Adherence to the Mediterranean Diet Reduced Risk of Advanced Colorectal Cancer

Medical doctor drawing colon cancer on the virtual screen.

The Mediterranean diet – rich in fruits, vegetables, olive oil, legumes, whole grains and fish – has a number of well-known benefits when it comes to colorectal protection.

While adherence to the Mediterranean diet has been associated with lower risk of colorectal cancer or CRC in observational population studies, until recently it has been hard? to know specifically what elements of the diet are the healthiest.

Now a new study, presented at the 19th World Congress on Gastrointestinal Cancer of the European Society of Medical Oncology (ESMO) being held June 28 – July 1 2017 in Barcelona, Spain, suggests loading up on fish and fruit, and cutting back on soft drinks are the three most important things.

“We found that each one of these three choices was associated with a little more than 30% reduced odds of a person having an advanced, pre-cancerous colorectal lesion, compared to people who did not eat any of the MD components,” noted Naomi Fliss Isakov, PhD fromTel-Aviv Medical Center, in Tel Aviv, Israel.

“Among people who made all three healthy choices the benefit was compounded to almost 86% reduced odds,” Fliss Isakov added.

Causes of Colerectal Cancer
Colorectal cancer (CRC) is common and a leading cause of cancer-related death, which develops gradually from adenomatous and serrated polyps. [1] Combining the numbers of both men and women, colorectal cancer is the second leading cause of cancer death. The death rate, the number of deaths per 100,000 people per year, has been dropping for several decades. One reason for this is that colorectal polyps are now more often found by screening and removed before they can develop into cancers. Finding colorectal cancer at an early stage – before it metastasizes – increases the 5-year relative survival rate to aproximately 90%. [2]

Diet, weight and exercise
According to the American Cancer Society, the links between diet, weight, and exercise and colorectal cancer risk are some of the strongest for any type of cancer. [2] Explains Fliss Isakov: “Colorectal cancer (CRC) develops from intestinal polyps and has been linked to a low-fibre diet heavy on red meat, alcohol and high-calorie foods.”

Study design
Using dietary questionnaires from 808 people who were undergoing screening or diagnostic colonoscopies, the research team was able to dig down to look at the fine details of their daily meals.

All subjects were between 40 and 70 years old, without high risk of colorectal cancer. and answered a food frequency questionnaire. Each participant underwent anthropometric measurements, and a medical and lifestyle interview and filled a detailed semi-quantitative food frequency questionnaire (FFQ), adapted to the Israeli population and to the needs of this study.

In this study, adherence to the Mediterranean diet components was defined as consumption levels above the group median for fruits, vegetables and legumes, nuts and seeds, whole grains, fish and poultry and a high ratio of monounsaturated to saturated fatty acids, as well consumption below the median of red meat, alcohol, and soft drinks.

Study results
The investigators found that compared to subjects with clear colonoscopies, those who had advanced polyps reported fewer components of the Mediterranean diet (4.5?1.9 vs. 5.1?1.7, P=0.03). In the study’s multivariate analysis, this was significantly associated with lower odds of advanced polyps (OR=0.81, 0.73-0.90).

Yet even consumption of two to three components of the diet, compared to none, was associated with half the odds of advanced polyps. The study showed that adherence to 1 to 4, and 5 to 10 Mediterranean diet components were negatively associated with advanced colorectal polyps compared to none (OR=0.50, 95%CI 0.32-0.79, P=0.003 and OR=0.47, 95%CI 0.26-0.83, P=0.009, respectively).

Overall, odds were reduced in a dose response manner with additional Mediterranean diet components ? meaning that the more of these components people adhered, the lower their odds of having advanced colorectal polyps.

The researchers further showed that components of the Mediterranean diet which were negatively associated with advanced polyps, with adjustment for potential confounders and to all other dietary components were: low intake of soft drinks (OR=0.65, 0.44-0.97), high intake of fruit (OR=0.66, 0.45-0.95) and high intake of fish (OR=0.62, 0.42-0.91). Combined adherence to all three components was significantly associated with lower odds of advanced colorectal polyps (OR=0.14, 0.04-0.41).

Finally, after adjusting to account for other CRC risk factors, including other dietary components, the researchers narrowed in on high fish and fruit and low soft drinks as the best combo for reduced odds of advanced colorectal polyps.

Follow-up
The next step will be to see whether the MD is linked to lower risk of CRC in higher risk groups, she concluded.

“This large population-based cohort-control study impressively confirms the hypothesis of an association of colorectal polyps with diets and other life-style factors,” noted Dirk Arnold, MD, PhD, and ESMO spokesperson from Instituto CUF de Oncologia in Lisbon, Portugal.

“This stands in line with other very recent findings on nutritive effects, such as the potential protective effects of nut consumption and Vitamin D supplementation which have been shown earlier this year. However, it remains to be seen whether these results are associated with reduced mortality, and it is also unclear if, and when a dietary change would be beneficial. Despite this lack of information, it makes sense to consider this diet for other health-related reasons also,? Arnold added.

The researchers conclude that a prospective, large-scale studies may better clarify the relations between dietary pattern and colorectal neoplasia.


Last editorial review: June 30, 2017

Featured Image: Colorectal CancerCourtesy: ? 2017 Fotolia. Used with permission.

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