Vitamin B1, also called Thiamine, is 1 of 8 B vitamins that are water soluble. This means your body cannot store these vitamins like it can other vitamins so your daily diet must include foods that contain it, such as eggs, dairy, dark leafy vegetables, whole grains, and red meat, fish, or poultry. The benefits of Vitamin B1 (Jamieson) include how it can help you prevent complications in your nervous system, brain, heart, stomach, muscles, your nerve cells. Talk to your doctor before taking Vitamin B1 or any supplements, especially if you have certain medical conditions or you are taking other OTC or Rx meds.