Fiber-fortified soy milk. Cereal enriched with probiotics. Omega-3-fortified juice. You’ve likely seen these labels and more popping up on kids foods throughout the grocery store. It’s not empty hype; when part of a balanced diet, nutritious add-ins are a simple way to ensure your child is well nourished.

“It’s always best to get your nutrients from whole foods,” says Ellie Krieger, RD, author of So Easy: Luscious, Healthy Recipes for Every Day of the Week (Wiley, 2009), and host of Food Network’s Healthy Appetite. “That said, there are circumstances where kids need supplemental nutrients. If they don’t eat calcium-rich foods, for example, calcium-fortified juice is a great choice.” Boosting foods with nutrients is nothing new; bread and cereals have long been enriched with B vitamins to replace nutrients lost during processing, and since the 1930s vitamin D has been added to milk to enhance calcium absorption. But recently, the “functional foods” approach (adding large amounts of nutrients to foods that don’t naturally contain them) has skyrocketed: In 2008, sales of kids functional foods totaled more than $7.7 billion and accounted for 76 percent of all the healthy kids products sold, according to Nutrition Business Journal.

If you do buy fortified foods, stay away from gussied-up junk fare, like diet soda with added vitamins and minerals or sugary granola bars with extra fiber. Also, keep track of how much of a nutrient your child is taking in. “If your child eats calcium-fortified cereal and calcium-fortified juice for breakfast, with calcium-fortified snack bars, plus milk and cheese, he or she may be getting too much,” says Krieger.

Which nutrients are worth looking for in kids foods, and how much does your child need? Here’s what you should know about these supercharged ingredients.

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