Yakult study calls for further probiotic research on aflatoxin toxicity
Aflatoxin is a fungal toxin found in many foods such as nuts, cereals, spices and herbs. Chronic aflatoxin exposure has been linked to hepatocellular carcinoma (liver cancer) and the International Agency for Research on Cancer (IARC) classifies aflatoxin as a group one agent that is carcinogenic to humans.
A 2010 risk assessment study suggested aflatoxin plays a causative role in 4.6–28.2% of all global liver cancer cases.
Research from the University of Georgia in the US and the Universiti Putra Malaysia has now asked whether probiotics could be used as a strategy against this.
Prompted by previous in vitro and in vivo animal studies that demonstrated the detoxification ability of probiotics, the authors hypothesised that probiotics would bind to aflatoxins forming an aflatoxin–bacteria complex which is excreted in the faeces.
This would prevent the aflatoxin being absorbed through the intestinal wall and posing a health risk.
The strain used was Lactobacillus casei Shirota (LcS), which features in Yakult's probiotics drinks.
Developing countries such as Africa and Asia have a particularly high prevalence of aflatoxin in foodstuffs, and although many countries have imposed strict regulations, it is believed that some contaminated foods still exist in the human supply.
Dietary or clinical interventions to reduce the bioavailability of aflatoxin in the human body are a secondary prevention step, and the scientists in this study were looking at practical alternatives to current non-nutritional absorbents such as clay.
Scientists conducted a randomised, double-blind, cross-over, placebo-controlled study with two four-week intervention phases.
A total of 71 aflatoxin-exposed subjects were divided into two groups either receiving Yakult probiotic drinks twice a day or placebo drinks. Blood and urine samples were collected, then after a two week washout period the two groups were swapped over and samples were collected again.
The results showed significant reduction in serum biomarkers for aflatoxin in some subjects when a within group analysis was done, although the overall results for intervention were not significant during the four weeks.
The authors said: “Overall, the intervention did not change both aflatoxin biomarkers’ concentrations but the concentrations were reduced in certain subjects who participated in this study.”
Increased energy intakes
Apart from added LcS, the probiotic and placebo drinks had identical ingredients - fructose, maltitol, skimmed milk powder, glucose and permitted flavouring.
The subjects’ energy intake increased from baseline in both groups:“The energy intake was significantly higher at the last week of intervention, which saw an increase of 16·4% energy intake from 7937 kJ (1897 kcal) to 9247 kJ (2210 kcal). Regarding macronutrient intakes, the intakes of carbohydrates and fat were significantly higher compared with the 6th week intakes.”
The authors noted that controlling the diet of subjects during intervention was a challenge and financial restrictions meant study times weren’t long enough.
Previous in vitro and animal studies found varying results using probiotics to fight aflatoxins, but the strains used and the biomarkers of aflatoxin tested influenced this.
Previous studies have also suggested that probiotic consumption is not fast-acting, but rather acts over a longer period of time not addressed in this four-week study.
The authors discussed the influence of the subjects’ diet during the study period, considering aflatoxin exposure through food and how macronutrient ratios can have varying effects on detoxification processes and survival of LcS.
They recommended further studies over longer periods of time, using faecal analysis and looking at dietary effect using in vitro and in vivo models.
“Based on these findings, a longer intervention study is warranted to investigate the effects of continuous LcS consumption to prevent dietary aflatoxin exposure”
Source: British Journal of Nutrition
Published online ahead of print, doi:10.1017/S0007114515004109
“Effect of supplementation of fermented milk drink containing probiotic Lactobacillus casei Shirota on the concentrations of aflatoxin biomarkers among employees of Universiti Putra Malaysia: a randomised, double-blind, cross-over, placebo-controlled study”
Authors: Sabran Mohd Redzwan et al.