In the past it was recommended that infants from birth to 4 months of age could receive a lower quantity of iron compared with those from 4 to 12 months of age. As such, several milk-based formulas (for example, Similac (Ross Pharmaceuticals) and Enfamil (Mead Johnson Pharmaceuticals)) were marketed under two varieties -- "low iron" and "high iron." (Some parents have inaccurately called "low iron" formulas "no iron" -- no such product exists.)
Pediatricians currently recommend that all children receive the iron content found in "high iron" formulas. It is not necessary to search for "high iron" formula brands. Unless the container clearly indicates that the brand is "low iron," all brands are manufactured with only the single "high iron" option. These include both milk-based as well as soy protein-based brands.
The "high iron" formulas are said in folklore to be more likely to cause gastrointestinal side effects, including increased gas and constipation, than other formulas or breast milk. Many studies have conclusively shown this is not true.