Thiamin. Plays a key role in the body's metabolic cycle for generating energy; aids in the digestion of carbohydrates; promotes growth & good muscle tone, essential for the normal functioning of the nervous system, muscles & heart, and stabilizes the appetite. A deficiency of Vitamin B1 may lead to the loss of appetite; weakness fatigue; paralysis & nervous irritability; loss of weight; insomnia; minor aches & pains; mental depression & constipation, and/or heart & gastrointestinal problems