Re: bitter tasting fruit for vagus nerve stimulation?

 Dragon fruit, paw paw, currents, cranberries, kumquat, bitter melon and tamarillo all have some bitter components. There are also some bitter species of gooseberry. Grapes can also have a bitter taste due to the tannins in their skins.  And many fruits have bitter peels such as oranges and bananas. Although with all the herbicides and pesticides these days you have to be a lot more careful about fruit peels.

You will also find a number of bitters in non-fruit plants such as dandelion leaves and some lettuces.