Cooking goes off the boil

It’s always been your mum’s favourite way to cook the veg, but maybe boiling them to a pulp isn’t the best for your health.

If you like your broccoli with added anti-carcinogenic properties - better not boil them!

The anti-carcinogenic properties of Brassica vegetables such as broccoli, Brussel sprouts, cauliflower and green cabbage are fairly well known, but now researchers think that overcooking them in boiling water destroys their anticancer properties.

Professor Thornalley of the Warwick Medical School, and one of the researchers on the study said: “If you want to get the maximum benefit from your five portions-a-day vegetable consumption, and you are cooking your vegetables then boiling is out. You need to consider stir frying, steaming or micro-waving them.”

Past studies have shown that the anti-carcinogenic effects of these vegetables come from the high content of substances known as glucosinolates which are metabolised to cancer-preventive substances known as isothiocyanates.

After the effect of cooking on the glucosinolate content of vegetables by boiling, steaming, microwave cooking and stir-fry was examined the researchers found that boiling reduced the chemical the most. In fact after boiling for 30 minutes, 77% of the glucosinolate content in broccoli was lost. The other methods gave no significant loss of total glucosinolate content.

While this may change our cooking habits – the way we store vegetables looks safe. The team found that storage of the vegetables at ambient temperature and in a domestic refrigerator showed no reduction of glucosinolate levels with only minor loss after 7 days.