A side of leafy vegetables is a delicious and healthy accompaniment for every meal, which explains why pre-packaged veggies like lettuce are very popular on the market.

Very little else can beat the convenience of being able to pop into a nearby supermarket to buy a small portion of bagged lettuce to enjoy with your quick lunch. But, there's also nothing more frustrating than discovering that the lettuce isn't fresh.

Thus, the never-ending search for foolproof ways to detect freshness of bagged lettuce. Recently, a Reddit post went viral for its claim of finding the ultimate trick for this — buying the flattest bag of lettuce you can find!

According to the post from user, @Bradliss, a flatter bag of lettuce signals its freshness because when greens are originally packaged, the air is sucked. As the lettuce ages, however, it emits gas which makes the bag puffy.

But, that has been debunked as it isn't good enough to determine freshness of bagged lettuce. According to experts, lettuce does give off gas after it's bagged, but it's also put into a plastic bag designed to modify the atmosphere within it.

That packaging is termed, "Modified Atmosphere Packaging," which is used to accommodate the gasses given off by the lettuce, and also ensure that they don't start the browning or spoilage process. In other words, this bag "breathes."

So, it turns out that the truly authentic way to be sure a bag of lettuce is fresh before buying is by checking the "Best By" date.