Different meta-analyses suggest that an intake of probiotic foods such as yogurt may help in reducing the risk of lung cancer and colorectal polyps and in reducing diarrhea after radiation treatment for cancer and infection rates after colon cancer surgery. However, researchers suggested carrying out more well-designed studies to establish these findings. Probiotics may also be a rare cause of sepsis in those with compromised immunity. Hence, cancer patients who are undergoing treatment, or those who are candidates for immunotherapy should not take probiotics and yummy probiotic foods such as yogurt parfait without consulting their oncologist and nutritionist.
What are Probiotic Foods?
Probiotics are good, beneficial live bacteria and yeasts that are known to keep our gut healthy. The word “Probiotic” was derived from the Latin preposition “pro,” which means “for” and the Greek word “biotic” which means “bios” or “life”. Different parts of our body including the gut, mouth, skin, lungs, vagina and urinary tract, host beneficial microorganisms.
Probiotic foods are those foods that contain live and active beneficial bacteria. Many of the yummy foods that we eat such as yogurt parfait, Greek yogurt and cheese may contain probiotics. Probiotics or the good, helpful bacteria helps in removing the bad bacteria, and aids in maintaining a natural balance in our body, keeping our body healthy and functional.
Two major types of probiotic bacteria are Lactobacillus and Bifidobacterium.
An example of a probiotic yeast is Saccharomyces boulardii.
Examples/Sources of Probiotic Foods
The good bacteria or yeast in our body can be increased by taking probiotic foods, drinks and supplements.
Some examples of probiotic foods include:
- Yogurt and Cheese – Fermented dairy foods
- Pickles – A fermented food
- Kefir – Fermented probiotic milk
- Traditional buttermilk – Another fermented dairy drink
- Sauerkraut – Finely shredded cabbage fermented by lactic acid bacteria.
- Tempeh, Miso, Natto – Fermented soybean product.
- Kombucha – Fermented Green Tea
Use of probiotics are known to provide several health benefits including:
- Decreasing infectious diarrhea and treatment-associated diarrhea
- Reducing Irritable Bowel Syndrome and Inflammatory Bowel Disease
- Reducing stomach pain and bloating
- Modulating immune system
Whole grains and fruits when added to Greek yogurt, make a delicious treat called yogurt parfait with considerable health benefits. “Parfait” in “yogurt parfait” means perfect. Yogurt parfait is equally enjoyed by both children and adults. Different varieties of yogurt parfait are also designed by nutritionists for cancer patients with immense weight loss. Randomly including yogurt parfait or any probiotics in a cancer patients’ diet is however not advisable unless recommended by their oncologist or nutritionist.
Probiotic Foods Intake in Cancer Care and Prevention
Different studies show that the intake of probiotic foods such as yogurt can be beneficial in reducing the risk of specific cancers and also benefit certain cancer patients.
Probiotic Foods/Yogurt Consumption and Cancer Risk
In a recent study published by the researchers of Sichuan University in China in 2019, they did a meta-analysis to evaluate the association between fermented dairy foods intake (such as probiotic yogurt) and cancer risk. The data for the analysis was obtained through literature search in PubMed, Embase and CNKI databases through July 2018. A total of 61 studies with 1,962,774 participants and 38,358 cancer cases were included in the study. (Kui Zhang et al, Int J Cancer., 2019)
The study found that probiotic yogurt consumption may significantly decrease bladder cancer and colorectal cancer risk. The meta-analysis also found that fermented dairy foods intake was associated with an overall decrease in cancer risk.
Yogurt Consumption and Lung Cancer Risk
In another study published in 2019, the researchers did a pooled analysis which included 10 cohorts including 14,45,850 adults from studies that were conducted in the United States, Europe, and Asia, between November 2017 and February 2019, to evaluate the associations of dietary fiber and yogurt (probiotic food) consumption with lung cancer risk . The analysis included 6,27,988 men, with an average age of 57.9 years and 8,17,862 women, with an average age of 54.8 years. A total of 18,822 incident lung cancer cases were reported during a mean follow-up of 8.6 years. (Jae Jeong Yang et al, JAMA Oncol., 2019)
The study found that both fiber and yogurt (probiotic food) consumption may reduce the risk of lung cancer. The researchers mentioned that the associations of fiber or probiotic yogurt with lung cancer risk were significant in people who never smoked and were consistent across sex and race/ethnicity. It was also found that a high yogurt (probiotic food) consumption by the group with the highest intake of fiber, synergistically resulted in more than 30% reduced risk of lung cancer compared to people with the least intake of fiber who also didn’t consume yogurt.
Yogurt Consumption and the Risk of Colorectal Polyps
Analysis of Data from the Health Professionals Follow-up Study and Nurses’ Health Study
In a study published this year by the researchers from China and the United States, they evaluated the association between yogurt (probiotic food) consumption and the risk of precursors of colorectal cancer. The study used data from 32,606 men in the Health Professionals Follow-up Study (HPFS) and 55,743 women in the Nurses’ Health Study (NHS), who have undergone lower endoscopy between 1986 and 2012. In total, 5811 adenomas in men and 8116 adenomas in women were reported. (Xiaobin Zheng et al, Gut., 2020)
The study found that men who took yogurt twice or more per week may have a 19% reduction in the risk for conventional colorectal polyps and a 26% reduction in risk for serrated polyps. The study also highlighted that this reduction was more significant in colon polyps than rectal polyps. The researchers did not find any association between yogurt consumption and risk of colorectal polyps in women.
Analysis of Data from the Tennessee Colorectal Polyp Study and Johns Hopkins Biofilm Study
Another study published this year by the researchers from the United States also evaluated the association between yogurt (probiotic food) intake and colorectal cancer risk. The study used data from 5446 men in the Tennessee Colorectal Polyp Study and 1061 women in the Johns Hopkins Biofilm Study. (Samara B Rifkin et al, Br J Nutr., 2020)
In the Tennessee Colorectal Polyp Study, the researchers found that, compared to no or rare yogurt consumption, the daily yogurt intake was associated with 46% decrease in hyperplastic polyps (usually do not lead to cancer) and weekly yogurt intake was associated with 27% decrease in adenomatous polyps (have the potential to become cancerous) among women.
In the Johns Hopkins Biofilm Study, the researchers found that weekly yogurt intake and probiotic use were associated with 25% and 28% reduction in overall adenomatous polyps, respectively, in comparison with no use.
Based on this, the analysis concluded that yogurt intake may be associated with decreased risk of hyperplastic and adenomatous polyps, and probiotic use may be associated with a decreased risk of adenomatous polyps. The researchers pointed out the need for more well defined studies to verify these associations.
Probiotics for Preventing Postoperative Infection in Colorectal Cancer Patients
In a meta-analysis published in 2019, the researchers in China evaluated the preventive effect of probiotics on infection after colorectal cancer surgery. The study obtained data through literature search in Pubmed, Embase, Cochrane Library as well as China National Knowledge Infrastructure (CNKI) databases. (Xiaojing Ouyang et al, Int J Colorectal Dis., 2019)
The study found that intake of probiotics may contribute to the reduction of overall infection rate after colorectal surgery. They also found that the incidence of surgical wound infections and pneumonia were also reduced by probiotics. The study suggested that probiotics have potential efficacy on preventing postoperative infection and related complications in cancer patients undergoing colorectal surgery.
Probiotic Supplementation for Diarrhea in Cancer Patients Receiving Radiation Therapy
Study on Cancer Patients Receiving Radiation Therapy
In a study published in the Nutrients Journal in 2019, the researchers from Malaysia did a systematic review to evaluate the protective effects of probiotic supplementation against radiation-induced diarrhea. The primary analysis included 8 trials, with a total of 1116 participants. (Navin Kumar Devaraj et al, Nutrients., 2019)
The study found that compared to those who didn’t take probiotics, the participants who took probiotics were associated with a lower risk of radiation-induced diarrhea. Significant benefits were seen in those patients who received only radiation therapy. However, the study didn’t find significant reduction in radiation-induced diarrhea in patients receiving both radiation therapy and chemotherapy.
The study suggested that the use of probiotics may be beneficial in preventing radiation-induced diarrhea in patients receiving radiotherapy.
Study on Cancer Patients Receiving Chemotherapy or Radiation Therapy
In another study published in 2018, the researchers from Karolinska Institutet in Sweden evaluated the clinical effectiveness and side effects of probiotics used alone or in combination with other agents for prevention or treatment of chemotherapy-related or radiotherapy-related diarrhoea in cancer patients. Data was obtained by searching the Cochrane Central Register of Controlled Trials (CENTRAL; 2017, Issue 7), MEDLINE (1946 to July week 2, 2017) and Embase (1980 to 2017, week 30) databases and from clinical trial registers and reference lists of the studies included. The analysis included 12 studies involving 1554 participants. (Dang Wei et al, Cochrane Database Syst Rev., 2018)
Based on the analysis, the researchers concluded that there was limited evidence supporting the effects of probiotics for prevention and treatment of diarrhoea related to radiotherapy either with or without chemotherapy, or chemotherapy alone. They pointed out that the studies used were underpowered and the information on severe side effects were absent from all studies. The researchers hence suggested more robust evidence/studies based on well-designed trials to confirm the impact of probiotics on radiation/chemotherapy induced diarrhea.
Efficacy and Safety of Probiotics on Cancer Patients
In a study published in 2014, the researchers from Leeds and York in the United Kingdom evaluated the efficacy and safety of probiotics in people with cancer. Data for the analysis was identified through screening multiple databases and grey literature for randomized, controlled trials. 11 studies with 1557 participants were included to evaluate the efficacy and 17 studies with 1530 participants were included to evaluate the safety of probiotics use in cancer patients. (M G Redman et al, Ann Oncol., 2014)
The study found that probiotics may reduce the severity and frequency of diarrhoea in patients with cancer and may also reduce the need for antidiarrheal medication. However, the researchers suggested more studies and evidence to establish these findings. In the safety assessment, it was found that 5 cases showed probiotic-related infections in blood cultures. The researchers concluded that probiotics may be a rare cause of sepsis and further evidence needs to be collated to determine whether probiotics provide a significant overall benefit for people with cancer.
Recently, in 2018, the researchers from Leeds and York in the United Kingdom carried out the analysis again after including more trials. 21 studies with 2982 participants were included to evaluate the efficacy and 25 studies with 2242 participants were included to evaluate the safety of probiotics use in cancer patients. (Hadeel Hassan et al, Support Care Cancer., 2018)
The meta-analysis found that probiotics may reduce the incidence of diarrhoea and the duration of fever in cancer patients, however, further studies are still required. In the safety assessment, it was found that 5 cases showed probiotic-related infections in blood cultures.
Post the re-assessment, the researchers again concluded that the studies needed to assess the true effect of probiotics in cancer patients were still insufficient. They stressed on the need for improved reporting of outcomes and adverse events in clinical trials to improve the accuracy and confidence of conclusions drawn in the meta-analysis.
Different studies suggest that an intake of probiotic foods such as yogurt may help in reducing the risk of specific types of cancer including lung cancer and colorectal polyps. Studies also suggest that probiotic yogurt may be beneficial in alleviating gastrointestinal issues like diarrhea, irritable bowel syndrome, constipation, intestinal gas or bloating. Some studies also found that probiotics use may substantially reduce diarrhea after radiation treatment for cancer and infection rates after colon cancer surgery. However, researchers suggested carrying out more well-designed studies to improve the accuracy and confidence of conclusions drawn in the meta-analyses.
Few studies reported that probiotics may be a rare cause of sepsis especially in those who have a compromised immune function or low white blood cell count. Cancer patients who are undergoing treatment, or on clinical trials with dietary restrictions and those who are candidates for immunotherapy should not take probiotic foods (including yogurt parfait) without consulting their oncologist and nutritionist. Further evidence needs to be collected to determine whether probiotics provide a significant overall benefit for people with cancer.
Cancer patients often have to deal with different chemotherapy side effects which affect their quality of life and look out for alternative therapies for cancer.Taking the right nutrition and supplements based on scientific considerations (avoiding guesswork and random selection) is the best natural remedy for cancer and treatment related side-effects.