Several minerals, such as calcium and iron, and possibly zinc, reduce the absorption of manganese.³ Of these interactions, the link to iron may be the most important. In one study, women with high iron status had relatively poor absorption of manganese.⁴ In another report of manganese/iron interactions in women, increased intake of “non-heme iron”—the kind of iron found in most supplements—decreased manganese status.⁵ These interactions suggest that taking multi-minerals that include manganese may protect against manganese deficiencies that might otherwise be triggered by taking isolated mineral supplements, particularly iron.