Local and systematic inflammation and oxidative stress contribute to the development and progression of colorectal cancer (CRC); evidence in the literature suggests that diet plays a vital role in lowering such risks. One such dietary factor that has gained attention in recent years is the beneficial role of flavonoids, mainly found in fruits and vegetables but also in red wine and dark chocolate, in improving intestinal health by providing antioxidative and anti-inflammatory properties.
Flavonoids are a group of compounds divided into six sub-classes: isoflavones, anthocyanidins, flavanols, flavanones, flavones and flavonols. Once consumed, the gut microbiota metabolises the dietary flavonoids, which exert prebiotic-like and antimicrobial properties and help inhibit gastrointestinal inflammation through direct and indirect mechanisms. Recent findings from Carola and colleagues, published last month in Nutrients, found an inverse relationship between the risk of CRC and high dietary flavonoid intake among patients from an Italian cohort. These findings are instrumental in helping public health officials expand people’s knowledge of CRC prevention, especially as CRC continues to rise.
Italy has a high burden of CRC, and the number of cancers has been steadily rising in recent years. GlobalData epidemiologists estimate that in Italy, there will be 56,000 incident cases of CRC in men and women aged 18 years and older by the end of this year. That number is projected to increase to 63,000 cases by the end of 2031 (Figure 1).
This 2017-2019 case-control study by Carola and colleagues had 100 confirmed CRC cases, and 200 controls, matched by age and sex, were recruited from two university hospitals in Milan, Italy. Participants aged 20–85 years took part in a standardised food frequency questionnaire to determine their intake level of the six sub-classes of flavonoids. A significant relationship was found between CRC risk and the intake of anthocyanidins and flavanones, two sub-classes of flavonoids measured; the odds ratio was 0.24 for anthocyanidins and 0.18 for flavanones.
The odds ratio of colon cancer for the highest versus the lowest tertile for intake was 0.32 for anthocyanidins and 0.22 for flavanones. The odds ratio for rectal cancer for the highest versus lowest tertile for intake was 0.16 for anthocyanidins and 0.12 for flavanones. These results show higher consumption of the flavonoid sub-classes anthocyanidins and flavanones, found in foods such as blueberries, black beans, red onions and citrus fruits, offered significant protective benefits against CRC.
This valuable epidemiological insight into the impact of diet, in particular anthocyanidins and flavanones intake, on the risk of developing CRC signifies the magnitude and potential of flavonoids for medical benefits. Increased research and public health messaging in this area can increase awareness around a healthy diet to reduce CRC cases and, thus, disease burden.