Flavonoid-rich diet and beneficial bacteria attributed to low colorectal cancer in Indian population – Gut microbiome study

At our Probiotia Asia event held in Singapore, Dr. Vineet Sharma from the Indian Institute of Science Education and Research (IISER) said CRC was the third most common cancer and second leading cause of cancer death globally, “but surprisingly lower in India, (which is) attributed to high flavonoid consumption​.”

Despite this, he stressed that CRC risk was on the rise in India, due to the growing adoption of a Western lifestyle and lack of physical activity.

Acting on the lack of early detection techniques for CRC, Sharma and his team conducted India’s first CRC microbiome and metabolome study.

Study findings​

The study recruited both CRC patients (early to late stages of cancer) and healthy individuals to compare a diseased gut metagenome with a healthy one.

The study found an association of bacteroides and other bacterial taxa in the faeces of the CRC group.

The researchers then constructed a gene catalogue and metabolome for colorectal cancer and found 33 gene markers and 20 taxonomic markers, which could be used to diagnose CRC.

There was also microbiome dysbiosis in CRC patients. Dysbiosis is the disruption of the normal microbiome content leading to a reduction in pathways related to the biosynthesis of six essential amino acids (Leucine, Isoleucine, Lysine, Phenylalanine, Tryptophan and Valine) out of the nine essential amino acids the body requires.

From this, researchers said these cohort-specific biomarkers could be used in non-invasive diagnosis of CRC, from faecal samples alone.

Sharma said: “When we use these markers, it can clearly segregate the CRC patients and healthy individuals​.”

Flavonoid degradation​

According to him, the typical Indian diet is rich in flavonoids, which can be found in tea, coffee, terminalia bark, fenugreek seeds, mustard seeds, cinnamon, red chili powder, cloves, and turmeric.

He explained that flavonoids have a role to play in the prevention of cancer, CVD, type 2 diabetes and other diseases.

But, the presence of certain gut bacteria can degrade these flavonoids by cleaving the C-ring of the flavonoid molecules.

For instance, in the group with CRC, bacteria such as veillonella parvula, bacteroides fragilis​ were present, where other research have found its possible role in inducing epithelial cell changes and modulate the mucosal immune responses, resulting in CRC progression.

However, in the group without CRC earlier, faecal samples showed higher levels of prevotella​ bacteria compared to the CRC.

The abundance of prevatolla​ is attributed to a diet higher in plant materials and carbohydrate. We reported this earlier​ when researchers from IISER conducted the largest gut microbiome study of the Indian population.

The degradation of beneficial flavonoids thus play an important role in cancer progression in the Indian cohort.

Indian-specific probiotics​

Sharma said the Indian gut microbiome was uniquely different from other parts in the world due to its lifestyle, food habits, and a large population of vegetarians.

He said these findings provide motivation to develop Indian-specific probiotics, which can therapeutically target intestinal microbiome by promoting beneficial bacteria and inhibiting potentially pathogenic species.

He also added that most probiotic bacteria were imported from other countries, with the top companies in the Indian market being Amul, Nestle, Mother Dairy and Yakult.

He reiterated that the Indian population needed a probiotic that was specially designed for the Indian gut microbiome.