Eating plenty of red onions could prevent cancer , according to new research.
The vegetable, popular in salads and salsas, is rich in chemicals that destroy tumour cells, say scientists.
And the discovery may soon lead to an anti-cancer pill based on the food’s magical properties.
It is known people with the highest consumption of onions have a lower risk of many types of the disease – including ovarian, bowel and breast cancer .
They contain several anti-cancer compounds including quercetin and anthocyanins – which, crucially, give the red variety their colour.
Abdulmonem Murayyan, a PhD student at the University of Guelph in Canada, said: “Anthocyanin is instrumental in providing colour to fruits and vegetables.
“So it makes sense the red onions, which are darkest in colour, would have the most cancer fighting power.”
In the first study of its kind Mr Murayyan and engineering Professor Suresh Neethirajan found red onions have the strongest cancer fighting power.
The vegetable has been used in mediterranean cooking for thousands of years, which could help explain lower rates of the disease in southern Europe.
Diced in a side salad, sprinkled as a garnish or chopped through a pasta dish, they may just be one of the best raw ingredients you can eat.
Red onions have also been linked with protecting against diabetes and heart disease .
The researchers said onions as a superfood are still not well known, despite containing one of the highest concentrations of quercetin, a type of flavonoid.
But not all are created equal because the red onion not only has high levels of this but also large amounts of anthocyanin, which boosts the scavenging properties of quercetin, explained Mr Murayyan.
Along with Prof Neethirajan, he tested five onion types grown in Ontario and discovered the Ruby Ring red came out on top.
In lab experiments reported in Food Research International, colon cancer cells were placed in direct contact with quercetin extracted from the five different onion varieties.
Mr Murayyan said: “We found onions are excellent at killing cancer cells. Onions activate pathways that encourage cancer cells to undergo cell death.