no agreed-upon validated tests for mold exposure, making it difficult to assess causation (12).

In 2004, the Institute of Medicine published an extensive study on the health effects of mold.

The study concluded that there was enough evidence connecting mold to upper and lower respiratory tract conditions. While non-specific symptoms, as listed above, were not included due to lack of available research and lack of standardized assessments, but not necessarily disproven (13).    However there have been several studies conducted that did conclude a connection between mold and human illness including infections, irritation, and immune dysfunction (14).

There have been several high publicity cases linking mold to more severe illnesses – with mixed outcomes.

The CDC initially reported a possible connection between acute pulmonary hemorrhage and mold exposure in the case of 10 infants in Ohio who lived in homes with significant water damage and high levels of S. chartarum mold (15). However, after an extensive analysis, the CDC later concluded that there was not adequate evidence to prove the connection, but they did note more studies are needed (12). Flood-damaged homes following national disasters also have been a growing source of exposure (16).

Another concern beyond the exposure and illness to molds and yeasts is the issue of medication resistance. Antifungal drugs are used to treat infections caused by fungi, but some have developed resistance to the medication, meaning it no longer works. For people with the rare, but serious invasive infection affecting blood or organs, this is especially dangerous (17).

Yeasts and Molds: Where are we exposed to fungus?

From soil to our skin, yeasts and molds are pervasive in the environment and our bodies. Again, it’s overgrowth that becomes a problem for our health. The most common reasons for fungal exposure occur in the following conditions:

• Buildings and homes. Mold in our home and workplace has become more of a concern in recent years. Modern building practices have focused on high-efficiency homes, which has, in turn, decreased airflow. Proper airflow is necessary to avoid moisture buildup that leads to mold. Air conditioning use may also play a role as fungi may flourish in air conditioning units.

 Experts also believe that indoor water leaks are a common problem. One study examining moisture in many homes, schools, and office buildings found almost 50% of samples had dampness or mold issues, and potentially even higher numbers in tropical settings with more moisture (13).

Mold can also grow anywhere there is moisture in a home, including furniture or front- loading washing machines.

• Contaminated foods and supplements. Certain foodborne molds and yeasts are dangerous to human health because of the mycotoxins. Mycotoxins are not destroyed by heat, so if present can persist through cooking. Further, molds and yeasts can be a problem for our health for those who have sensitivities or allergies. Yeasts and molds are not only present in the foods or supplements but can be a part of the packaging, lids, or production equipment.

A study examining plant-based dietary supplements found the presence of mycotoxins in 96% of the samples tested (18).

Poorly stored grains and cereals such as maize, wheat, barley, oats, and rice in moist conditions are more likely to grow mold. People can also be exposed to mycotoxins through meat or poultry that eat contaminated feed. Mycotoxins are also found in crops grown in the tropics such as cotton, peanuts, and spices (19).

• Hospitals and nursing homes. Fungal infections are a growing problem in healthcare. In a space where people have compromised immune systems and close interactions, the threat of opportunistic yeast and fungal infection can be a risk. A study examining sepsis (a potentially life-threatening response to infection in the body) determined that the number of people who had sepsis as a result of fungal infection increased by 207% from 1979 to 2000 (20).

Yeasts and Molds: How can you avoid exposure to fungus?

While mold and yeasts are ubiquitous in our environment, it’s clear we need to be extra cautious to avoid excess exposure. The CDC does work to monitor outbreaks to improve response and study the trends – specifically with regards to healthcare and known fungal disease (21).

There are steps you can take personally to reduce your exposure. While this is especially important for those with weakened immune systems, mold exposure should be minimized for everyone.

In the home.

If a home has had mold exposure, or if you live somewhere where you are attempting to avoid mold growth, the CDC recommends working to control humidity, fix any water leaks, and ensure proper ventilation in areas that are higher in moisture such as the bathroom, laundry, or kitchen. Using exhaust fans and dryer vents that move moist air outside your house is essential. Avoiding carpet in these areas is also ideal (12).

Avoiding mold may be easier for new home building.

The balance between energy efficiency and proper air circulation is an important consideration.  A holistic approach to limiting moisture out of and around the home is essential. There are mold-resistant products available, including mold-resistant drywall, paint, insulation, and treated wood. Inspecting materials for high levels of moisture content before installation, installing a quality filtration system for your HVAC, and choosing alternatives to carpet flooring can all support a mold-free home (22).

In food or supplements.

For the average person, avoiding mold in food is as simple as making sure the food isn’t spoiled and watching for any growth. However, for those who are sensitive or potentially allergic to mold, certain foods are more likely to cause problems. These are foods that are fermented or aged, including:

• Cheese
• Kombucha
• Beer or wine
• Mushrooms
• Fermented vegetables like sauerkraut or kimchi
• Yogurt or sour cream
• Peanuts (due to mycotoxin content for some sensitive individuals)

Keep in mind that these foods are fine – and health-promoting for many people. It’s only those who are sensitive or allergic that may have a problem.

Supplements should be verified by third party testing such as NSF International or United States Pharmacopeia (USP) that independently test for contaminants including mold. If a supplement has this verification, it will also be regularly assessed and verified as safe.

Yeasts and Molds: The Takeaway

Mold is everywhere, but only certain species can cause health concerns.  You can take steps to protect yourself in your home environment, as well as with food and supplements to reduce your exposure. If you or a loved one have a lowered immune system, make sure you check your home for water damage or moisture exposure.

Fermented foods are a healthy choice for many people, but should be avoided for those with mold or yeast allergies.  Always check your supplements for third-party verification of purity to avoid contamination.

References:

• “About Fungal Diseases.” Centers for Disease Control and Prevention, Centers for Disease Control and Prevention, 13 May 2019, cdc.gov/fungal/about-fungal-diseases.html.
• “Yeast.” Merriam-Webster, Merriam-Webster, merriam-webster.com/dictionary/yeast.
• “What Is Yeast and What Can It Do?” WebMD, WebMD, webmd.com/diet/ss/slideshow-yeast-and-your-body.
• “What Is Mold?” WebMD, WebMD, webmd.com/women/qa/what-is-mold.
• “C. Neoformans Infection.” Centers for Disease Control and Prevention, Centers for Disease Control and Prevention, 27 Aug. 2019, cdc.gov/fungal/diseases/cryptococcosis-neoformans/index.html.
• “Aspergillosis.” Centers for Disease Control and Prevention, Centers for Disease Control and Prevention, 24 Mar. 2020, cdc.gov/fungal/diseases/aspergillosis/index.html.
• “Candida Auris: A Drug-Resistant Germ That Spreads in Healthcare Facilities.” Centers for Disease Control and Prevention, Centers for Disease Control and Prevention, 21 Dec. 2018, cdc.gov/fungal/candida-auris/c-auris-drug-resistant.html.
• “Candidiasis.” Centers for Disease Control and Prevention, Centers for Disease Control and Prevention, 13 Nov. 2019, cdc.gov/fungal/diseases/candidiasis/index.html.
• “Mycotoxins.” World Health Organization, World Health Organization, who.int/news-room/fact-sheets/detail/mycotoxins.
• “Facts about Stachybotrys Chartarum (Aka ‘Black Mold’).” Centers for Disease Control and Prevention, Centers for Disease Control and Prevention, 16 Dec. 2019, cdc.gov/mold/stachy.htm.
• “Fungal Diseases Homepage.” Centers for Disease Control and Prevention, Centers for Disease Control and Prevention, 18 Feb. 2020, cdc.gov/fungal/index.html.
• “CDC – Mold – General Information – Basic Facts.” Centers for Disease Control and Prevention, Centers for Disease Control and Prevention, 16 Dec. 2019, cdc.gov/mold/faqs.htm.
• Weinhold, Bob. “A Spreading Concern: Inhalational Health Effects of Mold.” Environmental Health Perspectives, National Institute of Environmental Health Sciences, June 2007, ncbi.nlm.nih.gov/pmc/articles/PMC1892134/.
• Bush, Robert K. et al. “The Medical Effects of Mold Exposure.”  Journal of Allergy and Clinical Immunology, Volume 117, Issue 2, 326-333. https://www.jacionline.org/article/S0091-6749(05)02591-1/fulltext.
• “Update: Pulmonary Hemorrhage/Hemosiderosis Among Infants — Cleveland, Ohio, 1993-1996.” Centers for Disease Control and Prevention, Centers for Disease Control and Prevention, cdc.gov/mmwr/preview/mmwrhtml/00045680.htm.
• “Mold and Endotoxin Levels in the Aftermath of Hurricane Katrina: A Pilot Project of Homes in New Orleans Undergoing Renovation.” National Institute of Environmental Health Sciences, U.S. Department of Health and Human Services, ehp.niehs.nih.gov/doi/full/10.1289/ehp.9258.
• “Antifungal Resistance.” Centers for Disease Control and Prevention, Centers for Disease Control and Prevention, 17 Mar. 2020, cdc.gov/fungal/antifungal-resistance.html.
• Zdenka, V. et al., “Mycotoxins in Plant-Based Dietary Supplements: Hidden Health Risk for Consumers.” Journal of Agricultural and Food Chemistry, 2015 Volume 63, issue 29, 6633-6643.
• Samuel, et al. “Fungal Mycotoxins in Foods: A Review.” Taylor & Francis, tandfonline.com/doi/full/10.1080/23311932.2016.1213127.
• DJ, Pfaller MA; Diekema. “Epidemiology of Invasive Candidiasis: A Persistent Public Health Problem.” Clinical Microbiology Reviews, U.S. National Library of Medicine, pubmed.ncbi.nlm.nih.gov/17223626/.
• “Mycotic (Fungal) Diseases.” Centers for Disease Control and Prevention, Centers for Disease Control and Prevention, 2 May 2016, cdc.gov/ncezid/dfwed/mycotics/index.html.
• “How to Build a Mold-Resistant Home or Commercial Building.” AWCI, awci.org/media-archives/construction-dimensions/190-how-to-build-a-moldresistant-home-or-commercial-building.