Can bread make your heart race?

This question is for my wife. A few months ago, she had to go to the hospital because she thought she was having a heart attack. Her pulse was 145. They gave her xanax and sent her home. She went to the doctor, telling her that her heart was racing for no reason. The dr did blood work and then put her on a beta blocker which seemed to help. Shortly after that, her gall bladder started acting up. For the next few months, waiting for the surgery, she noticed that every time she ate bread, her heart would race. We figured it had something to do with her gall bladder because after she had it removed, no more racing heart. To the point that the beta blocker was making her pulse and bp to low so she had to quit taking it. A few weeks ago, we found out she was pregnant, and once again, every time she eats bread, her heart races. She mentioned it to her dr and she just looked at her like she was crazy. So has anyone else had this problem? It really only seems to happen when she eats bread.