A colouring is a substance added to processed food to colour it, compensating for colour lost in processing, enhancing natural colour, or giving an appealing hue. Colourings may be natural, such as beetroot red, turmeric, or caramel, or synthetic, such as tartrazine, each with an E number and regulated maximum levels following safety evaluation. They serve no nutritional purpose but strongly influence consumer acceptance, since colour shapes expectations of flavour. Some parents avoid certain artificial colours linked in studies to hyperactivity in susceptible children. Labels must declare colourings, letting shoppers choose according to their preferences.