Many parents look forward to the day they can introduce solids to their little one—opening the door to those adorable messy mealtime photos and enjoyable family dinners.

But don’t rush into it, warn researchers from the Centers for Disease Control: According to a new study conducted by the CDC, 54% of American parents introduce some type of solid food to their infants before the age of six months.

“Introducing babies to complementary foods too early can cause them to miss out on important nutrients that come from breast milk and infant formula,” says Chloe M. Barrera, MPH, CDC lead investigator.

The sweet spot: Starting solids when babies are six months.

For the study published this week in the Journal of the Academy of Nutrition and Dietetics, CDC researchers analyzed reports on 1,482 children from the 2009-2014 National Health and Nutrition Examination Survey. They found 16.3% of parents start their babies on solids such as rice cereal before infants are 4 months. Another 38.3% start when the infants are 4 or 5 months old.

Only one-third start at the six-month mark, which is what’s recommended by the American Academy of Pediatrics (AAP)—with another 12.9% holding off until the babies are 7 months or older, which poses its own set of risks.

“Introducing them to complementary foods too late has been associated with micronutrient deficiencies, allergies, and poorer diets later in life,” explains Barrera.

Waiting until babies are 6 months old—but not much later—is an update on traditional recommendations, which once had parents start solids around the age of 3 months.

“Efforts to support caregivers, families, and healthcare providers may be needed to ensure that U.S. children are achieving recommendations on the timing of food introduction,” says Barrera, who suggests the upcoming Dietary Guidelines for Americans include recommendations for children younger than 2 years old to achieve better consistency nationwide.

The AAP formally recommends exclusively breastfeeding until babies are 6 months old. Between six months and one year, solid foods should be seen as a complement—not replacement—to breast milk or formula.

The AAP does note parents should speak with their own pediatrician for advice specific to their babies.