Olive oil has a deservedly good reputation as a healthful oil, rich in monounsaturated fatty acids (specifically oleic acid) and compounds called polyphenols. The health benefits of the Mediterranean diet, notably improved cardiovascular health, are attributed in part to the inclusion of less-processed, high-polyphenol extra virgin olive oil–the highest grade. Following are the key differences in grades:

• Extra virgin olive oil must meet numerous chemical parameters (including a free fatty acid content of 0.08 percent or less) and a sensory standard of zero defects (such as fermented or rancid flavors), with some fruitiness.
• Virgin olive oil. This grade has slight defects of aroma or flavor and meets a lower chemical standard, including higher free fatty acid levels. Both virgin and extra virgin olive oils must be extracted from the olives by mechanical means, without the use of solvents.
• Refined olive oil blends (includes pure olive oil and extra-light olive oil). If a virgin olive oil does not qualify for the virgin designation as defined by its acidity level and other factors, the oil is refined to remove off-odors and off-flavors. The result is a bland oil that is blended with small amounts of virgin olive oil to give it some olive flavor and color.

But since claims of “fake” olive oil abound, how do you know you are buying the real thing?

The reality of alleged olive oil fraud in the U.S. is more complicated than simply “real versus fake,” however. Purity problems—that is, the adulteration of olive oil with other oils like soybean or canola, or refined olive oil added to extra virgin olive oil—are rare. In most cases, the real problem is the mislabeling of olive oil grades—a quality issue—whereby lower grade “virgin” olive oil is sold with a label that says “extra virgin,” the highest grade. In addition, because the oil is perishable, olive oil that starts as extra virgin can be compromised by the time you buy it at the supermarket if bottling, storage, and distribution practices are inadequate.

This mislabeling is possible because there is a dearth of meaningful regulation in the market. California is leading the way to correct the problem with a California Department of Food and Agriculture standard for olive oil (the most stringent in the country) and a mandatory government sampling and testing program for California-produced olive oil under the Olive Oil Commission of California (OOCC).

However, about 95 percent of the olive oil consumed in the U.S. is imported—and this includes some of the finest olive oils in the world—so having some understanding of the ins and outs of imported olive oil is critical if you want to be an informed buyer.

We spoke with Alexandra Kicenik Devarenne, a co-founder of the Extra Virgin Alliance, an international trade association dedicated to olive oil quality, about what to note on bottles when choosing an extra virgin olive oil:

• If it seems too cheap to be extra virgin, it probably isn’t. Genuine extra virgin olive oil costs more to produce, so it should cost more to buy. If an oil labeled “extra virgin” is, say, $4.99 per liter, there’s a good chance it is “virgin” grade, with some minor flavor faults (see box). It’s okay to use virgin grade olive oil for cooking or for when you don’t need or want olive flavor, but many people prefer extra virgin for salads and other non-cooking uses.
• “Best before” or “harvest date.” Olive oil is at its best when it’s fresh during the first year after harvest, but a well-made, well-conserved extra virgin olive oil should have a two-year shelf life before opening (so don’t automatically reject oils from a previous harvest). Once opened, use it within a few months. “Best before” dates are most often two years from bottling.
• Country of origin (look for single region). Another issue is lack of transparency about “country of origin,” with the front label of some olive oils giving the impression that they are from one country, while the small print on the back reveals that they originated elsewhere. So no matter what the front label looks like, check the back label for the actual origin of the oil, which is often stated in abbreviations. In 2018, the manufacturer of Bertolli olive oil paid $7 million to settle a class action lawsuit that alleged, in part, that its labels misleadingly stated that some oils were “Imported from Italy,” when in fact the olives were grown or pressed in other countries.

In general, olive oil described on the label as coming from a specific area (either a whole country or a region within a country, such as Puglia and Liguria in Italy or Crete in Greece) tends to indicate a higher-quality oil. If multiple countries are listed, there is a greater chance that the oil is a bulk commodity oil from a packer. Packers are large corporations that own brands— often several—of olive oil but produce little or no oil themselves. (The majority of familiar supermarket brands are owned by these large corporations.) There is no obstacle to their buying and bottling good oil, but they tend to trade in cheaper commodity oils.

• Brands from actual olive oil producers or Estate Production. If an olive oil is labeled “Estate Production,” it should have been milled (the term for processing of olives into olive oil) and bottled on the farm where the olives were grown. The understanding and regulation of this term with respect to olive oil is generally based on its use in the wine industry, but enforcement depends on the region. Extra virgin olive oil brands that belong to the people who grew the olives and made the oil, or who worked closely with the farmers and processors to control quality, are more likely to be of higher quality (and higher price). You can sometimes learn more about the people behind the brand by visiting the company’s website, but be skeptical of gimmicky marketing stories.
• “Protected Designation of Origin” logos (PGI, DOP, DO, or AOC). Regulated by the European Union and regional governments, these logos guarantee that the oil was produced in a specific region of the labeled country using olive varieties traditionally grown in the area.
• Marketing seals, from the USDA Quality Monitoring Program, the North (NAOOA), the California Olive Oil Council (COOC), the Extra Virgin Alliance (EVA), the Olive Oil Commission of California (OOCC), and others. These usually indicate membership in an association or program and have varying quality standards and monitoring practices, which are detailed on the associations’ websites.
• Other information, including olive varieties, farming practices, and milling. Such descriptions on labels are usually a good sign because they indicate a more conscientious producer.

Additional take-home tips
Pay attention to the flavor! The oil should taste of fresh olives, ripe or green, with no flavors of rancidity (stale walnuts, crayons) or fermentation (likened to sweaty socks). If you just bought the oil and it tastes rancid—regardless of the date—take it back, just as you would do with other spoiled foods. Rancidity is not a safety issue, however. Be aware that bitterness is not a defect but rather a natural taste component in fresh green olives and a great flavor enhancer with the right foods, such as a hearty bean soup, tomato-based sauce, or grilled meat. Of note, some supermarket brands are making a big effort to improve quality, while some chains, including Wegmans and Fresh Market, are starting to review the products they sell. It’s worth tasting around for oils that suit your needs (cooking versus finishing).

For longer shelf life, olive oil should be protected from light, air, and heat. The single most important thing is to store the oil in a cool, dark cabinet. There’s no need to refrigerate it if you use it within a reasonable time. A year-long study published in the Journal of the American Oil Chemists’ Society in 2019 found that olive oil in dark glass bottles retained quality best, compared to olive oil stored in clear glass or plastic bottles (oxygen can pass through plastic but not glass). Another good option is olive oil packed in cans. Best of all is bag-in-box because the bag collapses as you use the oil, preventing oxygen exposure, plus the box is a perfect barrier to light. (Bag-in-box is also better for the environment since the lighter weight of this packaging leaves a smaller carbon footprint.)

LAST WORDS: The European Food Safety Authority allows bottlers of olive oil with high polyphenol content to make a heart health claim, since these (and other) compounds in olive oil have been linked to potential benefits. But keep in mind that olive oil is not the only healthful plant oil: With the exception of tropical oils, all plant oils (including canola, safflower, corn, and soybean) are also largely unsaturated and thus good choices. And many other foods besides olive oil—notably tea, fruits, and vegetables—are rich sources of polyphenols.