If you look in your cupboard and start reading nutrition labels on your favorite box of granola or your gummy vitamins, there's a good chance you'll notice a popular ingredient: fruit concentrate.

"Fruit concentrate is not really something I thought about," says Wendy Rae Little via Twitter. She is a blogger living in Belle Vernon, Pa. But once Little started going through her pantry and began noticing fruit concentrate listed as an ingredient, it influenced her purchases. For example, Little buys only orange juice that says "not from fruit concentrate" on the label, because it "sounds fresher." But in other products — like the baby food pouches she gives her granddaughter — Little intuitively considers fruit concentrate a healthy ingredient, more-or-less interchangeable with fruit.

So, what is fruit concentrate, exactly? And should consumers avoid it or seek it out?

Fruit concentrate is "fruit with the water removed," says Caroline West Passerrello, a registered dietitian nutritionist and a spokesperson for the Academy of Nutrition and Dietetics. "It retains the sugar and calories, but it loses the volume, fiber and vitamin C."

Fruit concentrate was developed in large part because lower volume makes products cheaper to ship and store. But to make it, one has to remove the pulp and skin from fruits, depriving consumers of the fiber they would get from an old-fashioned apple, according to Passerrello. Plus, making fruit concentrate requires heating fruit to remove the water, a process that destroys heat-sensitive vitamin C.

When fiber and vitamin C get squeezed out of fruit, so does much of its nutrition. Fiber helps slow digestion, so consuming fruit concentrate spikes blood sugar more quickly than munching traditional fruit. Vitamin C is a type of antioxidant that helps with a basketful of bodily functions, so losing vitamin C slashes benefits ranging from body tissue formation to immune system response.

In other words, people should view fruit concentrate as an added sugar, similar to high-fructose corn syrup, according to Vasanti Malik, a research scientist in the Department of Nutrition at the Harvard T.H. Chan School of Public Health. Even if the fruit concentrate is combined with fiber in the final product, Malik says its inclusion should still raise eyebrows.

"We're seeing children's cereals that are whole grain, but then have a lot of added sugar" in the form of fruit concentrate, says Malik. "Although it's better than eating spoons of sugar, it's not great" because the sugar is included in such large amounts.

She also says fruit juices and processed smoothies can contain a lot of added sugar, with little fiber benefit. Malik notes that fruit juices in general, even those without fruit concentrate, are naturally full of sugars and calories, making them less nutritious than some might believe.

One way to avoid that added sugar is to take matters into your own hands and make your food from scratch. For granola, Passerrello advises using dried fruit and just a little maple syrup. But she admits the time-consuming DIY method "isn't always realistic."

She proposes another option for the time-crunched grocery shopper: "If you pick up three granola bars at the store, pick the bar where fruit concentrate [or other added sugar] is last on the ingredient list." The last item on the ingredient list is usually the smallest in amount. "Hopefully you can find one without it," she adds.

And Passerrello says the Food and Drug Administration's updates to nutrition labels will soon make it easier for consumers like Little and the rest of us to figure out how to think about fruit concentrate. Sugar from fruit concentrate, she says, will be called out as an "added sugar."

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