The baby was brought in six days ago to a hospital in Pisa before being transferred to the Meyer children’s hospital in Florence, La Stampa reported.
Blood tests revealed that the baby was severely malnourished and the hospital reported the parents to police.
Investigators in Pisa must now determine whether the baby’s malnourishment is connected to the parents’ vegan diet and, importantly, what kind of milk the baby was fed.
They must also establish if the child was ever seen by a paediatrician and if they knew about the parents’ diet.
The parents, who are in their early thirties, could face charges for mistreating their child.
According to La Stampa, the baby is not in danger but their condition requires “serious attention”.
In addition to being vegetarian, those following a vegan diet do not use any animal products or by-products such as eggs, dairy products and honey.
In a statement, an association for Italian vegans ‘Live vegan project’ said:
“Babies and children of vegans and non-vegans need fundamental nutrients to grow. While not entering into the specific case, if the parents did not pay attention to the diet of their child, it is not because they are vegan, but simply because they were, perhaps, guilty of being superficial.”
This isn't the first time parents have been investigated for their dietary habits in Italy. In May an Italian court ordered a vegetarian mother to cook meat for her son at least once a week after the boy's father complained that his son wasn't being given a proper diet.