- Thiamine (Vitamin B1) deficiency causes Beri beri, a disease affecting the nervous system (polyneuritis) and cardiovascular system. - Niacin (Vitamin B3) is also known as Nicotinic acid or Nicotinamide. Its deficiency causes Pellagra, characterized by symptoms often referred to as the "4 Ds": dermatitis, diarrhea, dementia, and potentially death. - Riboflavin (Vitamin B2) deficiency leads to ariboflavinosis, symptoms of which include Cheilosis (cracking of the lips and corners of the mouth) and Glossitis (inflammation of the tongue). - Biotin (Vitamin B7) is also known as Coenzyme R. Deficiency is rare but can cause skin conditions, hair loss, and neurological symptoms like hyperesthesia (increased sensitivity). - Cyanocobalamin (Vitamin B12) is essential for DNA synthesis and nerve function. Deficiency causes megaloblastic anemia, specifically pernicious anaemia when absorption is impaired (related to "antipernic factor" intrinsic factor).