Probiotics can protect against colorectal cancer, but not everyone may benefit: Japanese population study
Researchers at Fukushima Medical University sought to explore the effects of yogurt containing Bifidobacterium longum (BB536-y) and fructo-oligosaccharides in preventing colorectal carcinogenesis in healthy subjects.
Cooperating against cancer
They recruited 27 healthy adults (aged 60 on average) and divided them into two groups: one was given a yogurt containing only the probiotic strain, while the other was given a yogurt containing both the probiotic strain and fructo-oligosaccharides.
Each participant took the yogurt once daily for five weeks, and their faecal samples were collected before and after yogurt intake, so the researchers could analyse the amount of short-chain fatty acids (SCFAs) present.
They also assessed the profile of each participant’s intestinal flora, such as putrefactive bacteria and enterotoxigenic Bacteroides fragilis (ETBF), which are said to be risk factors for colorectal carcinogenesis.
Subsequently, they reported that consumption of the yogurt containing BB536-y raised the total amount of SCFAs in the subjects’ faeces, and “significantly suppressed” the growth of putrefactive bacteria and detection rate of ETBF.
When it came to intake of the yogurt containing both BB536-y and fructo-oligosaccharides, the researchers observed a higher Bifidobacterium detection rate than that of just BB536-y.
This meant that the ingestion of functional foods such as probiotics and prebiotics could help to inhibit carcinogenesis in the colon and in turn, lower the risk of colorectal cancer.
Another mechanism of probiotic intake on cancer risk was its conversion of intestinal content pH to within an acidotic pH range, which led to the suppression of putrefactive bacteria growth, and increased SCFA production in the intestines.
Cellular activity
The researchers also investigated the preventative effects of SCFAs — whose production was “enhanced by intake BB536-y and fructo-oligosaccharides” — on human colon cancer cell lines cultured within butyric, isobutyric and acetic acids, in order to assess the their effects on cancer cell growth.
They found that the SCFAs exhibited significant inhibitory action against cancer cell growth, especially butyric acid. This was followed by isobutyric acid, then acetic acid.
The researchers wrote that these findings suggested that the intake of BB536-y alone, as well as combined supplementation of both BB536-y and fructo-oligosaccharides, could prevent colorectal carcinogenesis.
The anti-cancer effects of probiotics have been extensively studied, either on their own or in combination with certain foods and ingredients.
An NUS study reported that a combination of a probiotic and broccoli extract killed colorectal cancer cells, while Professor Luis Vitetta from the University of Sydney said at last year’s Probiota Asia that probiotics could help to lower cancer risk via gut microbiome modulation.
He added that for cancer patients, probiotics could be used as adjunctive medicines to reduce toxicity from cancer treatments such as radiotherapy by improving intestinal barrier function.
Noting the differences
Despite the generally positive findings of the current study, however, the researchers also wrote: “The important issue of human enteric bacterial flora varying among individuals needs to be borne in mind in the context of the results of this study.”
They said these differences could be attributed to differences in intestinal commensal bacterial species, which utilise organic acid.
Probiotics are involved in the production of SCFAs, whereby lactic acid in the intestinal tract interacts with these bacterial species, and this leads to differences in the compositions of the SCFAs produced.
As a result, the impact of functional foods, such as prebiotcs, probiotics and synbiotics (a combination of the two), will eventually vary among individuals, which poses a “major problem” in the clinical application of such foods.
The researchers concluded: “Major bacterial species currently used as probiotics are species of Bifidobacterium and Lactobacillus.
“Many problems remain to be resolved, in relation to future clinical application of probiotics, and conducting large-scale clinical trials, examination of the behaviour of probiotics in the intestinal tract, and identification of intestinal commensal bacteria that produce SCFAs via commensalism with particular probiotic bacterial species are needed.
“Also, the development of new sparingly digestible saccharides (prebiotics) involved in probiotic bacterial growth, and of probiotic bacterial species and synbiotics is needed.
“We believe that the present report will undoubtedly serve as a foundation for the development of new strategies for preventing colorectal carcinogenesis.”
Source: Euroasian Journal of Hepato-Gastroenterology
https://dx.doi.org/10.5005%2Fjp-journals-10018-1251
“Intake of Bifidobacterium longum and Fructooligosaccharides prevents Colorectal Carcinogenesis”
Authors: Tadashi Ohara, Tatsuo Suzutani
