For the quick answer to your question: no and sometimes.
While not all molds are bad for you to eat, many are, and unless you want to whip out
a microscope and meticulously identify the mold present on your food (note: there are
300,000 known types and counting), as a general rule it’s better to avoid moldy foods.
Not all molds that are bad for you will cause apparent symptoms right away either.
For instance, many molds produce Aflatoxin which is a substance that will up your chances
of getting cancer and may cause a variety of other health problems for you, though not
necessarily right away.
That being said, sometimes it is OK to cut off the mold and eat what’s underneath.
As to when it’s OK to eat moldy foods and when it’s not, it depends on the food item.
With respect to bread and cheese, it’s important to understand that the visible mold you see
on the surface of bread and cheese also sends root threads down into the food.
In molds that are bad for you, these threads often have poisonous substances in and around
these ‘roots’.
With hard cheeses, the mold has trouble penetrating deeply into the cheese.
As such, you can cut an inch of cheese off of each side and discard the moldy slices
and it should be safe to eat (note: just scraping the visible mold off isn’t good enough,
you must cut deeply in, to make sure you’re getting rid of the runners).
Thus, hard or semi-hard cheeses like Cheddar, Colby, Gorgonzola, Gruyere, Parmesan, Romano,
Stilton, and Swiss, among others, are completely fine to cut the moldy part away and eat what’s
underneath.
Soft cheese like Brie, Camembert, Cottage cheese, Cream cheese, Neufchatel, or Ricotta
you should throw out if you notice mold on them.
In addition to that, any shredded or crumbled cheese, regardless of type, should always
be discarded if you discover mold.
All that being said, some cheese is made with mold, such as the aforementioned Brie, Roquefort,
and Camembert.
Obviously the mold that the cheese is made with is safe to eat.
But if you notice other mold growing on the cheese, cut it off or throw it out depending
on whether it’s hard or soft cheese.
Now with breads, you should always throw away the bread when you discover mold on it.
Even though in a solid loaf you could easily cut off a couple inches of the moldy part,
unfortunately because bread is so porous, the mold has no trouble spreading its runner
threads throughout the bread’s innards, unlike with hard cheeses.
In the case of sliced bread, you also usually should throw away the whole loaf.
Mold spreads amazingly fast, so if you see one spot of mold, it’s likely that the other
bread in a package also has mold on it, even if you can’t see it yet.
The same goes for shredded cheese, one spot of mold visible likely means that it has also
spread to the entire package of shredded cheese.
So, as a general rule, if the food item is hard (hard cheese, hard fruits and vegetables,
etc.) and has mold, it’s usually alright to cut off some of the food item and eat what’s
underneath, particularly when there is a low moisture content in the food item.
Soft fruits and vegetables, like strawberries, oranges (note: the outer rind is easily penetrated
by mold), green beans, etc. should be thrown out when mold is discovered.
For semi-soft food items or hard items with high moisture content, as a general rule when
these items turn moldy, “when in doubt, throw it out”.
Pro Tip: when cutting moldy cheese away, be particularly carefully to keep the knife blade
from touching the mold spots.
This will reduce the likelihood of spreading the mold to the uncontaminated innards.
Once you’re done cutting the moldy cheese away, putting it in a new package will also
help significantly towards keeping it mold free for longer.
Also, never sniff mold, this can result in respiratory problems.