By Donna Feldman, MS, RD

While much of the interest in the Mediterranean diet has focused on the beneficial effect on heart health, this style of eating has another possible benefit - it is associated with a lower risk of cancer. The reasons for this effect aren’t clear. It’s likely that several food components work together against cancer.

Higher omega 3 fats
One key difference in the Mediterranean diet is the higher ratio of omega 3 fats to omega 6 fats. High fish consumption accounts for much of this difference, as fish are the major dietary source of omega 3 fats. Also, olive oil is the predominant food oil, not the high omega-6 vegetable oils common in the U.S., and other many other Western countries. As a result, the omega 6-to-omega 3 ratio gets skewed much lower by a Mediterrnean diet. Omega 3 fats are anti-inflammatory, and are suspected of having other anti-cancer properties, such as inhibition of cell proliferation and tumor formation.

Plant foods
Another major factor of the Mediterranean diet is the reliance on plant foods as the basis of the diet. Whole grains, fruits and vegetables make up the base of the pyramid. As a result, daily intake of plant fibers, antioxidants, vitamins, minerals and numerous other biologically active food components is high. In particular, fiber, antioxidants, vitamin C, selenium and glutathione are associated with lower cancer risk (Eur.J.Cancer Prev. 2004 Jun;13(3):219-30). Mediterranean foods are rich in all these.

Olive oil may also have unique protective effects. According to the American Institute for Cancer Research (www.aicr.org), olive oil contains over 30 plant compounds that show anti-inflammatory and anti-oxidant effects. Increased self-destruction of cancer cells and slowed development are other possible effects. More research will clarify these effects.

Isn’t wine protective?
Resveratrol, recently in the news as a promising antioxidant, is only one of many substances found in grapes and wine that may be protective against cancer. It does have some antioxidant and anti-mutagenic properties (www.pdrhealth.com/drug_info/nmdrugprofiles/nutsupdrugs/res_0224.shtml). Grapes and wine contain several other known antioxidants, such as quercetin and gallocatechins, which are found in many fruits. So relying on wine for antioxidants is unnecessary. Certainly, as part of a Mediterranean eating plan, moderate wine consumption can contribute health benefits. Simply drinking more wine on top of an unhealthy diet is unlikely to be helpful.

Will a Mediterranean diet cure cancer?
The research on Mediterranean foods and cancer is, so far, all about cancer incidence. As such, the data say more about the possibility that this type of diet suppresses cancer development. It doesn’t say anything about the possibility that a Mediterranean diet will cure cancer that already exists. In fact, no particular diet is known to cure cancer. Certainly, any cancer patient who wants to switch to this diet during treatment or recovery should consult with his or her oncologist and dietitian. Some food components could interfere with drug treatments, and a patient’s personal health care team would be best equipped to evaluate those concerns on an individual basis.

Conclusion
The preventative effect of a traditional Mediterranean diet on cancer incidence has been documented. What is harder to measure is exactly which aspects of the diet cause the protective effect. The message is that, if you are looking at the Mediterranean diet for cancer prevention, you can’t pick and choose certain foods, like fish or olive oil, while ignoring the basic food plan. The whole diet seems to work as a package. Fortunately, the package is full of simple, great-tasting food that shouldn’t have a detrimental impact on your lifestyle, but may have a beneficial impact on your health.