Most babies in the U.S. are introduced to complementary foods too early -- before the age of six months -- according to a new study.

This study highlights the importance of introducing babies to solid foods at the right time to ensure they benefit as much as possible from the nutrients found in breast milk or infant formula.

After following 1,482 U.S. infants age six to 36 months, researchers found that more than half of the babies (54.6 per cent) were given food or drinks other than breast milk or infant formula (e.g., cow's milk, juice, sugar water, baby food) too early -- before the age of six months recommended by the WHO.

The study found that babies who were never breastfed or who were breastfed for less than four months were the most likely to be introduced to complementary foods too early.

According to the results, only a third (32.5 per cent) of babies were introduced to solid food at around six months, in line with recommendations. Complementary foods were given given to 16.3% of babies before four months, 38.3 per cent of babies at four months and 12.9 per cent of infants at seven months or older.

Introducing complementary foods too soon isn't recommended, but starting them too late can also have consequences, such as micronutrient deficiency, allergies and poorer diets later in life, the researchers warn.

The study is published in the Journal of the Academy of Nutrition and Dietetics.