Protective benefits of dietary flavonoids against colorectal cancer
Local and systemic 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 reducing these risks. One of these dietary factors that has received attention in recent years is the beneficial role of flavonoids, mainly present in fruits and vegetables but also in red wine and dark chocolate, in improving intestinal health in providing antioxidant and anti-inflammatory properties.
Flavonoids are a group of compounds divided into six subclasses: isoflavones, anthocyanidins, flavanols, flavanones, flavones, and flavonols. Once consumed, the gut microbiota metabolizes dietary flavonoids, which exert prebiotic and antimicrobial properties and help inhibit gastrointestinal inflammation through direct and indirect mechanisms. Recent findings by Carola and colleagues, published last month in Nutrients, found an inverse relationship between CRC risk and high dietary flavonoid intake in patients from an Italian cohort. These findings are critical to helping public health officials expand people’s knowledge about CRC prevention, especially as CRC continues to rise.
Italy has a heavy burden of CRC and the number of cancers has been steadily increasing in recent years. GlobalData epidemiologists estimate that in Italy there will be 56,000 incident cases of CRC in men and women aged 18 and over by the end of this year. This number is expected 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 cases of CRC, and 200 controls, matched by age and sex, were recruited from two university hospitals in Milan, Italy. Participants between the ages of 20 and 85 took part in a standardized food frequency questionnaire to determine their level of intake of the six flavonoid subclasses. A significant relationship was found between the risk of CRC and the intake of anthocyanidins and flavanones, two measured flavonoid subclasses; the odds ratio was 0.24 for anthocyanidins and 0.18 for flavanones.
The colon cancer odds ratio for the highest tertile 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 tertile versus the lowest tertile for intake was 0.16 for anthocyanidins and 0.12 for flavanones. These results show that higher consumption of the flavonoid subclasses, anthocyanidins and flavanones, found in foods such as blueberries, black beans, red onions and citrus fruits, provided significant protective benefits against CRC. .
This valuable epidemiological information on the impact of diet, particularly the intake of anthocyanidins and flavanones, on the risk of developing CRC signifies the magnitude and potential of flavonoids for medical benefits. Increasing research and public health messaging in this area can increase awareness of healthy eating to reduce cases of CRC and, therefore, disease burden.