You can say that alimento is all that stuff that is suitable to make a meal with, whilst food (comida) is the prepared stuff you eat.
for those who are familiar with German it's like Lebensmittel and Essen.
If you look at the definitions you will see they can be used as synonyms, but alimento is more related with nutrition and comida with the act of ingesting food.
You can even say Esa comida no alimenta nada, meaning that the nutritional value is nearly 0
The hints are not really a cheat sheet that you can look at and do a word for word translation. They are just hints. There is often no word for word translation possible. Words may have to be dropped, added, the whole sentence rearranged. It could be an idiomatic expression where few or none of the words are directly translated. In this particular case we are experts in English (assuming you're a native speaker like myself) and just have to know that "foods" sounds odd here.