We’ve all been there: discovering fuzzy growth on our favorite foods. From a lone, moldy strawberry to a loaf of bread with green spots, finding mold on food can be unsettling. Beyond the initial disgust, concerns about potential health consequences often arise. What exactly what happens if you eat moldy food? How much mold is too much? And what about foods like blue cheese that are intentionally moldy?
Here’s a breakdown of why mold grows on food, the potential effects of consuming it, and practical tips for keeping your food mold-free.
Understanding Mold
Molds are microscopic fungi, as explained by Josephine Wee, Ph.D., an assistant professor of food science at Penn State University. These fungi are related to mushrooms and yeast. Therefore, while all molds are fungi, not all fungi are molds.
Mold is a ubiquitous part of our environment, thriving wherever moisture and oxygen are present, according to the U.S. Environmental Protection Agency.
With tens of thousands of species, molds spread by releasing tiny cells called spores. “The spores are everywhere; they are on our skin, in the air that we breathe, on our foods,” Wee explains.
Outdoors, mold plays a crucial role in decomposing organic matter like fallen leaves. Indoors, however, it can spoil food and grow on damp surfaces, making it undesirable.
“Molds grow in the right conditions… They like higher humidity and warmer temperatures,” Wee notes. This explains why refrigeration slows down mold growth on food.
Randy Worobo, Ph.D., professor of food microbiology at Cornell University, adds that molds, like all living microorganisms, require oxygen to grow. This is why cheeses and other moisture-rich foods are often vacuum-packed, as mold can quickly develop after exposure to air.
“One of the unique characteristics of molds is that they’re really good at growing on just about anything… They’re scavengers,” says Worobo. Even in the refrigerator, mold can eventually form on foods over time. Anyone who has forgotten about leftovers knows this all too well.
The Spectrum of Mold: From Good to Harmful
When discussing molds, it’s essential to recognize that some are more harmful than others. As Wee puts it, “There’s the good, the bad, and the ugly,” with the “ugly” referring to toxic molds.
“Good” molds are intentionally used in the production of certain cheeses. For example, Penicillium roqueforti is used to create blue cheeses like Roquefort, Gorgonzola, and Stilton. Penicillium camemberti is used in Camembert and Brie cheeses, which have a characteristic white mold surface, Worobo explains.
The USDA confirms that the mold found in and on these cheeses is safe for consumption. “These are intentionally added to the milk cultures,” Wee clarifies, reassuring blue cheese enthusiasts.
“Bad” mold refers to the mold that grows on food due to spoilage, says Wee. Food mold appears in a variety of colors and textures. On bread, it may appear as green or black spots, Wee explains, while berries often develop a white, cotton-like fuzz, and citrus fruits can have a green or gray dusty appearance.
Mold can also be red, pink, or orange, and its color can change throughout its life cycle, says Wee.
What Happens If You Eat Mold? The Risks
In most cases, accidentally ingesting food with mold will not cause any harm, according to experts. “When you ingest the mold, the acids in your stomach, as well as the digestive enzymes, will break the cells down,” says Worobo. Generally, healthy individuals won’t get sick from eating a few bites of moldy food.
“For the general population, it’s not a big deal,” Worobo adds.
However, those with weakened immune systems are at higher risk, as the mold could potentially colonize and cause fungal infections. These individuals should be especially cautious and avoid mold altogether.
Moreover, certain types of mold – the “ugly” ones – can produce toxic substances known as mycotoxins under specific conditions, says Wee. These toxins can cause illness in anyone and pose significant health risks.
The World Health Organization (WHO) reports that exposure to toxic molds can lead to adverse health effects in both the short and long term. The most dangerous mycotoxins are aflatoxins, which the USDA identifies as potentially carcinogenic to humans.
Since it’s impossible to determine the type of mold or its toxicity simply by looking at it, it’s best to avoid eating moldy foods whenever possible.
How Much Mold is Too Much?
The quantity of mold consumed is also a factor. While the average person is unlikely to get sick from ingesting small amounts, larger quantities can cause nausea or stomach upset, experts say.
Wee explains that people are naturally inclined to avoid spoiled food. “You’re not going to eat a slice of moldy bread because it does not taste good and it’s not appealing to the eye. It’s a sensory issue,” she says, noting that moldy food may have an unpleasant odor or an earthy, dirt-like flavor.
Most people will likely spit the food out or discard it before consuming much of it, Wee adds.
Any amount or type of mold can cause issues for people with mold allergies, experts warn. This often happens through inhalation, but eating mold can also trigger a reaction. “Even though there are no toxins that are present, there are people who cannot eat even small amounts (of moldy food) because of the spores,” Wee explains.
According to the Mayo Clinic, symptoms of an allergic reaction to mold can include sneezing, runny nose, or itchy throat.
The WHO notes that ingesting large doses of certain mycotoxins can lead to acute poisoning or life-threatening liver damage. Fortunately, this is relatively rare.
Cutting Around Mold: Is It Safe?
The mold you see on the surface of food may actually penetrate much deeper, experts warn. Wee likens it to the roots of a tree growing underground.
The USDA explains that mold consists of thread-like roots that invade the food, a stalk that rises above the food (often invisible to the naked eye), and spores that form at the end of the stalks. The spores are what you see growing on the food.
Therefore, cutting out or around mold may not eliminate it entirely, experts caution. In fact, Worobo points out that slicing a knife through a moldy spot can spread the spores to other parts of the food.
Moldy, spoiled foods may also contain bacteria that can cause illness, even if they are not visible. To be safe, discard any food that shows signs of mold or has come into contact with other moldy food, Wee advises.
When to See a Doctor
If you’ve accidentally eaten moldy food, try not to panic. Unless you have a compromised immune system or have consumed a large quantity of mold, you will likely be fine. However, it’s important to monitor for any symptoms, experts advise. If you feel well, you can continue as normal.
Seek medical attention if you develop severe gastrointestinal symptoms or signs of an allergic reaction, such as shortness of breath, elevated temperature, vomiting, or wheezing, according to the Cleveland Clinic.
If you have any concerns or questions about eating mold, it’s always best to consult with your healthcare provider.
Preventing Mold Growth on Food
Here are some steps you can take to minimize your exposure to mold spores and prevent mold from growing on your food, based on recommendations from experts and the USDA:
- Discard any food that shows signs of mold growth.
- Avoid sniffing moldy food to prevent inhaling spores.
- Thoroughly clean any surfaces and containers that have come into contact with moldy food.
- Refrigerate all perishable foods at 40 degrees Fahrenheit (4 degrees Celsius) or lower.
- Store and refrigerate cooked food within two hours of serving.
- Cover foods while serving to prevent exposure to airborne spores.
- Consume or discard leftovers within three to four days.
- Carefully inspect all food for signs of mold before purchasing.
