KC: Research regarding olive oil’s beneficial relationship to heart health is strong, but is still limited regarding cancer risk. You may have heard about the Spain-based PREDIMED study, where women who got the greatest proportion of their calories from extra virgin olive oil had a lower risk of breast cancer than those with the least. In this and other studies showing possible lower risk though, there are many caveats, including that some studies were very small or did not adjust for important risks like alcohol. AICR’s comprehensive continuous update project (CUP) on breast cancer prevention so far has not identified olive oil as protective.
Extra virgin olive oil contains high levels of tocopherols (compounds related to Vitamin E that may offer protective effects) and natural plant compounds called polyphenols. In laboratory studies, these compounds are studied for their potential to reduce DNA damage, decrease cancer cell growth, and increase the self-destruction of cancer cells.
In studies where olive oil is associated with reduced breast cancer in humans, it reflects a greater proportion of calories coming from olive oil. That’s important, since simply adding calories could lead to weight gain, and overweight increases risk of postmenopausal breast cancer (and ten other cancers). One more key point: when greater olive oil consumption links with lower cancer risk, it may be because it tends to go hand in hand with overall healthy eating that includes more vegetables and other healthful plant foods. Olive oil is a great choice, but research provides much stronger support for the importance of an overall eating pattern with mostly plant foods and healthy weight than your choice of oil.
What is the difference between pure olive oil, light olive oil, virgin olive oil and extra virgin olive oil?
KC: In the United States we categorize olive oils into extra virgin (sometimes referred to as EVOO), virgin, light and classic (pure) olive oil. All these oils are made by extracting the juice of olives. All olive oils, like any other fat, contain about 120 calories per tablespoon. Extra virgin olive oil is the first product of the extraction process, and thus has the strongest flavor and aroma of the three types. Virgin olive oil is also from the first pressing but is of slightly lower quality. Light olive oil refers to the absence of flavor, which makes it appropriate for dishes that would otherwise clash with the stronger flavored oils. Classic or pure olive oil typically results from a mixture of virgin olive oil and refined oil. Nutritionally, the fat in all three types of olive oil is mainly monounsaturated fat (MUFA). When MUFA is substituted for saturated fat, it lowers LDL (“bad”) cholesterol without reducing HDL (“good”) cholesterol. Studies linking greater use of olive oil with lower risk of heart disease generally don’t look at specific types of olive oil. However, both heart health and other possible health benefits may also relate to anti-inflammatory, antioxidant benefits of several natural compounds in olive oil. Extra virgin oil offers the most potential health benefits because it is the least processed and retains more of these compounds, including squalene, polyphenols and tocopherols (related to vitamin E).
Karen Collins, MS, RDN, CDN, FAND / American Institute for Cancer Research