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In the 1950’s smoking was the epitome of ‘cool and glamour’. With the extensive knowledge we have gained over the last few decades, we are now wizened to the shadow that smoking casts over our health. Smoking is one of the main causes of lung and heart disease, stroke, and many types of cancer. Tobacco smoke is comprised of more than 7000 chemicals, of which 250 are confirmed to be harmful to both smokers and non-smokers. One of these chemicals is benzene, which damages the DNA and results in mutations.1

While the ideal is for people to stop using tobacco altogether, this is easier said than done in many cases.1 Though the majority of people who smoke actually want to stop, only 30 – 50% of people attempt to quit and most of these people relapse.2 In fact, it is estimated that less than 10% of adult cigarette smokers succeed in quitting each year.1  Furthermore, even though tobacco cessation decreases the occurrence of cancer, risk reduction never returns to baseline.2 

The good news is that a little green powerhouse offers a ray of hope!

It all started with the observation that diets rich in fruits and vegetables reduce the risk of developing cancer and other age-related chronic diseases. Specifically, it was noted that cruciferous vegetables are particularly more protective than many other dietary plants. Cruciferous vegetables consist of Brassica (broccoli, cabbage, and cauliflower), and Raphanus (radish and daikon). Brassica vegetables are rich in glucoraphanin, which largely accounts for their protective properties, and their consumption is associated with more than 40% lower risk of lung cancer among smokers.3 

Glucoraphanin is converted to the phytochemical (plant chemical) sulforaphane by the plant enzyme myrosinase.2,3 Sulforaphane enhances the detoxification of benzene, aldehydes, and polycyclic aromatic hydrocarbons found in tobacco smoke and air pollution, through the conversion of a damaging chemical into something more benign.1,2 Otherwise healthy smokers have an increased ability to detoxify tobacco carcinogens through the consumption of sulforaphane.1 

So, the million-dollar question is, how much do we have to eat to get the health benefits seen in clinical trials?

Nature likes to keep us on our toes, and the glucoraphanin content of Brassica vegetables ranges depending on where it is grown and environmental exposures.2 On average, approximately 840 g of mature broccoli contains the amount of glucoraphanin that provided the benefits seen in the study by Baumann et al. (2022). This is a relatively large amount of broccoli that needs to be consumed daily, and broccoli sprouts may be a more practical food option as they contain 10 – 100 times the level of glucoraphanin as mature plants and they are also a rich source of myrosinase activity. 2,4 Thus, only 8 – 84 g of broccoli sprouts are needed as opposed to 840 g of mature broccoli. ‘Stressing’ the food through food preparation, such as freezing, or chewing further increases the release of sulforaphane.2 Freezing broccoli sprouts and then preparing them in a smoothie can assist with maximising the delivery of sulforaphane in smaller quantities. The inclusion of a source of vitamin C is also important for the activation of myrosinase.

However, not everyone may have the time (or patience) to prepare broccoli sprouts, and supplements containing the bioactive components in cruciferous vegetables may be a more practical way of delivering predictable and desired concentrations.2  It is also important to note that the gut microbiota in humans contributes to the conversion of glucoraphanin to sulforaphane. The conversion appears to be higher during the day, compared to the night, and this may need to be considered when planning the timing of consumption of sources of glucoraphanin.