Moldy food — you probably shouldn't eat it.
Eating a lot of mold all at once could make you really, really sick.
In contrast, eating just a little bit of mold probably wouldn't do very much to you at first,
unless you're allergic.
But eating small amounts of mold repeatedly over many years, scientists think that could
cause serious health problems, from cancer to kidney and liver disease.
But how likely is that?
How likely are you to give yourself cancer or destroy your liver by eating a little bit
of moldy bread or something every single day?
Well, the problem is nobody really knows how likely that is, for reasons we're going to
get to.
But from what I can see, the majority opinion among food safety experts is, don't risk it.
If the bread is moldy, throw it out.
The part of the mold you can clearly see is really just the tip of the iceberg.
I'll show you under the microscope.
With foods that are more solid, like firm cheeses, the interior is less likely to be
affected.
So you really can cut away the mold and eat the rest.
Indeed, some cheeses have mold in them by design.
Not all mold is gross and dangerous.
Why is some of it delicious and benign?
And what even is mold?
Well molds are fungi, like mushrooms.
Fungi don't move around or have nervous systems, so they're kind of like plants.
But they don't photosynthesize, they don't make their own food.
Fungi eat existing organic matter.
And in that, they're kind of like animals.
Molds are fungi, but they're not mushrooms.
"Molds are kind of like the smaller, distant cousins of mushrooms.
But in a lot of molecular ways, they're quite similar."
Dr. Megan Biango-Daniels is a mycologist focusing on food spoilage.
She's done work on bread mold, and cheese and fruit mold, all that kind of stuff.
And she says that if she were going to draw a comparison from the plant kingdom, you could
say that mushrooms are kind of like trees.
Trees have roots, trunks, leaves, lots of different parts.
Tissue specialization.
Mushrooms are like that too.
They have their equivalent of roots underground, then they send up the fruiting body, which
is the actual mushroom.
It has a stem, a cap, gills underneath to drop its spores and reproduce.
Different parts made up of different kinds of tissues.
Mold is to the mushroom as maybe green algae is to the tree in the plant kingdom, assuming
that you're talking about the kind of algae that scientists still consider to be plants.
There is debate there.
But, anyway.
If this algae is a plant, it has very little in the way of distinct parts.
There's no stem, no leaves.
This algae is mostly threads made up of the same basic kind of cell, all strung together.
Molds are the fungal equivalent of that.
"Molds have sort of microscopic structures.
If you're thinking about Penicillia, they have these tiny little spherical structures
that form, and then they have chains of spores coming off of them.
But they don't really have the same sort of tissue specialization."
For the most part, molds are just threads of fungal cells.
The individual threads are called hyphae, and the broader network of threads all connected
together is known as the mycelium.
You can see mycelia inside this moldy bread with your naked eye.
But with this very weak microscope, I can get you a little bit closer.
It's kind of hard to tell the mycelium apart from the gluten strands in the bread.
But the really thin, the white spiderweb looking stuff, that is mycelium.
That is mold.
Mushrooms grow from mycelia too.
But with molds, the mycelia is pretty much all there is to the organism.
The threads start out from an individual spore, and then they grow looking for food.
Like other fungi, they release enzymes into the environment to dissolve nutrients.
They digest your food.
Then they suck those nutrients back up, and use them to keep growing.
And when it's time for them to reproduce, they might send up a teeny tiny little microscopic
spore-bearing structure.
But that's not really what you're seeing on the surface of that moldy bread.
That blue-green stuff on the surface is the spores themselves.
The part of the mold that isn't light-colored threads is generally the spores.
They're on the surface so that a gust of wind — or maybe an animal passing by, such as
yourself — will carry them away to some other wet and nutrient-rich environment where
they can start growing into hyphae and the circle of life, et cetera, et cetera.
The spores are naturally kind of loose on the surface, so they kick up into the air
really easily.
And that's one way that they make people sick.
People will breathe in the spores, and if your immune system overreacts to them, you
have an allergic reaction that can make you sick — asthma, that happens with some people.
But that would depend on your genetics and those of the mold.
Which mold species is it?
On bread, it could be so many things.
"But I think when you think about the usual suspects, you're thinking about blue-green
molds, which are maybe Penicillia or Cladosporiums.
And then you're also thinking about those black and gray molds that you see, which might
be Rhizopus or some other Mucorales.
Maybe rarely you'll see an Aspergillus, I think."
And there's even more possibilities.
Molds are incredibly diverse, their spores are incredibly resilient, and they can just
survive dormant in the environment for a really long time just waiting for you to bring a
fresh loaf into the house.
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Anyway, the diversity of mold species out there makes it very difficult to answer the
basic question that we're all asking, which is, how actually dangerous is the mold we
find on our food?
Is it going to kill us, immediately or over time?
Unfortunately, it just depends.
But yeah, it can be dangerous, not just if you're allergic.
There are toxins made by the molds.
"In addition to all the enzymes that molds are producing in order to feed and kind of
live their lives, they're also producing this host of secondary metabolites.
So these are compounds that you might associate with that wet basement smell, that sort of
very moldy, dank smell.
It's actually a chemical signal that molds are releasing into the environment as they
grow."
A secondary metabolite is a chemical compound made by an organism that is not essential
for its basic growth and reproduction.
An example that we make would be pheromones, the chemicals that we make to smell good to
potential mates.
Those are secondary metabolites of ours.
Fungi have those too, for all kinds of different purposes.
And when those secondary metabolites happen to be toxic to us, we call them mycotoxins.
"We think they're involved in sort of communication with other molds, or defenses against other
microbes in the environment.
But we really don't know a lot about why they're produced, when they're produced.
And they're definitely bad.
They can cause acute toxicity in humans and other lab rats that we've studied."
And those mycotoxins are not just going to be found in the part of the fungus you can
see, which in this case is the spores on the surface.
Most of the organism is the mycelia spreading freely through that soft, open structure inside
the bread, where you could easily not see it because it resembles gluten strands.
By the time you have visible spores on the bread surface, there's probably tons of mycelia
running through the loaf.
"I have no reason to think that eating the white part of the mold as opposed to the green
part of the mold would be any better.
I think if anything, that kind of hidden, mycelia is probably where you'll see a lot
of the sort of chemicals being made by the molds that might give your food a weird texture,
a weird flavor.
It really is the main body of molds."
Furthermore, it's possible that the mycotoxin itself can migrate in the food, beyond the
body of the mold.
That's a topic of ongoing research, as in this recent paper out of France.
Internal spread of the fungus and/or its toxins — that's probably much more likely in foods
that are soft or wet, which is why you see recommendations like these from the US Department
of Agriculture.
Bread, yogurt, soft cheeses, soft fruits and vegetables — if they're moldy, just throw
them away.
With firm foods, it might be different.
Carrots, firm cheese, dry-cured meats — with those, you can probably cut away the moldy
part and maybe the adjoining inch or so, and you're probably safe.
But what happens if you don't, right?
We've all had the experience of eating something, and then you look down and realize one minute
too late that, oh, that was moldy.
Well, if it doesn't make you immediately sick, if you don't start vomiting, or go to paralysis
or some kind of crazy stuff immediately, well that means it either wasn't very toxic, or
you didn't eat enough of it to make you acutely sick.
So, count your blessings and move on with your life.
But chronic exposure to small amounts of mycotoxins over time — scientists have linked that
with all kinds of health problems.
Mycotoxins can be immunosuppressive, so they make you more susceptible to other diseases.
Mycotoxins can damage your DNA, which could mean cancer.
And mycotoxins can damage the organs that filter the stuff that you eat and drink — so,
your liver, kidneys, and spleen — again, acutely with big doses or chronically with
small doses over time.
How much of the world's liver cancer is caused by chronic exposure to mycotoxins?
Nobody really knows.
I mean, there are studies, people trying to figure this out, but nobody really knows.
Because you're exposed to so many different things over the course of your life that could
cause these problems.
And it's really hard for scientists to untangle all of those, and figure out what caused what
in who.
There's a lot of concern about people in developing countries who get most of their nutrition
from one or two staple grains.
So they might be getting the same mycotoxin over, and over, and over again.
And lots of developing countries are in hot and humid climates that are conducive to fungal
growth, and they aren't always able to keep their grain in the most sanitary conditions.
There's also concerns about occupational exposure to mycotoxins, like you see in mill workers.
They're breathing it in all day.
But when you're talking about normal First-Worlders like most of us, there are scientists who
are concerned that we might actually be a little over-cautious about food mold.
And that could be bad too.
"When I look at a piece of bread that has a lot of mold on it, I think what a waste.
I think about the sort of environment that we're living in today, which is so sort of
food-stressed in a number of ways because of conflict and climate change.
To produce that bread, to get it to your table, it takes so much work.
And then to have you be beat to the table by mold."
So that's why other scientists are working to figure out how much those toxins migrate
through the food as the mold grows.
And other scientists are trying to figure out exactly how dangerous the toxins are.
But why isn't this dangerous?
Lots of cheeses are intentionally inoculated with mold.
The molds break down the fats in the cheese and create a lot of delicious flavor molecules.
"Well, cheese is a really interesting kind of, I think, exception to a lot of what we
know about secondary metabolites and molds.
Because blue cheese, the mold that you have on brie, all of those molds have been very
kind of intentionally cultivated by humans.
And in a way, they've been domesticated by us.
So we've selected them for favorable flavors, favorable appearances.
And there's almost now a very clear number of strains, which are used kind of over and
over for cheese producing, different varieties of cheese specifically.
And we know a lot about how they're different from their very close wild relatives.
And they actually have down regulation in these secondary metabolites, which lead to
off-flavors and potential mycotoxins."
And even then, certain people actually do have bad reactions to the molds intentionally
put into cheeses.
Life is risks.
Life is making choices.
But one way that you can minimize your risk when it comes to food mold is to keep your
susceptible foods wrapped up really, really tightly.
The spores are floating around in the air, and then once they land in your food, the
mold needs air to grow.
So keep things sealed away from air, and it's going to last longer.
But as long as there are nutrients to be had, and as long as the food isn't too acidic or
whatever, mold will happen, eventually.
Life finds a way.
Eat your food before something else does.