The ketogenic diet is not recommended during breastfeeding, because safety has not been clearly established. Breastfeeding itself can induce ketosis because it increases energy demand, and these demands can be met by an increased carbohydrate intake, gluconeogenesis (where the liver uses stored glycogen to release glucose into the blood), or the use of fatty acids as an energy source.[1]
Lactation ketoacidosis occurs in breastfeeding mothers who are severely undereating, although it is quite uncommon in humans. The resulting acidosis in the body can be severe and usually requires treatment in a hospital. The added ketosis produced by a ketogenic diet can cause lactation ketoacidosis, and there has been a case report of severe lactation ketoacidosis in a breastfeeding mother on a ketogenic diet.[2]