Mediterranean-style Diet and Cancer: What does the Science Show?
While it has been known for many years that a Mediterranean Diet (Med Diet) is protective for the heart, there is accumulating evidence showing that it also may play a role in lowering the risk for several types of cancer such as breast, endometrial, head and neck, colorectal, gastric, liver, and prostate cancer. Mediterranean diets are anti-inflammatory as they have been associated with lower levels of biomarkers (i.e., blood tests) of inflammation (e.g., C-reactive protein or CRP) compared to diets that are more pro-inflammatory (e.g., high in processed foods, refined grains/sugars, red meat and low in whole plant-based foods).
So, what does a traditional Mediterranean Diet include?
It consists of a high consumption of plant-based foods, in particular fruits, vegetables, whole grains, nuts, legumes, seeds and regular intake of fish, especially fish high in Omega-3 fatty acids. Fish high in Omega-3 fatty acids are salmon, mackerel, sardines, trout, and herring. Red meat is eaten typically no more than a few times a month. Extra virgin olive oil (EVOO) is the main source of healthy dietary fats. EVOO is the least processed of the types of olive oils and therefore has higher amounts of anti-oxidants. Spices and herbs are used to season foods, many of which have been found to have anti-cancer properties. While a traditional Med Diet often includes a moderate consumption of red wine with meals, the risk of increasing certain cancers must be taken into consideration on an individual basis.
Pro-inflammatory diets include a low intake of fruits and vegetables and high amounts of red meat, processed meats, refined grains/sugars, and other processed food sources, which are often consumed daily in the typical American diet. Sadly, most of the patients I see in practice have been eating the typical American diet for years and many do not even consider diet as a contributing factor in the development of cancer.
So, what does the scientific evidence show?
In 2017, a large review of 27 research studies, which included over two million participants, found that individuals who had the highest adherence rates to a Med Diet had a 14% lower risk of dying from cancer. In particular, risk was found to be lower for breast cancer (57%), head and neck cancer (51%), liver cancer (42%), gastric cancer (28%), colorectal cancer (18%) and prostate cancer (4%). While the study found lower rates of recurrence (39%) among cancer survivors who adhered to a high versus low Mediterranean dietary pattern, the results were not statistically significant. However, only one study included in the review paper focused on cancer survivors and recurrence.
As far as single studies, in 2017 researchers from the Netherlands found that women who had higher adherence to a Med diet were 40% less likely to develop estrogen receptor negative breast cancer, which typically has a poorer prognosis that the more common estrogen receptor positive breast cancer, but rates of both types of breast cancer were lower in those women who followed a Med diet. Another study addressing endometrial cancer among Italian women found a reduced risk, 57%, among those who more closely followed a Med diet.
A study published early in 2019 revealed that a medium-to-high adherence compared to low adherence of a Med Diet was associated with a 52% lower risk of head and neck cancer, which is very close to that found in the large review study previously discussed. Another study published this year examined the relationship of a Med Diet and highly aggressive prostate cancer risk. The researchers found a 34% reduction in risk among men who consumed a Med-style diet compared to those who did not.
With all of the mounting evidence pointing to the cancer risk-reduction potential of a Mediterranean diet, why not consider trying to adopt this dietary approach. While both the American Cancer Society and the American Institute for Cancer Research may not specifically mention a Mediterranean Diet in their nutrition recommendations, they do advocate for a diet rich in fruits, vegetables, and whole grains and low in red meats, refined grains, and processed foods, all of which are part of the Med Diet.
Being a long-time advocate for a Mediterranean style diet for its health-enhancing benefits, I would be more than happy to help guide you towards a dietary pattern more aligned with the Med Diet. Remember, Food is Medicine!