- Ah, the egg aisle, the land of endless choices and confusing labels.

Cage free, free range, organic, it's enough to scramble your brain.

I'm Sheril Krishenbaum, and on this eggsciting episode of "Serving Up Science," we're cracking the code of all those terms on egg cartons.

Let's begin with the post popular option, conventional eggs.

In the U.S., this means that an egg comes from chickens residing in what are called battery cages.

They house more than 70% of hens, and typically hold four to seven birds each, and are only 40 centimeters tall.

Regulations do vary by state, but for reference, that's smaller than an 8.5 x 11 piece of paper.

While technically the size can vary, that's the minimum standard from United Egg Producers, which is the U.S. agricultural cooperative representing American egg production.

They also estimate that about 15% of chickens are raised in cages that don't even meet these standards.

So battery cages can be pretty cramped quarters for chickens, which some animal rights activists consider inhumane.

Okay, now why do poultry farmers use these tiny cages?

There are actually some benefits.

Tight space is said to decrease social friction, and limit exposure to predators and disease.

And there's also efficiency.

Battery cages feature a sloped wire floor that makes it easy for eggs to roll down to a conveyor belt at the start of their journey to grocery store shelves.

But what about alternatives to these cramped quarters for hens?

Enter cage free and free range eggs.

Cage-free eggs, a term regulated by the U.S. Department of Agriculture or USDA, come from hens that are allowed to roam inside the poultry house, so not in cages.

But this does not necessarily mean they are allowed to go outside.

When it comes to free range eggs, another USDA term, these come from hens that have some sort of access to the outside world, even if it's a tiny, fenced in yard.

The USDA requires that both free range and cage-free eggs come from hens that must be allowed to exhibit natural behaviors, and include enrichment such as scratch areas, perches and nests.

Hens must have access to liter, protection from predators, and be able to move in a barn in a manner that promotes bird welfare.

And then there are organic eggs, which means that the chickens had some outdoor access, and were also cage free.

These birds received organic feed so their diets didn't contain any animal byproducts like most synthetic fertilizers and pesticides.

That may sound like a luxurious lifestyle, but there are some downsides to being an organic bird too.

Organic hens aren't directly fed synthetic amino acids that many poultry scientists say can improve their overall health.

Last but not least, we've got the pasture-raised eggs.

If you see that carton boasting pasture-raised along with stamps like certified humane and animal welfare approved, each of these birds had at least 108 square feet of outdoor space to roam and explore.

These chickens also had the opportunity to forage for larva.

Some research shows that pasture raising hens leads to eggs with healthier omega-3 fats, and more vitamin E than eggs from caged hens.

Still, a pasture raised egg isn't necessarily any healthier an a conventional egg.

The agricultural scientists consulted while researching this episode explain that there's no consistent difference in nutritional quality of eggs raised in any of the different systems I've described.

We also can't exactly generalize the living conditions for pasture raised hens to mean one thing or another.

You see, factors like geography, season, temperature, soil and more all influence the bird's diet and health.

So, just as we see with so many topics we cover in this series, food science is nuanced, and it's all about context.

So what should you choose next time you're at the supermarket?

There's not really a right answer.

It all depends on your priorities, and how much you're comfortable spending.

(cash register dings) Fortunately, whether conventional, cage free, free range, organic or pasture raised, they can all still make a great fried egg.

So I just hold it up and then drop, is that?

- [Crew] Yep.

- Bon appetite.

(egg clinks) Oh, that one did not...

I should have just dropped it.

I was a little too excited.

- [Crew] You threw it down.

- I threw it in the pan.

Bon appetite.

You're gonna have so many good outtakes.

Bon appetite.

It worked.

(upbeat music)