The power of the tomato

In the last two weeks my husband has had pains in his mid left side every time after he eats. Sometimes very painful. As long as he lays on his back after the meal for about an hour and a half the pain seems to go away. Something he usually doesn't eat is tomatoes. I cut a bunch up to snack on for lunch with a little Italian dressing. The food wasn't ready for lunch yet so he ate quite  few of the tomatoes. After lunch he didn't experience the pain in his side. We don't know what the tomatoes did but he's eating a small amount everyday and so far no more pain. I think he is scared to stop eating them. There is no other symptoms.