Sugar added to milk for infants does not have an effect on mental ability, and sugar intake is not strongly associated with mental development. Sugar intake does not affect the intellectual development of infants, and has little to do with intellectual development. However, it should be noted that if too much sugar is consumed, it may cause dental caries, and in severe cases, symptoms such as recurrent toothaches may occur. If the intellectual development is slow, it may be related to genetic factors, the environment and pathological causes, such as Down’s syndrome, cretinism and hypothyroidism. Although adding sugar to milk for infants will not affect the child’s intelligence, it is not recommended to add sugar to milk, as the addition of sugar will affect the child’s appetite and is not conducive to the growth and development of infants.