comida = food
alimento = nourishment
alimento, like nourishment, has a broader definition.
alimento pra alma = nourishment for the soul
Plantas, fungos e bactérias também precisam de alimento = Plants, fungi and bacteria also need nourishment
I hope you find a clearer explanation on it in some discussion. Briefly, alimento is more formal and not very used frequently...
Well, maybe in Portuguese is the same, but in Spanish we tend to use "comida" for "our" food. "Alimento" for animal's food.. But still they mean the same food. "Nuestra comida/Nossa comida".. "Alimento para animales/Alimento para animais".. However, the verb "alimentar" (to feed) is used for both humans and animals.. Hope it helps and i hope somebody corrects me if i'm wrong lol
My english is very poor, but I'll try.
Alimento: apple Comida: apple pie
Alimento is any ingrediend, fruit, vegetables, etc. Comida is something prepared to eat. I hope you can understand what I mean.
But in portuguese we rarely use alimento.