Love marshmallows on your sweet potato casserole? Here's what marshmallows are made of.

Even Dolly Parton is on board with adding marshmallows to a sweet potato casserole on Thanksgiving.

The country music icon, 78, debuted a new cookbook, titled "Good Lookin' Cookin'," with sister Rachel Parton George earlier this fall. They share recipes for every month of the year, and what would a November chapter be without Southern cooking for Thanksgiving?

The Parton sisters' sweet potato casserole recipe calls for sweet potatoes, butter, light brown sugar, vanilla extract, salt, ground cinnamon, raw pecans and mini marshmallows. (You can check out the full recipe via Real Simple.)

“The sweet potato is a vegetable that’s perfect for the fall – the color and the flavor always make us think of harvest time,” the sisters write in the book on the sweet potato casserole page. “Rachel likes to cover her casserole with marshmallows. You have to – it’s just one of those things. But she also adds some pecans on top – we love the taste they add, making this extra special.”

How do those mini marshmallows on top impact the nutrition of the overall dish? Here's what nutrition experts want you to know ahead of your Thanksgiving plans.

What are marshmallows made of?

Marshmallows are believed to date back to the ancient Egyptians, who made the treat out of the mallow plant, typically grown in marshes. (See what they did there?)

Today, marshmallows are comprised mainly of corn syrup, cornstarch, sugar, water and gelatin, per the National Confectioners Association. (That gelatin means most marshmallows aren't vegan, by the way –gelatin is comprised of animal protein.)

A cup of mini marshmallows usually contains about 159 calories, with less than a gram of protein, hardly any fiber and very little to zero of any essential vitamin or mineral, according to the U.S. Department of Agriculture's food database. That cup also contains 28.8 grams of sugar, nearly the entire amount of daily added sugar recommended by the American Heart Association.

So it's not exactly a nutritional powerhouse. But as long as you're not eating marshmallows every single day for breakfast, lunch and dinner, health experts say you can still leave a place for them on the menu.

"While marshmallows are mostly sugar and lack significant nutrients, they can still have a place in your holiday meals," Washington, D.C.-based registered dietitian Caroline Thomason, CDCES, tells USA TODAY.

Recipe: Easy sweet potato casserole will have everyone asking for seconds

Are marshmallows healthy to eat?

We're not going to stand here and tell you marshmallows are a health food. But that also doesn't mean you have to leave them off your plate this Thanksgiving.

Thomason recommends building your plate with "nourishing foods that you enjoy," including vegetables, whole grains and protein, but also allowing yourself to savor your favorite holiday treats.

More: Why 'overindulging' at your Thanksgiving dinner isn't a big deal

"When enjoyed in moderation and as part of a balanced meal, having a higher sugar food like marshmallows isn’t likely to affect your health long-term. Eating for joy is a huge part of the holidays – so if you love them, enjoy them as part of a balanced plate and move on without the guilt," Thomason says. "Slowing down and savoring each bite can also help you tune into the fullness cues that can help prevent overeating, too. ... Focus on balance and listening to your body’s hunger and cravings on the holiday."

This article originally appeared on USA TODAY: What are marshmallows made of?