What is the cause of too much iron in someone with Down syndrome?

One of the suppositions as to why iron might be harmful is based on the fact that people with Down syndrome have an excess amount of superoxide dismutase (SOD) in their cells, due to the extra 21st chromosome. The excess SOD is supposed to make more hydrogen peroxide available, which may react with iron to cause more damaging free radicals.

At the present time, the research on this topic is still questionable and certainly ongoing. There is no definitive evidence that this happens, so it's too early to say that all iron is dangerous. I would certainly not recommend a low-iron formula for any infant with Down syndrome, due to the high risk of iron deficiency anemia in this age group.

After the second year of life, my personal recommendation would be that there's no reason to avoid iron-fortified foods, but there's no reason for extra iron supplementation in vitamins unless there is a documented anemia from iron deficiency.

If you want to give your child a chewable vitamin and all your choices have some iron in them, pick the one with the lowest amount. (Caveat: Women with Down syndrome who are menstruating do need iron supplementation to avoid becoming anemic; they don't tend to eat enough red meat to make up for the monthly blood loss.)