What is the omnivore's dilemma?

Basically, the omnivore's dilemma is "what should we have
for dinner."  Since human beings are omnivores, they can eat whatever they want. 
However, all the things that people might eat have implications both for the human
beings themselves and for the planet on which we live.  Having to take into account all
these implications of what we eat creates the omnivore's
dilemma.

The point of this book is to explore some of the
implications of our food choices.  Pollan uses the book to look at what we eat (for
example, the fact that we eat so many things that are dependent on corn) and to discuss
the ramifications of those choices.  He looks at ways in which these choices affect our
own health and he looks at the way they affect global trends such dependence on
oil.

In short, then, the omnivore's dilemma is that
omnivores must face that their food choices have major
consequences.