As Pixie and ETF said, many fruits and veggies are GMO. (look it up)
The stuff you get in the store is crap compared to just buying seeds and growing it yourself. Let's take tomatoes for example. What you get in the store has been modified to have a long shelf life (marketability), strong skin (so they can be piled deep without bruising)...
If you bought some heirloom tomato seeds and grew them yourself, they'll taste better but you won't have the GMO effects.
To give you an idea, I planted some heirloom tomato plants in my garden last year. In general, they weren't as "pretty" as their GMO counterparts but they tasted much better. Some weren't good enough to harvest so I let them lay in the garden. This year, I have over 400 tomato plants growing, that I didn't plant. They just popped out of the ground from the heirloom plants from last year. I looked yesterday and I already have over 2000 tomatoes that will be ready for harvest in the next week or two.
I also planted heirloom versions of other plants. I didn't plant any this year but have pumpkin, sunflower and cucumber growing in the garden.
Just buy some heirloom seeds and skip the GMO crap.