The Secret Behind the Mediterranean DietJanuary 2010
By Dale Kiefer
Natural Cancer Prevention
While epidemiologic and observational studies have long indicated the Mediterranean diet is protective against cancer,1,28,29 recent laboratory studies have demonstrated specific mechanisms and pathways by which olive oil constituents inhibit a variety of cancers at multiple stages.30-36
One mechanism involves suppression of fatty acid synthase, an enzyme that helps convert carbohydrates to fat in the human body. Natural compounds have been shown to induce anti-cancer effects by suppressing fatty acid synthase.30
Since olive oil polyphenols have been suggested to possess biological activities that may explain the health-promoting effects of the Mediterranean diet, researchers examined the effects of olive polyphenols on fatty acid synthase production in cancerous breast tissue. Extra virgin olive oil polyphenols, lignans, flavonoids, and secoiridoids were found to drastically suppress fatty acid synthase protein expression in breast cancer cells.30 These findings provided direct evidence of a cancer-protective effect from olive oil polyphenols, offering a previously unrecognized mechanism for olive oil-related cancer preventive effects.
British researchers have also reported potent anti-cancer activity by olive polyphenols. Working with an olive oil extract containing the polyphenols hydroxytyrosol, tyrosol, and various secoiridoid derivatives, including oleuropein, investigators examined the effects of the extract on human colon cancer cells growing in culture.37
The extract was found to inhibit cancer cell proliferation. Olive oil polyphenols were shown to disrupt a chemical process that ordinarily results in increased cyclooxygenase-2 (COX-2) expression. COX-2, a target of common anti-inflammatory drugs, is known to be involved in the promotion of a variety of cancers.38,39 “Our data suggest that olive oil polyphenols may exert chemopreventive effects in the large intestine by interacting with signaling pathways responsible for colorectal cancer development,” the researchers concluded.37
Another laboratory study, conducted in Ireland, addressed the ability of colon cancer cells to metastasize, or spread.32 Investigators examined the activity of individual olive oil polyphenols against the invasiveness of human colon cancer cells using a standardized assay. “Phenols from virgin olive oil have the ability to inhibit invasion of colon cancer cells,” researchers concluded. Furthermore, the natural olive compounds inhibited cancer cell invasion “at different levels of the invasion cascade.”
Another recent laboratory study concluded that an extract of Greek olives, administered at varying concentrations, was significantly effective at suppressing proliferation of gastric cancer cells.33 At the greatest concentrations, the olive polyphenol extract significantly induced apoptosis, or programmed cell death. All concentrations of the extract reduced inflammation-related protein production by the cancer cells. The researchers concluded, “The extract exhibits gastric cancer preventive efficacy by limiting cell proliferation, inducing cell death and suppressing inflammation in [stomach cancer] cells.”
Previous research has also shown that olive polyphenols exhibit antibiotic activity against Helicobacter pylori, the bacterium now known to be responsible for the great majority of cases of ulcer and implicated in the development of gastric cancer. In laboratory experiments, Spanish researchers demonstrated that olive polyphenols exerted strong anti-bacterial activity against eight different strains of the problematic bacteria, including three that are resistant to antibiotics commonly used against them.40
Potential Protection for Aging Bones
Olive oil polyphenols may help protect aging bones from becoming fragile. A recent pre-clinical model of post-menopausal bone loss found that olive polyphenols protect against bone loss. Rats fed a steady diet of olive polyphenols avoided the bone loss that those deprived of them experienced. “Polyphenol consumption seems to be an interesting way to prevent bone loss,” concluded researchers.5 In earlier work, the same team of French researchers found that olive oil and its primary polyphenol oleuropein can prevent inflammation-induced loss of bone mineralization (osteopenia)—a prelude to full-blown osteoporosis—in rats that had undergone removal of the ovaries.41
Extra virgin olive oil is unique among plant-derived oils in that it provides both heart-healthy monounsaturated/polyunsaturated fats and a significant amount of bioactive antioxidant, anti-inflammatory polyphenols. Described as “the most genuine component of the Mediterranean diet,”42 olive oil is now emerging as a critical component of a healthy diet. Research has demonstrated or suggested that olive oil polyphenols play an important role in protecting humans from heart disease, cancer, and age-related bone loss. These effects are due in part to synergistic activity among various natural polyphenols,16 which reduce inflammation and decrease oxidative stress, among other beneficial activities.
Research also indicates that the combination of omega-3 fatty acids with olive oil polyphenols offers enhanced benefits, beyond those provided by either nutrient alone.20-23
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