In the big scheme of things it doesn't matter whether you swallow fruit seeds or not. Besides nourishing our bodies, one of the primary reasons we frugivores eat fruit is to disperse the seeds so the tree or vine will have a better chance of propagating. This will be accomplished whether we spit or sh*t the seeds.
Personally, however, I don't think it's a good idea to eat seeds. To me it doesn't feel right to swallow small hard things without chewing them -- although I donít necessarily make a point of never doing it (the random seed is always going to get through), and the act of chewing grape, apple or orange seeds doesn't feel pleasurable to me. And since we get all that we need from the sweet and pleasure-giving parts of the fruit, it makes no sense to deliberately eat seeds in order to get the "extra" nutrients. Adequacy is all our bodies require. Any more than that is a burden. In addition, although eating seeds without chewing doesn't hurt a plant's chances for reproduction, chewing them certainly does because seeds that are destroyed cannot serve their primary purpose in nature -- reproduction.
All the fruits that we eat today have been hybridized for various practical reasons including marketability, transportability, shelf life and others. It's virtually impossible to live a normal life and not have to resort to eating hybridized fruit, if a person wants to enjoy the highest levels of health (since fruit eating is necessary for that). For better or worse, fruit producers have made it possible to ship fruit to all corners of the earth. If you've ever eaten a wild apricot, for example, you'll know how juicy, tender and delicious they are. Those are fine qualities when it comes to nurturing a human body but their fragile nature makes it impossible to get them to market. With the apricot, as with so many other fruits, it was necessary to change them so they could handle the rigors of the modern food distribution system. Some fruits have come through this process better than others. I'd rather not consume apricots at all than eat what passes for them in supermarkets. The same goes for strawberries and raspberries.
I do enjoy seedless grapes, however. Iíve found a small organic farm in Eastern Washington that grows the best grapes I've ever tasted and every year I go over and harvest some 300 pounds of them for my consumption and that of my fellow raw fooders here in Seattle. There was a time earlier in my transition when I was not able to eat seedless grapes because I noticed slight symptoms and I still get them when I eat too many of the green varieties (red and purple ones donít have the same effect); also I do still avoid seedless watermelon, because I don't like the way it makes me feel.
Since fruit's very purpose is propagation, obviously it should always have seeds! When a plant is manipulated to produce fruit without seeds, the fruit is obviously going to be lacking its natural balance. The space that seeds normally occupy in the fruit are taken up by something else, and we end up getting too much of one thing and not enough of something else. However, we can't go around taking supplemental grape seed oils or extracts when we eat seedless grapes, hoping to make up the difference, because the truth is we simply don't know what we're missing or getting too much of. And whatever it is, if we don't eat it in its natural context it won't be usable.
I would hasten to add, however, that even though seedless fruit is not 100% naturally balanced, it is a million times better than just about any other food category you could mention. Eating seedless fruit is a burden that the body can handle, especially people who are transitioning away from the standard way of eating.