This is what happens if you accidentally eat mould

You’re enjoying your breakfast when you notice that your banana muffin seems to have grown a patch of fuzzy green dots. You have already taken a bite or two. Now, you wonder, what happens if you eat mould?

First, don’t panic. Most healthy people can accidentally eat some mould here and there and feel totally fine. A lot depends on the type of food (after all, some foods, like gorgonzola, and other blue cheeses are made with mould cultures) and on your underlying health status, like your immune system. Here’s a brief explanation of mouldy foods you can eat – and which ones to avoid.

Moulds are microscopic fungi that can grow on wood, paper, carpet, food and building materials, such as insulation. All moulds need water or moisture to grow. Wherever there is moisture and oxygen, mould can grow.

There are many species of fungi, with some estimates suggesting 300,000 or more, according to the United States Department of Agriculture (USDA). This is why the mould that pops up on your breakfast muffin may look different than the furry layer that grows on your luncheon meats, explains gastroenterologist Elena Ivanina. Unlike bacteria, moulds grow in structures that contain many cells, and you don’t need a microscope to see them. In general, moulds consist of root threads that run deep into food, a stalk that rises above the food, and spores at the end of the stalks. Spores give mould its variety of colours and also help transport it from item to item.

“If you pick up a dandelion and blow on it, the seeds disperse in the air, and that’s how mould spores travel from place to place, contaminate products and cause spoilage,” says Robert Gravani, professor and director of the National Good Agricultural Practices Program.

“Moulds are nature’s decomposers. If you have a piece of fruit with mould, eventually that fruit will be decomposed,” says Gravani. “Moulds are very efficient in what they do.” In fact, some can be very beneficial. The life-saving antibiotic penicillin is made from Penicillium mould, Dr Ivanina notes.

Mould thrives in warm, humid environments, but that doesn’t mean it can’t also form and grow in your refrigerator. Moulds are pretty smart, too, and tolerate preservatives such as salt and sugar better than most other food invaders. “They are pretty hearty critters,” Gravani says.

Some people are allergic to mould, says Dr Ivanina. This is usually mould in the environment as opposed to food, but for these people, exposure to mould can cause vomiting, diarrhoea or headaches. If your doctor suspects a mould allergy is to blame, you will likely be referred for testing, she says.

Hidden patches of mould can lurk in all different areas of your home and may make you sick.

“If you have an underlying health condition that affects your immune system, exposure to mould can be dangerous,” Dr Ivanina says. “You may have a much worse reaction to eating mould than someone else because you don’t have a healthy immune system to fight that reaction.”

A few moulds produce mycotoxins, or poisonous substances that can make you very sick. For example, moulds produced by the Aspergillus species can cause aflatoxicosis, a life-threatening form of acute poisoning with the potential to cause liver damage.

This type of mould tends to lurk in cereals: oil seeds such as soybean, peanut, sunflower, and cotton seeds; spices; and tree nuts. These mycotoxins have been linked to cancer in animals and can cause liver cancer in humans. “Some are highly toxic, which can get you really sick or cause cancer,” says Gravani.

When it comes to food, it can be tempting to cut away mould and eat it anyway, given the high price tags of certain products, but it’s usually not worth it, Gravani says.

Besides the risk of illness, mouldy food doesn’t taste great, he says. Most moulds on soft foods will taste like soil or dust. If it looks like mould, it likely is mould, so don’t smell it, as according to the USDA, sniffing it can cause respiratory issues.

When in doubt, throw it out, Dr Ivanina says. This is a good motto for mouldy foods, but there are some more specific guidelines to keep in mind too.

Here’s how to tell if these 10 foods have expired.

If your mouldy food can’t be found on the link, download a free app that tells you what to do if you find mould on 600 types of food. The FoodKeeper app was developed by the USDA’s Food Safety and Inspection Service with Cornell University and the Food Marketing Institute. “It offers rough guidelines to the question, how long can I keep this?’” says Gravani.

There are different rules for cheese depending on its texture.

Hard cheese

Hard cheeses (not to be mistaken with those that have mould as part of the process) can be consumed if you cut off at least 2cm around and below the mould. Make sure to keep the knife away from the mould to avoid spreading it. Still, Gravani adds, “If the hard cheese is heavily encrusted with mould, I would probably discard it.”

Soft cheese

If you see mould on soft cheese such as cottage, cream cheese or all types of crumbled, shredded and sliced cheeses, throw it out. These may be contaminated below the surface and can also have bacteria growing along with the mould.

Some cheeses are made with mould including Roquefort, blue, Gorgonzola, Stilton, Brie, and Camembert. If they contain moulds that are not a part of the manufacturing process, these cheeses can be dangerous.

Like cheese, there are different rules for fruits and vegetables based on the texture.

Soft produce

Discard soft fruit and veggies like cucumbers, peaches and tomatoes if you spy any mould. Many of these may also be contaminated under the surface, says Dr Ivanina.

What you see isn’t all that you get with moulds. “Root” threads from the mould tend to run deep, especially in foods that show heavy mould growth.

Firm produce

You can keep these if you cut out all the mould. This is due to the low moisture content as seen with firm fruit and veggies like cabbage, capsicums and carrots. With these types of foods, mould can’t penetrate them easily.

The rule of thumb for mouldy luncheon meat, bacon and hot dogs is to discard as they may be contaminated under the surface and also harbour bacteria, Dr Ivanina says.

Hard salami and dry-cured country hams

You can keep these meats if you scrub off all of the surface mould. The USDA points out that it is normal for these shelf-stable products to grow surface mould.

Cooked casseroles and leftover meat and poultry

Get rid of these if you see mould as there is a good chance it runs deep and it may travel with bacteria. It’s also a smart idea to use or get rid of leftovers within three or four days.

Cooked grains and pasta

Like other leftovers, if you see mould on cooked grains or pasta, toss it. There is likely mould under the surface too and there’s also a risk of bacteria.

Yogurt and sour cream

If you see mould, get rid of yogurt and sour cream immediately. Mould is likely growing beneath the surface too, and there’s a good chance that the mould is travelling with bacteria.

Jam

These should be thrown away if you see any mould. These foods could be producing a mycotoxin if they develop mould, which is why microbiologists warn never to scoop out the mould and use the remains.

Bread and baked goods

Get rid of mouldy bread and baked goods, says Dr Ivanina. “Mould can spread really fast on soft things like bread and muffins.”

Peanut butter, legumes and nuts

Discard these because foods processed without preservatives are at high risk for mould.