I was wondering, I eat a lot of tomatoes since I love them. I'd say between 5 to 8 a day. Could this be harmful or result in any side effects? I hear they contain a large amount of vitamin A, which can be harmful in some cases?
No, vitamin A present in tomatoes is not harmful, as it's not Retinol, which is Vitamin A issued from animal produce. Tomatoes however are from the nightshade family and some might develop allergies over that; so one should listen carefully for signs of such allergy.
Tomatoes are not harmful, however you need to make sure your diet is as diverse as possible so you don't end up lacking other micro-nutrients. Also, you should, for best digestion, refer to the food combining chart.
Finally, 5 to 8 tomatoes a day is nothing in comparison of how many pounds of tomatoes are needed to make a simple pizza, which some people, on the SAD diet eat on a daily basis for instance. Thankfully I'm not one of them, and I like tomatoes raw rather than processed.
I would also like to add that tomatoes are very acid fruits, amongst the acid-iest fruits available, and this might also be an issue for some; again variety in the diet is the best way to neutralize your pH.