Most food products for babies and toddlers contain too much of this ingredient.

Watch These Nutrients in Your Child's Diet

The transition from infancy to toddlerhood marks a critical developmental period. Your child’s brain is bursting with more than 100 trillion synapses, enabling him to perform increasingly complex tasks—from walking, then running, jumping, and climbing, to listening and eventually speaking. But a balanced range of nutrients is important to help support this rapid progress.

Now that he’s no longer solely reliant on breast milk or formula (which won’t meet all of his nutritional needs at this stage), he’s also starting to take a more active role at mealtime. He’s becoming increasingly adept at feeding himself—and increasingly willful when it comes to asserting his taste preferences. With that in mind, perhaps it’s not surprising that this might be a time when nutrient imbalances could begin to show up.

According to researchers, there are a number of nutrients that parents should be paying close attention to, as they’re the most likely to be consumed in inadequate amounts—either too little or too much. Here’s a look at a few of the nutrients researchers have identified as possible concerns.

Fiber

Who’s at risk? Dietary fiber was low in the vast majority of toddler and preschooler participants in a large study—likely because they weren’t getting the recommended amounts of fruits and vegetables, which are natural sources of fiber. Among toddlers ages 19 to 24 months, about 23 percent ate no vegetables in a given day, and about 33 percent ate no fruit. (Among toddlers ages 15 to 24 months in the study, French fries were the vegetable most often eaten!)

Why is it important? Fiber aids digestion and helps promote satiety, reducing the likelihood of overeating.

What can you do? Make fruits and vegetables part of every meal and snack—especially after your child grows out of the strained food stage and begins eating finger foods. Offer whole grain cereals and breads, as well, which are good sources of fiber.

Iron

Who’s at risk Nine percent of toddlers 12 to 35 months old don’t receive adequate iron. By about 4 to 6 months old, your baby has diminished the iron stores accumulated in the womb, and breast milk doesn’t provide enough to replenish them. Children under 5 who drink more than 32 ounces of cow, goat, or soy milk a day may be at risk of not getting adequate amounts of iron, as the milk may displace other iron-rich foods.

Why is it important? Babies and toddlers need iron to support their healthy growth. It’s essential for healthy cell function and carrying oxygen from the lungs to the brain and throughout the body. Numerous studies have found a direct link between lack of iron and deficits in mental and motor development. But excess iron can be harmful, as well, so be sure to consult your pediatrician before starting your baby on a supplement.

What can you do?Iron-fortified formula can help provide adequate amounts of iron. For children eating solid foods, vitamin C helps the body absorb iron. So in addition to iron-rich meat, iron-fortified cereals, and dark green vegetables, serve vitamin C–rich foods, such as melon, berries, tomatoes, and oranges.

Potassium

Who’s at risk? Early in life, babies absorb potassium from breast milk or formula, but toddlers may not get adequate amounts. Because of this, it is important that their diets include healthy plant sources of potassium.

Why is it important? This important mineral allows for proper cell functioning throughout the body. It plays a role in neural messaging, muscular function (particularly in the heart), and maintenance of healthy blood vessels.

What can you do? Serve more fruits and vegetables, including leafy greens, vine fruits (like melons, tomatoes, cucumbers, and pumpkins), and root vegetables. It may require creativity to incorporate potassium in dishes; try adding zucchini to muffin batter or bake chips from roasted, sliced beets or kale.

Saturated Fat

Who’s at risk? For most children, fat doesn’t need to be restricted during the first two years of life, but after age 2, your toddler should get no more than 30 to 35 percent of his calories from fat (averaged over several days). Three-fourths of preschoolers in a large study consumed more than the recommended level of saturated fat.

Why is it important? Babies and toddlers need healthy fats to help support brain development and growth, support the immune system, and help absorb fat-soluble vitamins. Saturated fat should be limited as it may be associated with risk of heart disease, obesity, and other health problems.

What can you do? Switch to lower fat milk (1 percent or nonfat), reduced-fat cheese, and other low fat or nonfat dairy products as soon as your child’s doctor says it’s OK. Healthy fat choices also include avocado, fish, and foods made with olive, safflower, or canola oils.

Sodium

Who’s at risk? Researchers found that 45 percent of 12- to 23-month-olds and 78 percent of 2- to 4-year-olds exceeded the recommended sodium intake in their diets.

Why is it important? Sodium is important for maintaining the water balance in the body, regulating blood volume, and ensuring proper cell and tissue function. High sodium intakes may be associated with high blood pressure and elevated risk for heart disease and stroke.

What can you do? Check food labels for sodium content. In 2013, Centers for Disease Control researchers evaluated more than 1,000 food products for babies and toddlers, including cereal bars and crackers, and they found that most foods contained too much sodium. Serve fewer processed foods, which are high in sodium. Avoid bacon, hot dogs, and sausage—all high-sodium meats that your toddler doesn’t need—as well as store-bought cookies, chips, and candy.