The vegetable contains a compound known as sulforaphane, which previous studies suggest helps to maintain people’s blood sugar levels and may even have anti-cancer properties.

Yet, sulforaphane’s benefits are destroyed within minutes of cooking and require broccoli to be ‘damaged’ before they can be absorbed.

A Chinese study suggests chopping the vegetable into 2mm pieces and letting them ‘sit’ for 90 minutes before gently stir-frying increases their sulforaphane levels by 2.8 times.

Although unclear exactly why this occurs, the researchers believe waiting before cooking chopped broccoli may allow sulforaphane to ‘develop’.

While such preparation may seem like a lot of trouble, past research suggests it may be worth the effort as sulforaphane is poorly absorbed when taken as a supplement.

Chopping broccoli into 2mm pieces and letting it sit may be the healthiest way to eat it

How the research was carried out     

The researchers, from Zhejiang University, bought several heads of broccoli from a local market.

The broccoli was chopped to activate the enzyme myrosinase, which plants have evolved to protect themselves against herbivores.

Myrosinase causes sulforaphane to become available for absorption.

The pulverised broccoli was then divided into three groups.

Some of was left as it was, some was immediately stir-fried for four minutes and the remainder sat for 90 minutes before also being cooked quickly over a high heat.

Waiting for 30 minutes may be sufficient  

Although untested, the researchers believe 30 minutes may be a sufficient amount of time to allow raw, chopped broccoli to sit in order to ensure maximum sulforaphane absorption.

They are also investigating how to make the most of the vegetable’s nutritional benefits without having to do so much preparation.

The findings were published in the Journal of Agricultural and Food Chemistry.

How else does broccoli boost health? 

According to research released in October last year, a daily dose of broccoli could prevent everything from arthritis to heart disease by keeping your gut healthy.

Mice fed a diet supplemented with broccoli are better able to tolerate digestive issues, a study found.

This is thought to be due to cruciferous vegetables, such as cauliflower and kale, containing a substance that promotes gut health and barrier function, according to the researchers.

Maintaining a healthy intestinal lining could prevent leaky gut syndrome, which exposes the body to toxins and pathogens, they add.

Lead author Professor Gary Perdew from Penn State University, said: ‘There are a lot of reasons we want to explore helping with gastrointestinal health and one reason is if you have problems, like a leaky gut, and start to suffer inflammation, that may then lead to other conditions, like arthritis and heart disease.’