Apples: There’s More Under That Peel Than You Think
Where I live in New Jersey, September means apple season.
It's the time of year when local orchards begin filling with people picking bags of red, green and golden apples, and farm stands pile them high in baskets. Depending on where you live, your local apple season may begin a little earlier or later - but for many of us, apples are one of the unmistakable signs that fall is on its way.
And suddenly apple cider, applesauce and apple pies start sounding like a very good idea again.
But an apple is more than a sweet, crunchy fall fruit.
Hidden in that familiar peel are fiber, pigments and an assortment of natural plant compounds — including one with a rather unusual name: quercetin.
Meet Quercetin
Quercetin is a phytochemical belonging to a large family of plant compounds called flavonoids.
Plants don't make quercetin because it's good for people. They make it for themselves.
In plants, quercetin and related flavonoids can help protect tissues from ultraviolet light and other environmental stresses. They are part of the plant's own chemical defense system.
And apples happen to be one of the foods in which we can find quercetin.
But there's a catch.
It isn't spread evenly throughout the apple.
Don't Forget the Peel
If you peel an apple before eating it, you're removing more than its color.
A considerable amount of an apple's quercetin is concentrated in its peel.
That makes sense when you think about what quercetin does for the plant. The peel is the apple's outer surface — the part exposed to sunlight and the surrounding environment.
Apple peel also contains other phytochemicals and fiber, so when the peel is edible and appropriate to eat, leaving it on gives you parts of the apple you would otherwise throw away.
That doesn't mean a peeled apple suddenly becomes unhealthy. It still provides nutrients, fiber and carbohydrates.
It simply means the peel has something extra to offer.
Red, Green or Yellow?
Walk through an orchard and you'll quickly discover that “apple colored” isn't really a color.
Apples can be deep red, rosy pink, bright green, golden yellow or striped with several colors at once.
Those colors come from different plant pigments.
Red apple skins contain anthocyanins, the same broad family of pigments responsible for many red, purple and blue colors in plants.
Green apples retain more visible chlorophyll in their skin.
Yellow and golden apples reveal more carotenoid pigments as chlorophyll declines during ripening.
And underneath those visible differences, the apples contain other compounds that may have little or nothing to do with the color we see.
Quercetin is one of them.
Do All Apples Have the Same Amount?
No - and this is where apples get even more interesting.
The amount of quercetin and other phytochemicals in an apple can vary with the variety, growing conditions, sunlight exposure, ripeness and even where on the fruit the sample is taken.
An apple growing in plenty of sunlight may not develop exactly the same phytochemical profile as one growing under different conditions.
Plants respond to their surroundings.
That means two apples don't have to be chemically identical just because they're both apples.
Food is a lot more complicated than a nutrition label can show.
What Happens When We Eat Quercetin?
Quercetin has attracted considerable scientific interest because researchers have studied its antioxidant and anti-inflammatory activities and its possible effects on a number of processes in the human body.
One area of interest is the body's response to allergens.
Quercetin has been studied for its ability to influence cells and chemical messengers involved in allergic and inflammatory responses. That doesn't mean eating an apple is a treatment for allergies, and research involving isolated or supplemental quercetin isn't the same thing as simply eating quercetin-containing foods.
But it does give scientists another reason to be interested in a compound that plants were making long before humans ever gave it a name.
An Apple Is a Little Package of Plant Chemistry
It's easy to look at an apple and see lunch.
A plant sees something very different.
That apple developed from a flower. Its tissues grew around seeds. Pigments changed as it matured. Its skin formed a protective outer covering. And throughout that process, the tree produced an enormous assortment of natural compounds that helped it grow, reproduce and respond to its environment.
We eventually came along and started giving some of those compounds names.
One of them was quercetin.
So the next time you pick up an apple this fall, take a look at the peel before taking that first bite.
There's a lot more going on under - and in - that peel than you might think.
