Research suggests that a healthy gut microbial environment influences overall health. The amount, diversity, and type of beneficial microorganisms in the gut microbiome may promote gastrointestinal health, immune health, energy metabolism, digestion, and vitamin synthesis. Broccoli, a cruciferous vegetable, contains dietary fibers and phytonutrients that may enhance the production and proliferation of beneficial bacteria. Broccoli contains glucosinolate phytonutrients that the microbiome can metabolize into bioactive isothiocyanates. The isothiocyanates have been shown to support a healthy immune system and attenuate the adverse effects of diverse pathologies.  

Kaczmarek and colleagues conducted a controlled feeding, randomized, crossover study in healthy adults (n = 18) with two 18-day treatment periods separated by a 24-day washout period. In the intervention period, the adults were fed 200 g of cooked broccoli and 20 g of raw daikon radish per day. Compared to the relative controls, the individuals in the broccoli group displayed increased function of the endocrine system, transport and catabolism, and energy metabolism. Moreover, the broccoli group exhibited a decreased relative abundance of Firmicutes by 9% and an increased relative abundance of Bacteroidetes by 10% and Bacteroides by 8%. The effects were most potent in participants with a body mass index greater than 26 kg/m². A higher value of the Bacteroidetes to Firmicutes ratio that resulted in this experiment has been shown to promote healthy body weight in certain studies. 

The antimicrobial properties of broccoli have been reported in various publications. An in vitro disease model determined that broccoli sprouts have antibacterial activity against Gram-positive bacteria (Staphylococcus aureus and Bacillus subtilis) and Gram-negative bacteria (Salmonella typhimurium and Escherichia coli). Gram-positive bacteria were more sensitive to broccoli sprout extract than gram-negative bacteria. In vitro, animal, and human clinical studies using broccoli sprout administration demonstrate the attenuation of H. Pylori infection due to the high sulforaphane content of broccoli sprouts. One clinical study showed that a high-Brassica diet (including broccoli) might reduce the relative abundance of sulfur-reducing bacteria associated with ulcerative colitis and irritable bowel syndrome. 

In a randomized, double-blind, controlled trial, patients with H. pylori infection without atrophic gastritis (n = 110) were administered a placebo or broccoli seed extract supplementation for 2 months. Compared to the placebo, the individuals receiving the broccoli seed extract supplementation displayed a higher rate of H. Pylori eradication, reduced risk of gastric mucosal lesions, and reduced inflammatory cytokines, including interleukin-8, interferon-gamma, pepsinogen (PG) I, PG I/PG II ratio, and gastrin-17.

The glucosinolate polyphenols in broccoli may be clinically relevant in supporting overall gastrointestinal health. Research indicates that dietary broccoli, broccoli sprouts, or broccoli seed extract supplementation may promote a healthy gut microbial environment. 

By Danielle Moyer, MS, CNS, LDN