Originally Posted by hunter_la5
The amount of cyanide contained in a seed is negligible. We're talking trace amounts. There was a big media scare years back about trace amounts from seeds allegedly being detected in commercial apple juice, but it turned out to be much ado about nothing. You have nothing to worry about.
True, they won't hurt you but there could be a flavor impact. I'd core any apples before juicing for that reason. Grapes, too, or any seeded fruit that has a seed that doesn't taste great would be something that I'd avoid crushing in the juice.