The fraud in your cupboard

I'm a big fan of the Mediterranean Diet, and not just because it's proven to keep waistlines down, prevent disease, and extend lives.

It's also downright delicious.

One of the big reasons this diet is both healthy and tasty is the liberal use of heart-friendly olive oil -- especially the high-quality extra virgin olive oil loaded with antioxidant and anti-inflammatory properties.

Just one problem: The expensive stuff in your own cupboard -- the stuff that says "extra virgin" right on the label -- might be extra pricey... but it's not even remotely virgin.

In 2010, researchers from the University of California-Davis tested 14 major brands of "extra virgin" olive oil and found that two-thirds were actually blended with cheaper canola, seed and/or nut oils.

Last year, the same team tested 134 olive oil samples from eight producers, and found that 73 percent flunked the taste and smell tests established by the International Olive Council.

If that's what passes for purity, then olive oil is about as pure as the driven snow... after it's been visited by the neighborhood dog.

And it doesn't end there.

In 2007, U.S. Marshals broke up a counterfeiting ring that was passing off cheap soybean oil as pricey EVOO. In 2008, Italian police made 60 arrests and shut down nearly 100 farms and processing plants over olive oil fraud.

And last year in Spain, two businessmen were given jail sentences for selling "extra virgin olive oil" that was up to 80 percent sunflower oil.

It's scandal after scandal after scandal... over something as seemingly innocuous as olive oil.

So how can you make sure you get what you pay for and enjoy both the great taste and unparalleled benefits of real EVOO? Not by the color -- true EVOO can actually vary anywhere from green to gold. And not by taste, since the fakes can often taste just like the real thing.

You have to do your homework.

For starters, you can take a look at the brands that passed the UC-Davis test: Corto Olive, California Olive Ranch, Kirkland Organic, Lucero (Ascolano) and McEvoy Ranch Organic all proved to be the real deal, while many of the most widely used brands flunked out.

You can also look for International Olive Oil Council certification as well as PDO (protected designation of origin) and PGI (protected geographical indication), but none of these things alone are guarantees.

For that, you'll have to visit the farm... or press the olive oil yourself.