Three elements of Mediterranean diet most effective for reducing colorectal cancer risk
While the Mediterranean diet has been linked to a reduced risk for colorectal cancer, three key elements of the diet are most important for preventing the development of precancerous polyps, according to new research presented at the ESMO World Congress on Gastrointestinal Cancer.
The study showed that eating a diet high in fish and fruit, and low in soft drinks, was the best combination for preventing advanced colorectal polyps.
“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 [Mediterranean diet] components,” Naomi Fliss Isakov, PhD, from Tel-Aviv Medical Center in Israel, said in a press release. “Among people who made all three healthy choices the benefit was compounded to almost 86% reduced odds.”
To evaluate individual and combined components of the Mediterranean diet and their link to advanced colorectal polyp prevention, investigators performed a population-based case-control study of 808 consecutive individuals aged 40 to 70 years without a high CRC risk who underwent screening or diagnostic colonoscopy.
Using food frequency questionnaires, they evaluated the participants’ adherence to different components of the Mediterranean diet including higher intake of fruits, vegetables and legumes, nuts and seeds, whole grains, fish and poultry, a high ratio of monounsaturated-to-saturated fatty acids, and lower intake of red meat, alcohol and soft drinks.
Participants in whom advanced polyps were detected on colonoscopy reported adhering to significantly fewer components of the diet compared with those who had no advanced polyps (mean, 1.9 vs. 4.5 dietary components; P = .03). Further, multivariate analysis showed the mean number of components a participant adhered to was significantly associated with a reduced risk for advanced polyps (OR = 0.81; 95% CI, 0.73-0.9).
Notably, adhering to just one to four of the diet components was associated with half the risk for advanced colorectal polyps compared with adhering to none of the components (OR = 0.5; 95% CI, 0.32-0.79). However, the more components of the diet a participant adhered to, the lower their risk.
After adjusting for other CRC risk factors and dietary components, the investigators showed that low consumption of soft drinks (OR = 0.65; 95% CI, 0.44-0.97), high consumption of fruit (OR = 0.66; 95% CI, 0.45-0.95) and high consumption of fish (OR = 0.62; 95% CI, 0.42-0.91) were the dietary components with the strongest negative associations with advanced colorectal polyps, and adhering to all three of these was significantly associated with a reduced risk (OR = 0.14; 95% CI, 0.04-0.41).
“This large population-based cohort-control study impressively confirms the hypothesis of an association of colorectal polyps with diets and other lifestyle factors,” ESMO spokesperson Dirk Arnold, MD, PhD, from Instituto CUF de Oncologia in Lisbon, Portugal, said in the press release. “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.”
Fliss Isakov noted in the press release that further research will evaluate whether the Mediterranean diet is associated with lower CRC risk in higher risk groups. – by Adam Leitenberger
Fliss Isakov N, et al. Abstract O-023. Presented at: ESMO World Congress on Gastrointestinal Cancer; June 28-July 1, 2017; Barcelona.
Disclosures: Healio Gastroenterology was unable to confirm the researchers’ relevant financial disclosures at the time of publication.