Take a look at these two sentences:
I prefer to eat organic fruits and vegetables.
If you’d like to try something exotic to eat, there are special sections for foreign foods.
*Fruit and food are usually used in the singular form.
In English, there are countable (count) nouns and uncountable (non-count) nouns.
Countable nouns = things that you can count:
1 plant, 2 plants, 2 plants
1 tooth, 2 teeth, 3 teeth
Uncountable nouns = things that you cannot count, or nouns that represent a group:
*They have NO plural form.
Usually food is an uncountable noun. You can’t count one food, two foods, etc.
Do you have any food to eat?
There was so much food at our Thanksgiving dinner!
Food is also an uncountable noun when we talk about different kinds of food:
When I said foreign foods I used foods to describe the food from different countries:
foreign foods = Chinese food, Italian food, Indian food, Japanese food, German food, etc.
*In this case, it’s OK to use foods in the plural form.
Usually fruit is an uncountable noun. In English, we usually count fruit by saying 1 piece of fruit, 2 pieces of fruit, a bowl of fruit, etc.
It is OK to use fruits when you are talking about many different kinds of fruit:
You can find bananas, grapes and other fruits in the produce section.
Make sure to eat five servings of fruits and vegetables daily.
Other uncountable nouns that can be countable:
BBC Learning English: peoples, persons