Y: Mmm, there's nothing like a fresh slice of watermelon. But, oops, I just swallowed a seed! That's the fifth one today.
D: Isn't that what you're NOT supposed to do? I thought watermelon seeds weren't edible. I always spit them out.
Y: Well, I didn't want to spit in the studio! Anyway, a few seeds from fruits such as watermelons or apples passing through your digestive tract won't hurt you. But they won't help you much either. Nutritionally, there just isn't much in a seed that your body wants. The worst a seed could do is block your intestine or airway, but that's really rare.
D: Wait, don't some seeds contain dangerous chemicals? What about the cyanide I've always heard is in apple seeds?
Y: There's some truth to that. Apples, cherries, almonds, and peaches all have seeds or pits that contain a bit of the chemical amygdalin, which can be converted to cyanide by the bacteria natural to the intestinal tract. But it's still such a small amount that you probably wouldn't get sick. Also, seeds don't stay in your body long. We're talking twenty to thirty hours to make it through your digestive system, tops. So swallow away! Or at least don't worry about it if a seed accidentally slips down your throat.
D: Well, I guess I won't sweat it if I do swallow one. But I still plan to spit out watermelon seeds!
Y: Wanna have a seed-spitting contest?