Zinc levels rising in infants, above TUL
had zinc levels above the recommended upper levels, report
researchers, who warn that increasing intakes may become excessive.
Zinc is essential for healthy immune function and growth in children and is also thought to play a role in brain function and mental performance. However too much zinc could damage copper status and have a negative effect on immune responses.
The researchers from University of California, Davis, studied data on zinc intake and other nutrients in almost 7500 non-breastfeeding pre-school children, from the Continuing Survey of Food Intakes by Individuals (1994-1996 and 1998), a nationwide survey conducted periodically by the US Department of Agriculture (USDA They also examined factors associated with zinc intake, such as copper intake.
The mean intakes of zinc by children under 1 year, 1-3 years old, and 4-5 years old were 6.6, 7.6, and 9.1 mg daily, respectively. Less than 1 per cent of children had usual zinc intakes below the adequate intake or estimated average requirement, write the researchers in the recent issue of the American Journal of Clinical Nutrition (vol 78, no 5, pp1011-1017).
More than 90 per cent of infants younger than six months exceeded the tolerable upper intake level for zinc. This decreased with age : 86 per cent of those aged 7-12 months, 51 per cent of 1-3 year-olds and 3 per cent of 4-5 year-olds had zinc levels above the TUL.
They also found that controlling for age and energy intake, zinc intake was greater in 1998 than in 1994 and was positively associated with participation in the Women, Infants, and Children Program and with the lowest income category.
The authors write : "The present level of intake does not seem to pose a health problem, but if zinc intake continues to increase because of the greater availability of zinc-fortified foods in the US food supply, the amount of zinc consumed by children may become excessive."
Increasing consumption of zinc-fortified foods such as breakfast cereals, infant formula and cereal bars seem to be the source of the additional zinc.
