Introduction
Probiotics are living microorganisms that offer health benefits by aiding digestion, producing vitamins, and combating harmful microorganisms, commonly found in yogurt, fermented foods, beauty products, and dietary supplements, resembling naturally occurring microorganisms in the human body.
Probiotics regulate intestinal flora, strengthen the intestinal barrier, protect against pathogens, and enhance the immune system by symbiotically interacting with the 100 trillion bacteria in the human intestine.
The most commonly used species in the market are Lactobacillus (sps: acidophilus, fermentum, casei, johnsonii, gasseri, Plantarum, paracasei, rhamnosus, and salivarius), Bifidobacterium (sps: animalis, adolescentis, breve, bifidum, and longum), along with the above-mentioned species also some other strains have shown beneficial activity which includes, Akkermansia spp., Faecalibacterium spp., and Roseburia spp.
It is known that the immunity of cancer patients will be reduced due to cancer therapies/cancer treatments like chemotherapy and radiotherapy, but numerous studies showed that probiotics can help cancer patients in coping with cancer.
Probiotics and Cancer
Many studies have shown that probiotics have been effective in regulating the proliferation and apoptosis of cancer cells, the studies are as follows,
The strain Lactobacillus rhamnosus GG has inhibited and induced apoptosis in human Caco-2, DLD- 1, and HT-29 colon cancer cells lines.
The strain, Salmonella typhimurium, has effectively increased the production of Short-chain-fatty-acids (SCFAs), as the SCFAs are the source of energy for colon cells by maintaining the acidic environment in the intestine, inhibiting the secondary bile acids formation, and promoting apoptosis of the cancer cells.
Lactobacillus, Bifidobacterium, Propionibacterium freudenreichii, and Streptococcus salivarius subspecies can produce Conjugated linoleic acid (CLA), CLA can induce the expression of apoptosis genes Bcl-2, caspase-3, 9, therefore inhibiting the spread of colon cancer cells.
It has been observed that the treatment consisting of TGF-β receptor blockers combined with probiotics has enhanced the antitumor response, inhibiting tumour growth.
Probiotic treatment improves microbial structure, increases diversity, and shows promise as a biologically-based alternative therapy for preventing and treating colorectal cancer in susceptible individuals.
Clinical trials
| Cancer type | Treatment received | Objective | Intervention | Outcome | Side effects |
| Cervical cancer | Radiotherapy | Improve diarrhoea | 1.75 billion live Lactobacillus acidophilus (LA-5) & Bifidobacterium animalis subsp (BB-12) bacteria, in 3 capsules per day from day 1 to the end of radiotherapy. | Incidence of diarrhoea is lower in the probiotic group over the placebo group, reduction in the rate of anti-diarrhoea drug(loperamide) | No toxicity is reported related to probiotics |
| Colorectal cancer | Postoperative chemotherapy | Improve diarrhoea | The strain Lactobacillus rhamnosus GG supplements. | Patients in the probiotic group and placebo group experienced mild and III or IV grade diarrhoea respectively. | |
| Lung cancer | surgery | Improve diarrhoea | C butyrate tablets, 3 times a day for 3 weeks and fibre & from the starting of chemotherapy. | The incidence of I grade diarrhoea has reduced in the probiotic group. | |
| Gastric cancer | Radiotherapy & chemotherapy | Improve diarrhoea | Probiotic & fibre rich nutritional food, enteral nutrition for 7 consecutive days | Diarrhoea cases were reduced in the intervention group. | |
| Head & neck cancer | surgery | Improve oral mucositis | Lactobacillus brevis CD2 tablets, 6 times a day from the day first day of treatment until a week later of the last treatment | Patients in the probiotic group and placebo group experienced mild and III or IV grade diarrhoea respectively. Also, the completion rate of anti-cancer treatment is improved significantly in the interventional group. | |
| Colorectal cancer | Improve inflammation | 30 billion probiotic mixed preparation twice a day for 6 months. | The inflammatory cytokinins (TNF-α, IL-6, 10, 12, 17A, 17C, 22) in the probiotic group. |
Probiotics and Cancer side effects
Cancer treatments such as radio chemotherapy can cause gastrointestinal distress, damage the intestinal mucosal barrier, increase permeability, leading to the spread of intestinal flora and endotoxins to other organs, causing systemic inflammation and multiple organ failure.
Studies showed that the antitumour side effects of the probiotics are related to the innate immunity, as the acyl dipeptides a component of the probiotics cell wall can alleviate the mucosal damage that is caused by the antibiotic chemotherapeutics, as they can stimulate the intracellular pattern recognition receptors NOD2.
Probiotics, specifically Lactobacillus CD2, have been effective in preventing 70% of severe oral mucosal damage induced by high dose chemotherapy and hematopoietic stem cell transplantation (HSCT) without any adverse reactions, while also restoring the intestinal mucosal barrier.
Also, probiotics can reduce the event of graft-versus-host-disease (GVHD), which limits haematopoietic stem cell transplantation.
Probiotics and other therapeutic uses
Some studies have shown that probiotics help in preventing and treating conditions related to allergy.
Intake of probiotics had beneficial effects on hepatic encephalopathy, even though it is not considered a conventional treatment for liver disease.
Risk factors and side effects
The risk factors can include individuals who are having issues related to the immune system, premature infants, hospital patients who are seriously ill, therefore the benefits and risks are to be weighed carefully and the advice of a health professional is to be taken before consuming probiotics.
Side effects may include, the transmission of antibiotic resistance genes from probiotic organisms to the microorganisms of the digestive tract or intestinal flora, release of harmful substances from the probiotics.
