We’re talking about the media favourite: “Can [Insert food of choice] cure cancer?” or alternatives such as: “Does X cause cancer?” and “Can X prevent cancer?” which seem to pop up in the press every few weeks. This week we focus on broccoli.

Friday 5 December 2014      Research blog
Broccoli and cancer - what's the story?

There are some things in life which you could easily set your watch by.  One of them happens to be a painful annoyance to anyone with a vested interest in evidence-based medicine.  We’re talking about the media favourite: “Can [Insert food of choice] cure cancer?” or alternatives such as: “Does X cause cancer?” and “Can X prevent cancer?” which seem to pop up in the press every few weeks.

Could broccoli fight cancer?

We spotted a classic “click bait” headline in today’s press asking the question: “Could broccoli fight cancer?”  Spoiler alert: No.  There is no evidence that eating broccoli can fight cancer.

The headline is a bit of a trap though because the real story here is that a chemical found in broccoli has been used to develop a drug molecule which plans to be tested in breast cancer patients.  The chemical is called sulforaphane and studies have shown that in its natural form it’s capable of killing cancer cells in laboratory experiments.  But then again so can water, salt, sausage meat, time and even handguns.  These in vitro experiments inform science, but until any anti-cancer activity is demonstrated in animals and humans, we should assume that scientists haven’t yet stumbled on the “cure”’ for cancer.

Cancer drugs derived from natural products

This in no way means that chemicals from plants, vegetables or even sea sponges don’t have the potential to be therapeutic.  In fact, the vast majority of drugs used to treat cancer today are derived from natural products.  The key thing is that scientists have to work out how to extract the active chemical and then find out the best way to use it for medicinal purposes.  In many cases this involves creating a synthetic version which is therapeutically superior to the original molecule.

This is precisely the case for sulforaphane.  Evgen, who earlier this week announced that they are floating the company on the stock exchange to raise the funds for a breast cancer trial, have created a synthetic version of sulforaphane which could be taken as a pill to treat cancer.  And there are very good reasons why this compound needs to be “manufactured”, rather than obtained by force-feeding people broccoli.

Therapeutic chemicals from dietary sources struggle with the problem of bioavailability.  This refers to how much of an administered drug actually reaches a patient’s circulatory system where it has the potential to end up somewhere useful – like a tumour, for example.  Sulforaphane as it exists in broccoli has a very poor bioavailability, meaning that you would have to eat an impossibly large amount of broccoli to even come close to a pharmacologically sensible dose.  The other problem with “natural” sulforaphane is that it’s incredibly unstable.  This means that when eating that tender stem of broccoli, much of the sulforaphane is likely to be rendered useless before it even reaches the blood stream.

Death by broccoli

We also need to be able to monitor how much of a drug is received by a patient by administering it in a pure form as a pill or injection.  It just wouldn’t be possible to measure a dosage if people in hospital were eating plates of broccoli with widely varied levels of sulforaphane.  In fact, there is a danger that things could go the other way and a patient overdoses.  Death by broccoli would probably not be the best way to go.

Lots of research has taken place to make sulforaphane more stable and to increase its bioavailability, which is exactly what Evgen claim to have done.  They have made enough progress now that they want to start a clinical trial of their drug in 50 breast cancer patients.  This is how science works and how many drugs are, and have been, developed for diseases such as cancer.  Nature has gifted us with a vast, diverse range of chemicals which we can exploit but human ingenuity is needed to turn these into viable medicines.

So yes, a chemical which happens to be found in broccoli has the potential to treat cancer, but eating the stuff probably won’t do anything.  Anyway, sulforaphane is also found in Brussels sprouts, and, as it’s nearly Christmas, you’re probably better off stuffing your face with those instead (Disclaimer: Please don’t do this for any other reason than a festive love of sprouts).

Dr Matthew Lam is Breakthrough Breast Cancer's Senior Research Officer