Most bacteria species used as probiotics are under the genera Bifidobacterium and Lactobacillus; the genus Bifidobacterium contains approximately 57 subspecies, and it’s the dominant bacterial population in the gastrointestinal tract; the changes in the number of their population are one of the most frequent situations that are present on gastrointestinal diseases like inflammatory bowel disease, colorectal cancer, or/and irritable bowel syndrome. Recently Bifidobacterium spp has caught attention in the cancer field because of its pro-apoptotic effects. Many studies have been made regarding colorectal cancer to demonstrate this effect. Evidence from many studies suggests mechanism probiotics benefit colorectal cancer, including improvement in the host’s immune response, induction of apoptosis, and inhibition of tyrosine kinase signaling pathways, the epidermal growth factor receptor pathway on of them. Some species of Bifidobacterium can decrease carcinogen-induced DNA damage, pre-neoplastic lesions, and tumor in colons of rats, according to previous studies.

Sepideh Bahmani and colleagues conducted a study in 2019 resulting in Bifidobacterium bifidum being effective in combating cancer cells and associated with improved gastrointestinal cancer and concluded that the produced cell-free supernatants could inhibit the growth of cancer cells.

Bifidobacterium and Lactobacillus exert anticancer effects through the production of antioxidative enzymes, binding to reactive oxygen species, chelating heavy metals, neutralizing carcinogens, and they can regulate the cell cycle in cancer cells, inhibiting their proliferation, making them susceptible to apoptosis. The mechanism of action shown in different studies in which Bifidobacterium can act on cancer cell apoptosis resistance is via upregulation and downregulation of effective genes with pro-apoptotic and anti-apoptotic activities.

In a recent study by Zeinab Faghfoori et al., they found that the secretion metabolites of Bifidobacteria spp can induce intrinsic and extrinsic apoptosis pathways in human colorectal cancer cells.

With all the discussion and conclusions of different studies regarding the anti-cancer effect of Bifidobacterium species, we can conclude that, as for now, it is safe to use as a supplement in patients with cancer, especially colorectal cancer. More studies need to be made regarding which species of Bifidobacterium has the most benefits for battling against cancer and if there is a proper dose to achieve this effect.

Faghfoori, Z., Faghfoori, M.H., Saber, A. et al. Anticancer effects of bifidobacteria on colon cancer cell lines. Cancer Cell Int 21, 258 (2021).