Yes, maltodextrins are safe during breastfeeding and any other time (especially related to exercise) unless you’re borderline diabetic and then you should limit daily amounts because of a potential blood sugar spike. Maltodextrins are fast acting sugars, which is why it’s a popular ingredient in athletic formulas, as in before, during and after exercise supplements, because you want it to digest quick to reach the muscles/glycogen fast. Make sure your daily diet also contains fibrous carbs such as grains, fruits and vegetables as well.