[logan troy]

Hello I have a 5 month old son and we buy 9 month to 24 month milk for him does this hurt the child at all

[DoulaLC]

hello i have a 5 month old son and we buy 9 month to 24 month milk for him does this hurt the child at all

The reason for the follow-on or hungry baby milks is that they are designed to try and meet the nutritional needs for babies that age. Whether they are really necessary is debatable and partly depends on what else baby may be eating at that point.
The calories, proteins, fats, and nutrients change for the older baby and this may inturn cause a younger baby's digestive system to have to work harder. They may not always digest the milk as they should and therefore may not be absorbing the nutrients as they should.

Will they drink it?. sure they will and you may not notice any change, but their digestive system might. There is nothing magical that happens at a specific age, but we know their systems are still maturing into the first year and much of this maturation doesn't occur until the second half. This is partly why solids are not recommended too early as well. Babies may gladly have them, but their digestive system is having to work harder.
An age range is given because this is when most babies will likely do just fine. Some may do well sooner, and some may benefit from waiting even longer, you just can't tell which way your child may fall.

Is it an issue at 5 months?. probably not, but it's not necessary at 5 months, and if you don't have to use it, might be better to wait awhile longer.