Vitamin B1, also called thiamine, has a wide spectrum of uses including metabolic reactions and forming adenosine triphosphate (ATP), an energy source every cell type in the body uses.Deficient B1 levels can lead to: Beriberi- a disease that causes heart damage, loss of mental alertness, and trouble breathingFatigueIrritabilityDepressionAbdominal discomfortDifficulty digesting carbohydratesCataractsMajor sources of vitamin B1 are: YeastFortified cereal grainsNutsBeans and legumesPork and organ meatsVitamin B1 deficiency can be more prevalent in people who are: AlcoholicsAnorexic Living with digestive disorders like Crohn's disease or celiac diseaseUndergoing kidney dialysis