Diana O'Carroll put this question to John Fry, a consultant in food science...

John - Well, it could be but only under rather extreme circumstances. Apple seeds contain a substance called amygdalin that can release cyanide under the right circumstances such as contact with digestive enzymes. The cyanide is linked to sugars in the form of a cyanogenic glycoside and these cyanide-releasing compounds are remarkably common in nature. They occur in more than 2,000 plant species, some of them important foods like cassava. They also crop up in stone fruits like plums, peaches, apricots, and famously, bitter almonds. It's often said that cyanide smells of bitter almonds, but actually, it's the other way around; bitter almonds smell of cyanide.

You need about 1 milligram of cyanide per kilo of body weight to kill a human being. Apple seeds contain about 700 milligrams of cyanide per kilo, so about 100 grams of apple seeds should be enough to dispatch a 70-kg adult human, but that's an awful lot of apple cores even if you don't eat the rest of the apple first. In addition, the seeds would have to be pretty finely crushed to let the enzymes get to the amygdalin at all. All in all, you're safe eating the occasional apple core. I've done it for years. Just don't try eating a bowl of freshly crushed apple pips.

Diana - If a seed weighs 0.7 grams, then you'd need to munch your way through 143 seeds. Apples can contain anywhere between 2 and 20 pips, but a typical supermarket apple will contain about 8. So you'd have to eat about 18 apple cores in one sitting!