Galactosemia is a rare genetic metabolic disorder, occurring in approximately 1:10000 infants. This is typically picked up on newborn screening in the USA, although some of the variants that are mild forms of galactosemia may not be identified early. These infants cannot metabolize galactose, which is in lactose, the main sugar in breastmilk. Build-up of galactose is termed galactosemia, and is associated with feeding problems, failure to thrive, low blood sugar, liver damage, bleeding, jaundice, shock from infection, and brain damage. These infants need a lactose free formula as soon as it is diagnosed¹.

Breastfeeding with other inherited metabolic disorders, such as maple syrup urine disease and other disorders of amino acid or protein metabolism, is not contraindicated. Infants need to be followed closely by a metabolic specialist, and may need nutritional supplementation while breastfeeding².