APA Dictionary of Psychology

a group of water-soluble vitamins of different chemical makeup that function as coenzymes. Among the most important of these vitamins are B₁ (thiamine), B₂ (riboflavin), and B₃ (nicotinic acid), all of which help convert food into energy and are necessary for healthy skin, hair, muscles, and brain (with B₃ also essential for healthy blood cells and nervous system). Others include B₅ (pantothenic acid), which helps make lipids (fats), neurotransmitters, steroid hormones, and hemoglobin, and B₁₂ (cobalamin), which in interaction with folic acid assists in making new cells, breaking down some fatty and amino acids, protecting and encouraging growth of nerve cells, making red blood cells, and possibly lowering the risk of heart disease.