His mother needs to feed him food.

Food at the end sounds redundant to me.

And it makes it sound as if there were alternative substances other than food that he might be fed, and the sentence is specifying food as opposed to those alternatives.

The first thing I thought to myself when I read the longer sentence was "As opposed to what? Feeding him shoe polish?"

I'd say the shorter sentence is correct. Unless a sentence specifies otherwise, the phrase "feeding someone" should automatically be presumed to be talking about feeding them something edible.

Further details are only necessary if the type of food is being specified, or if someone is being forced to eat something other than food.