Thiamine

Thiamine is a vitamin, also called vitamin B1. Vitamin B1 is found in many foods including yeast, cereal grains, beans, nuts, and meat. It is often used in combination with other B vitamins, and found in many vitamin B complex products. Vitamin B complexes generally include vitamin B1, vitamin B2 , vitamin B3 ,vitamin B5 , vitamin B6  (pyridoxine), vitamin B12  and folic acid. However, some products do not contain all of these ingredients and some may include others, such as biotin, para-aminobenzoic acid (PABA), choline bitartrate, and inositol.

 It is a nutrient that is not synthesized in the human body. Food sources of thiamine include whole grains, legumes, and some meats and fish. Grain processing  removes much of the thiamine content, so in many countries cereals and flours are enriched with thiamine. Thiamine is a building block required for energy production and glucose metabolism.

Thiamine is used to treat thiamine deficiency  which when severe can prove fatal. In less severe cases, non-specific signs include malaise, weight loss, irritability and confusions.

Reference  https://www.webmd.com/vitamins/ai/ingredientmono-965/thiamine-vitamin-b1

https://en.m.wikipedia.org/wiki/Thiamine