Give a child and an adult the same drink, and the child will often prefer a much sweeter version. This is not merely the result of advertising or permissive parenting—the preference begins before either can exert much influence.
Newborns respond positively to sweetness, and children generally prefer stronger concentrations of sugar than adults. That preference gradually declines during adolescence, around the time physical growth slows.
The strongest evidence comes from an experiment involving 101 children aged five to ten and 76 adults. Children selected significantly sweeter solutions than adults. Taller children also preferred greater sweetness, and researchers found limited evidence connecting preference with a biological marker of bone growth. Experimental study
Well supported: humans begin life liking sweetness; children prefer more intense sweetness than adults; and this preference changes predictably with development. Genetics and experience also create substantial individual differences.
Plausible but debated: natural selection strengthened children’s sweet tooth because growing bodies require abundant energy. In ancestral environments, sweetness usually indicated valuable foods such as ripe fruit, breast milk or honey—not unlimited candy and soda. Avoiding bitterness may likewise have protected inexperienced young foragers from some plant toxins, although many nutritious foods are also bitter. Scientific review
The connection between sweetness and growth remains correlational, so it does not prove that energy needs caused the preference to evolve.
A child’s sweet tooth may once have guided a growing body toward scarce calories. Modern food manufacturers can now supply that ancient appetite with more sugar than evolution ever anticipated.
