Best before dates act like a 'hard cutoff', but the reality is the risk of eating food is typically an exponential increasing from the time it was made. It just starts from a very low value.
Just a single gone-off meal can kill you, so you can't try all that many times and hope to find the limit of survivability.
Many things will keep for months or years after the best before date. One of the most ridiculous ones are eggs which will normally last months - yet have a mandated best before of 28 days.
"Use by" are the ones to take note of. Those are the perishables like milk or meat where the bacteria count matters. These are the ones that have been arrived at by food safety testing.
Even those are designed to be pessimistic enough to cope with the fact that a huge proportion of fridges are running several degrees higher than recommended, and people will leave things on the side for a few hours etc
They were there from the start, but the USE BY date takes into account common pathogens and how they multiply in correct household storage.
About 3000 people die from food poisoning every year in the US.
The parent is probably talking about food that's not more than a few days past expiry, since they worked in a grocery store. The risk from not following a mostly-arbitrary date is not much higher if properly stored than say, eating improperly-stored food.
A student died eating pasta stored at room temperature for five days: https://www.dailymail.co.uk/news/article-6638715/20-year-old...
Things might have turned out differently if it was stored in the fridge.
Worst case it'll make you sick..
A regular meal can kill you too.
It's one of the reasons why hot countries often have spicy, highly flavored foods. Before refrigeration people could use poor quality meat for longer by covering up the taste, and it didn't kill them because lots of spices have anti-bacterial qualities.
But yeah, it can be masked.
Not having decide if something has gone bad reduces decisions I have to make :)
You will be able to smell if food is rotting. USE BY dates aren't just about rotting though, they take into account commonly found bacteria in different food, and correct storage.
You won't be able to smell most types of food poisoning bacteria, and the risk of poisoning goes up after the use by date.
https://www.food.gov.uk/safety-hygiene/best-before-and-use-b...
For example, flies circling round meat would make most people instinctively think twice before eating it. In most environments, they will appear within a few hours of the creature dying. In your fridge, the flies won't hatch, taking away a vital signal marking the age of the food.
Personally I use use by dates (I don't really check best before dates) as a shopping tool, so I buy thing that will last the time required, then rely on my senses.
Canned goods have best before dates on for heavens sake, I'd happily eat a 10 year old can of X, assuming it's none bulging.
Cooked rice is the only thing I'm aware of that can kill you after cooking, whilst still appearing ok.
USE BY is product safety information. The risk increases after the use by date.
BEST BEFORE is product quality information. There's not much risk but the taste and nutrition will degrade over time.
Although it would be nice to have the time to check best befores and use bys of everything I put in my trolley, in practice its basically meat and milk, purely to check that they will last until I want to use them.