A nutrient in the vitamin B complex that the body needs in small amounts to function and stay healthy. Thiamine helps some enzymes work properly, helps break down sugars in the diet, and keeps nerves and the heart healthy. It is found in pork, organ meats, peas, beans, nuts, and whole grains. Thiamine is water-soluble (can dissolve in water) and must be taken in daily. Not enough thiamine can cause a disease called beriberi (a condition marked by heart, nerve, and digestive disorders). Too much thiamine may help cancer cells grow faster. Also called vitamin B1.