What if you ate plenty of delicious food and yet had very little energy? That is how you might feel if you were severely deficient in any of the B-complex vitamins. Vitamin B1, along with B2, B12 and niacin are essential nutrients that play important roles in energy production, particularly in the metabolism of carbohydrates, fats and proteins. Without sufficient B1, you would feel weary, fatigued, and find it hard to function normally. The B vitamins are in a family of nutrients called coenzymes that help enzymes perform essential chemical reactions. This helps energy production, but also reactions critical to the function of neurotransmitters, hormones, digestive enzymes, mineral metabolism, and many more. Vitamin B1 helps to support the health of the central nervous system, cardiovascular system, pulmonary system, immune system and muscle function, which is why it is considered essential.