Vitamin B1 is a water-soluble vitamin and is especially important for the correct functioning of nutritional and metabolic processes. It is essential for the growth and development of our cells as well as for correct cellular function as a whole. It is also very important for the correct functioning of our nervous system, brain activity and cardiovascular system. Its role is particularly important in the childhood period. Vitamin B1 is particularly abundant in nature. It is found in whole grains, legumes, yeast, eggs and fresh and dried fruit. A deficiency of vitamin B1 can cause disturbances in metabolism and normal cellular activity as well as nervous system diseases (beri beri, Wernicke-Korsakoff syndrome). There is no data on the effects of an excess of vitamin B1. A difficult condition to achieve also as a result of the fact that excesses of this active ingredient are generally easily expelled in the urine.