Drinking a cup of tea every day may improve survival for patients with colorectal cancer

Key takeaways:

• Higher intake of a subclass of flavonoids reduced mortality in patients with colorectal cancer.
• Tea, a major contributor of flavonoid intake, also improved survival in patients with colorectal cancer.

Higher intake of a subclass of flavonoids was linked to reduced mortality for those diagnosed with colorectal cancer, and small increases in consumption of foods rich in the compound, like tea, may improve survival, data show.

Flavonoids are phytochemical compounds present in many fruits, plants and vegetables. They are divvied into several subclasses based on molecular structure: proanthocyanins, flavan-3-ols, flavanones, flavanols, anthocyanins and flavones, Shanshan Shi, MD, MS, a laboratory supervisor at the Harvard T.H. Chan School of Public Health’s Song Lab, and colleagues wrote in the American Journal of Clinical Nutrition.

There is some experimental evidence supporting the anti-cancer effects of flavonoids “owing to their capability of interfering with epigenetic signaling cascades responsible for tumorigenesis and metastasis,” the researchers wrote.

However, it is unknown if intake affects colorectal cancer (CRC) survival specifically, they added. CRC is the second-leading cause of cancer death worldwide, accounting for 930,600 deaths in 2020.

Shi and colleagues conducted a prospective study to evaluate the association between post-diagnostic flavonoid intake and CRC-specific and all-cause mortality in 2,552 patients enrolled in the Health Professionals Follow-up Study and the Nurses’ Health Study. Using validated food frequency questionnaires, the researchers assessed the intake of total flavonoids and their subclasses.

Shi and colleagues found that total flavonoid intake was not associated with mortality, but higher intake of flavan-3-ol was linked to lower all-cause and CRC-specific mortality.

The multivariable HRs per one standard deviation were:

• 0.83 (95% CI, 0.69-0.99) for CRC-specific mortality and
• 0.91 (95% CI, 0.84-0.99) for all-cause mortality.

The researchers also noted a similar beneficial association for tea. Not only did the researchers find that patients who drank one to three cups of tea (8 oz. per cup) already had a lower CRC-specific mortality than non-drinkers, but as “the major source of flavan-3-ols and proanthocyanins,” tea showed an inverse association with both all-cause and CRC-specific mortality, with multivariable HR per 1 cup of tea each day of 0.9 (95% CI, 0.85-0.95) and 0.86 (95% CI, 0.75-0.99), respectively.

“These findings suggest the survival-improving benefit of a higher intake of flavan-3-ols in CRC survivors and provide novel evidence for dietary modifications in cancer management,” Shi and colleagues wrote. “More prospective studies are warranted to replicate and confirm our findings and further laboratory studies to better understand the biological mechanisms.”