Some people do not tolerate high acid foods very well, and generally try to avoid moderately acidic foods as well. This can create problems. Since it can be hard to know which foods are acidic, which are alkaline, and which are neutral.
Some foods are well know, such as lemons. Everyone knows that lemons are acidic.
But what about raspberries? Are raspberries acidic?
The answer is that yes, raspberries are acidic, but only slightly so. The sources I can find seem to suggest that the pH level of raspberries is around 6 or so, which places them not far from the completely neutral level of 7.
If you do not tolerate acidic foods, you should be alright with raspberries, so long as they are eaten in moderation.