Broccoli! The bitter brassica delivering a sweet health reward

Broccoli, love it or hate it, is well-known as a food that has a host of vitamins, minerals and fibre beneficial to our health in general. Evidence is mounting too that it may have properties to help fight cancer, boost immunity, counter inflammation and even help children with autism.

A team led by Dr Tom Karagiannis from Monash University’s Department of Diabetes has published a review of clinical trials worldwide testing the benefits of the active ingredient sulforaphane. Sulforaphane is produced in the body from a naturally occurring compound called glucoraphanin, found in cruciferous vegetables including cauliflower, cabbage, bok choy and broccoli. The highest concentration is found in broccoli sprouts.

“We looked at more than 100 clinical trials done into sulforaphane and how effective it was in different types of disease,” Dr Karagiannis said. “In the last couple of years, research has increased exponentially on this compound,” he said.

The review, published in Clinical Nutrition last month, is part of a body of work by Dr Karagiannis with the ultimate aim of developing a pharmaceutical-grade sulforaphane preparation for clinical use in inflammatory conditions.

Sulforaphane has been studied extensively for its immediate and long-term health benefits, particularly in the context of cardiovascular disease and cancer, it said.

The compound was first identified in the early 1990s by researchers at Johns Hopkins University in the US. Early research focussed on sulforaphane as a chemopreventive (a compound which inhibits cancer initiation or progression); it was widely investigated in breast cancer. Relatively recent studies showed sulforaphane had beneficial effects in autism spectrum disorder and schizophrenia.

“Some of the latest research is very exciting,” Dr Karagiannis said. “It showed sulforaphane improved the behaviourial patterns of children with autism spectrum disorder over time – they had better memory and were able to focus better.”

The review focussed on sulforaphane’s impact on diseases based on chronic inflammation such as asthma and allergic airways disease, an area in which Dr Karagiannis and colleagues have worked for a number of years.

Studies they have conducted injecting pure compound in mouse models of allergic airways disease, which mimics asthma, showed sulforaphane had remarkable beneficial effects, he said.

“Sulforaphane appears to be working in our asthma models by four mechanisms: antioxidant effects mediated by a major antioxidant pathway called the Nrf2 pathway; anti-inflammatory effects; genetic and epigenetic effects, and direct actions causing opening of the airways of the lungs,” he said.

“The major issue is trying to get the right concentration of the active compound  – we don’t know exactly how to administer it at this time.”

Dr Karagiannis said that while clinical studies have demonstrated the benefits of sulforaphane in breast cancer for 20 years, with some cancer centres conducting surveys about how much broccoli patients consumed, that eating broccoli was not recommended clinical practice. “Patients should keep to their usual prescriptions,” he said.

The review concluded that clinical studies had yielded promising yet inconsistent results, largely due to differences in the study designs, source and dose of the compound, and the context of the disease and/or target population studied. Nevertheless, the beneficial effects observed in certain diseases and the lack of serious side-effects observed to date is exciting, it said.

Dr Karagiannis is preparing to conduct a clinical trial into asthma using a supplement made of broccoli powder extract his team has had made.

He heads the Epigenomic Medicine laboratory and and is Principal Investigator of the McCord Research Group in Melbourne, Australia, which funds his research. He collaborates on sulforaphane studies with Central Clinical School scientist Dr Simon Royce and Associate Professor Paul Licciardi from Murdoch Children's Research Institute.

First author on the paper was PhD student Nadia Mazarakis.

Mazarakis N, Snibson K, Licciardi PV, Karagiannis TC. The potential use of l-sulforaphane for the treatment of chronic inflammatory diseases: A review of the clinical evidence. Clin Nutr. 2019 Mar 25. pii: S0261-5614(19)30136-0. doi: 10.1016/j.clnu.2019.03.022. [Epub ahead of print]