Q:

how much vegetables or how many vegetables?

I know that vegetable is a count noun, but Which one of the quantifiers do we use with vegetables.
How much vegetables do our bodies need?
How many vegetables do our bodies need?

A:

From Longman Dictionary of Contemporary English:

Grammar
  Vegetable is a countable noun, not an uncountable noun:
      They grew their own vegetables (NOT their own vegetable).

Using the word in plural form basically refers to all the various types of vegetables; i. e. carrots, tomatoes, parsley, etc. 
However, talking about the quantity, it'll depend on the type of the vegetable you're talking about and the general context. 
You'll ask a quantity-related question about vegetables if you 're buying some; then if you're buying it by weight, that'll be for example two kilos of vegetables, so the question would be "How much vegetables ...?" 
Although, that'll apply to the countries with good climate for growing vegetable, where in the other parts of the world, specially in the West, where shops don't usually sell vegetables per weight, they'll come in packs or pots. So the question would be "how many packs/pots of vegetable...?" 

