12 January - 20 June 2016

Broccoli may help promote a healthy gut

A study by researchers from the Pennsylvania State University, published in the Journal of Functional Foods, has investigated the effects of broccoli on the gut and found that consumption alters the microbial community and helps protect the intestines from toxins.

A study by researchers from the Pennsylvania State University, published in the Journal of Functional Foods, has investigated the effects of broccoli on the gut and found that consumption alters the microbial community and helps protect the intestines from toxins.

Cruciferous vegetables, such as broccoli, cabbage and Brussels sprouts, which are high in vitamins, minerals and fibre have been found in previous studies to be associated with a decreased incidence of cancer. The authors of the current study, Perdew et al., note that one type of nutritional phytochemical present in broccoli, namely glucosinolates, metabolises in the stomach to indolocarbazole (ICZ), known to be an activator of a receptor found in the gut called aryl hydrocarbon receptor (AHR).  AHR has previously been shown to help maintain intestinal balance and help protect against external chemicals and toxins.

In the study, Perdew et al. used mice that had been genetically modified to have either a high- or low-affinity to activation of AHR. Initially, the researchers fed high-affinity mice broccoli at 0% and 10% of diet by weight for seven days. They assessed AHR activation by the amount of Cyp1a1 expressed in the duodenum and found that, relative to the control, the broccoli-fed mice showed a 3-fold elevation in expression while 15% broccoli resulted in a 15-fold increase in Cyp1a1. Perdew et al then used both high- and low-affinity mice and fed them either a control or 15% broccoli diet for 24 days. They discovered that AHR activation, again as measured by duodenum Cyp1a1 expression, was increased by 15-fold for the high-affinity mice and 85-fold for the low-affinity mice relative to the controls and that high-affinity mice expressed a 9-fold higher level than low affinity mice. They note that there was no significant change in weight for the broccoli-fed mice, relative to controls. 

Perdew et al. note that as whole broccoli consumption has been shown to alter "the resident microflora in mice", they wanted to “assess the combinatorial impact of AHR status and consumption of broccoli upon microbial community structure”. To this end, cecal microbial population profiles were obtained from both mice types after 24 days of consumption. The study indicates that it demonstrated "significant differences" in microbial community and states that the mice on the broccoli diet showed "decreased prevalence of bacterial species associated with Crohn’s Disease".

The AHR has been shown to play a role in reducing the severity of disease associated with chemically induced colitis. Perdew et al. therefore gave both mice types either a control or 15% broccoli diet for 14 days before adding a chemical to their drinking water for 6 days to induce colitis. The study found that high-affinity mice on a control diet showed "marked decreases in body weight" after four days of the chemical. The high-affinity mice on the broccoli diet however lost much less weight, showing only 5% loss at the end of the 6 days compared to an average of 12% for the other three groups. Other indicators of colitis were also reduced in the broccoli-fed mice.

In conclusion, Perdew et al. state that they showed that broccoli mediated benefits in high- and low- affinity mice with a greater benefit in high-affinity mice, and at doses between 15 and 60 times lower than previously shown. They reiterate that broccoli consumption alters microbial community structure, which may improve host intestinal inflammatory status, and that AHR activation mediated by broccoli consumption helps mitigate chemically-induced colitis.

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