Leaving chopped vegetables on the counter for ten minutes before cooking them could reduce your risk of heart disease, according to diet guru Professor Tim Spector.

The scientist, who co-founded the popular diet app ZOE, urged Britons to let their chopped onion and garlic sit before throwing it in the pan - as this boosts levels of a chemical that can reduce cholesterol and stabilise blood sugar.

In an article offering his top diet tips for 2025, Prof Spector wrote: 'Onion and garlic, as well as cabbage and broccoli, are good sources of sulforaphane, a chemical that has been shown to improve glucose control and cholesterol levels.'

He told The i that cooking destroys an enzyme in the vegetables called mirosinase, from which sulforaphane derives. 

'But if you let your vegetables sit for five to ten minutes before cooking them, the sulforaphane is activated and survives the cooking process.'

Cholesterol is a fatty substance vital for the normal functioning of the body.

But too much of it can cause a build-up in the arteries, restricting blood flow to the heart, brain and rest of the body - raising the risk of angina, heart attacks, strokes and blood clots.

High cholesterol is a major risk factor for heart disease, one of the biggest killers in the UK and US.

High levels are mainly caused by eating fatty food, not exercising enough, being overweight, smoking and drinking alcohol - but it can also run in families.

Prof Spector has previously spoken of the dangers of frequent blood-sugar spikes, said to be linked to obesity due to its destabilising effect on our hunger levels.

The vegetable trick is not the only tip Prof Spector highlighted in his rundown of diet advice.

He also suggested cooking tomatoes with extra-virgin olive oil to extract more nutrients from them, as well as swapping ultra-processed stock cubes for miso paste made from fermented soya beans, which are said to benefit the trillions of healthy microbes in our gut.

He also urged Britons to incorporate more fermented food in their diet, such as kimchi - a Korean dish made of fermented cabbage.

The expert in genetic epidemiology at King’s College London also touted the benefits of using vinegar in salad dressings. 

The acidity of the liquid, he said, has been shown to help stabilise blood-sugar levels, reducing the chance you'll develop hunger pangs and snack between meals. 

Starting every meal with a small salad is a good tip too.

'There is emerging evidence that eating salads or other vegetables as starters ten minutes or so before you have a carbohydrate-rich meal can help to keep you fuller for longer and reduce blood sugar spikes from the starchy food,' wrote Prof Spector.

Heart and circulatory diseases lead to 160,000 deaths each year in Britain – an average of 460 fatalities a day.

The US death toll is even higher, with heart disease killing 659,000 people each year.